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Chinese herbal medicine combined with oxaliplatin-based chemotherapy for advanced gastric cancer: A systematic review and meta-analysis of contributions of specific medicinal materials to tumor response

Introduction: The incidence and mortality of gastric cancer ranks among the highest, and the 5-year survival rate of advanced gastric cancer (AGC) is less than 10%. Currently, chemotherapy is the main treatment for AGC, and oxaliplatin is an important part of the commonly used chemotherapy regimen for AGC. A large number of RCTs have shown that Chinese herbal medicine (CHM) combined with oxaliplatin-based chemotherapy can improve objective response rate (ORR) and disease control rate (DCR), reduce the toxic and side effects of chemotherapy. There is currently a lack of systematic evaluation of the evidence to account for the efficacy and safety of CHM combined with oxaliplatin-based chemotherapy in AGC. Therefore, we carried out this study and conducted the sensitivity analysis on the herbal composition to explore the potential anti-tumor efficacy. Methods: Databases of PubMed, EMBASE, CENTRAL, Web of Science, the Chinese Biomedical Literature Database, the China National Knowledge Infrastructure, the Wanfang database, and the Chinese Scientific Journals Database were searched from their inception to April 2022. RCTs evaluating the efficacy of CHM combined with oxaliplatin-based chemotherapy on AGC were included. Stata 16 was used for data synthesis, RoB 2 for quality evaluation of included RCTs, and GRADE for quality of synthesized evidence. Additional sensitivity analysis was performed to explore the potential anti-tumor effects of single herbs and combination of herbs. Results: Forty trials involving 3,029 participants were included. Most included RCTs were assessed as “Some concerns” of risk of bias. Meta-analyses showed that compare to oxaliplatin-based chemotherapy alone, that CHM combined with oxaliplatin-based chemotherapy could increase the objective response rate (ORR) by 35% [risk ratio (RR) = 1.35, 95% confidence intervals (CI) (1.25, 1.45)], and disease control rate (DCR) by 12% [RR = 1.12, 95% CI (1.08, 1.16)]. Subgroup analysis showed that compare to SOX, FOLFOX, and XELOX regimens alone, CHM plus SOX, CHM plus FOLFOX, and CHM plus XELOX could significantly increase the ORR and DCR. Sensitivity analysis identified seven herbs of Astragalus, Liquorice, Poria, Largehead Atractylodes, Chinese Angelica, Codonopsis, and Tangerine Peel with potentials to improve tumor response of oxaliplatin-based chemotherapy in AGC. Conclusion: Synthesized evidence showed moderate certainty that CHM plus oxaliplatin-based chemotherapy may promote improvement in tumor response in AGC. CHM treatment is safe for AGC. Due to the poor quality of included RCTs and small samplesizes, the quality of synthesized evidence was not high. Specific combinations of herbs appeared to produce higher contributions to ORR than the herb individually. Each of this seven above mentioned herbs has been shown in experimental studies to potentially contribute to the improvement of tumor response. To support this conclusion, these seven herbs are worthy of further clinical research. Systematic Review Registration: [http://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=262595], identifier [CRD42022262595].


Introduction
According to Global Cancer Statistics 2020, there were 1,089,000 new cases and 769,000 mortality cases of gastric cancer (GC) globally, ranked second of incidence and mortality rate of all malignant tumors of digestive system (Sung et al., 2021). The number of GC cases in China accounts for 43.9% of the global total. About 50% of GC patients were in advanced stage at the initial diagnosis. Advanced gastric cancer (AGC) has a poor prognosis, with a median overall survival (OS) of 10-12 months (Digklia et al., 2016), and the 5-year survival rate is no more than 10% (Song et al., 2017). AGC generally have distant metastasis and local infiltration, and 50% of recurrent patients were local lymph node positive (Peng et al., 2010). It is reported that the OS of patients with metastatic GC after palliative chemotherapy is only 7-15 months, and the 5-year survival rate is only 2% (Leong, 2005;Ajani et al., 2007). In recent years, the incidence and death of GC are on the rise. Therefore, AGC has become one of the main diseases endangering human life and health (Johnston et al., 2019).
Chemotherapy is the standard first-line treatment for AGC patients, and palliative chemotherapy has a statistically significant advantage over best supportive care in improving survival in AGC patients (Wagner et al., 2006). The NCCN guidelines recommend that combined chemotherapy containing platinum and fluorouracil is preferred for AGC patients (Ajani et al., 2022). Oxaliplatin is a third-generation platinum-type anticancer drug. Clinical studies have proved that it has a significant inhibitory effect on locally AGC or AGC, and its efficacy is no less than that of cisplatin (Ajani et al., 2016;Smyth et al., 2016;Yoshino et al., 2018). The median progression-free survical (mPFS) of first-line chemotherapy is 4-6 months and median overall survival (mOS) is 10-15 months (Van Cutsem et al., 2006;Cunningham et al., 2008;Koizumi et al., 2008;Kang et al., 2009). Moreover, oxaliplatin is better tolerated than cisplatin and has a better synergistic effect with fluorouracil (Al-Batran et al., 2008). Based on the above advantages, oxaliplatin has become the main platinum drug in AGC chemotherapy, which is used to form SOX, XELOX and FOLFOX regimens. However, peripheral neurotoxicity is the main side effect of oxaliplatin, which incidence of peripheral neurotoxicity is higher than that of cisplatin (63% vs. 22%), especially grade 3 or 4 neuropathy (Al-Batran et al., 2008;Cunningham et al., 2008). The targeted drugs approved for the treatment of AGC are mainly anti-angiogenic drugs, including trastuzumab and ramucirumab. The mOS of trastuzumab in the treatment of AGC patients with positive HER-2 is 7.9 months, but the incidence of anemia and visceral bleeding, two kinds of serious adverse events (AEs), is about 19% (Thuss-Patience et al., 2017). In addition, HER-2 overexpression only accounts for 15%-20% of AGC (Joshi et al., 2021), and the benefit in OS of other drugs is unclear, and the selection of targeted drugs is limited. There is no evidence supporting survival benefit of immunotherapy alone in patients with AGC (Shitara et al., 2018;Bang et al., 2019;Van Cutsem et al., 2021). Therefore, despite the variety of treatment options for AGC, chemotherapy is still the best choice for AGC, and chemotherapy drugs are constantly updated and iterated. However, obstacles such as serious AEs of chemotherapy, poor quality of life (QoL) and short survival of patients with AGC have not been well solved, and the treatment of AGC is still a major challenge.
CHM has been widely used in east Asia to fight against tumors for a long time. In particular, CHM combined with chemotherapy has advantages of synergistic efficacy and toxicity reduction, improving QoL and enhancing immune function (Cheng et al., 2021). A meta-analysis of 2,670 patients with AGC found that patients with astragaluscontaining Chinese medicine combined with platinumcontaining chemotherapy had better objective response rate (ORR) [risk ratio (RR) = 1.24, 95% confidence interval (CI): 1.15-1.34) ] and disease control rate (DCR) (RR = 1.10, 95% CI: 1.06-1.14), the AEs caused by chemotherapy were significantly reduced, and the QoL was significantly improved (Cheng et al., 2021). There was no previous meta-analysis of oxaliplatin-based chemotherapy regimen plus CHM, but some high quality clinical studies have demonstrated the important role of CHM combined with oxaliplatin. Yiqi Huoxue Jiedu formula combined with XELOX regimen could improve DCR (60.78% vs. 41.67%) (Hu, 2011). Shenlian capsules combined with SOX chemotherapy intervention in 157 patients with AGC, the ORR and DCR of the treatment group were 78.1% and 92.7%, respectively, while those of the control group were 66.4% and 79.9%, besides, which significantly reduced the incidence of neurotoxicity and other toxic and side effects (52.2% vs. 94.6%) and prolonged OS about 2.7 months (Diao et al., 2018). The ORR and DCR in the treatment group of Weifu formula combined with FOLFOX6 were significantly improved (ORR,70.0% vs. 26.7%;DCR,83.3% vs. 56.7%), and the KPS score was also improved (83.3% vs. 60.0%) (Fan et al., 2015). However, these individual studies are not enough to explain the clinical role of traditional Chinese medicine (TCM) in AGC. Evidence-based medicine should be used to comprehensively analyze existing clinical studies and to evaluate available evidence. Due to the complexity and diversity of Chinese medicine prescriptions, it is impossible to determine which CHM herbs play an important role to synergistic action with chemotherapy.
With the further development of basic research, the role and mechanism of TCM in inhibiting the division and proliferation of tumor cells, promoting the apoptosis of tumor cells, inhibiting the metastasis of tumor cells, and enhancing the curative effect with chemotherapy have been gradually revealed, laying a foundation for the effective application of anti-tumor Liu et al., 2020;Ren et al., 2020;Xiang et al., 2020;Zhang L. et al., 2021). Available experimental studies indicate that TCM compounds do have anti-tumor activity, but the more appropriate and accurate drug selection is still unknown. Therefore, future research will focus on finding individual herbs with special contributions to chemotherapy efficacy of AGC, and to improve survival benefit of AGC and precise selection of TCM.
There are several RCTs evaluated the efficacy and safety of CHM in AGC, but these clinical evidence were not systematically evaluated. Furthermore, whether CHM have a synergistic effect with oxaliplatin-based chemotherapy, the key component of the first-line treatment of AGC, also need further evaluation. The objective of this study was to systematically evaluate the available evidence of tumor response and safety of CHM combined with oxaliplatin-based chemotherapy in AGC. Furthermore, we performed sensitivity analysis of single herb and combination of herbs, to explore the potential anti-tumor effects of these herbs.
response evaluation criteria, WHO criteria, and RECIST criteria, the outcomes reported by these two criteria were considered homogeneous (Aras et al., 2016).

Search strategy
We searched PubMed, EMBASE, CENTRAL, Web of Science, the Chinese Biomedical Literature Database (CBM), the China National Knowledge Infrastructure (CNKI), the Wanfang database, and the Chinese Scientific Journals Database (VIP database). Searches were performed from the databases initiation to April 2022. The language restriction was English and Chinese. The search strategy was based on the combination of controlled vocabulary (MeSH terms and Emtree terms) and free-text terms. The terms of "Stomach Neoplasms," "Oxaliplatin," "Antineoplastic Combined Chemotherapy Protocols," "Herbal Medicine," "Medicine, Chinese Traditional," and "Drugs, Chinese Herbal" were used to develop the search strategy for PubMed, which is shown in Supplementary Material S2. Modifications to the search strategy were used with other databases.

Screening and selection
Search results were imported to EndNote 20. The titles and abstracts of retrievals were screened after duplicates removal, then full articles of potential trials were assessed for their eligibility. Screening and selection were independently and in duplicate performed by the review authors (YT and HW). RCTs that met the inclusion criteria were included. The process was summarized using a PRISMA flow diagram.

Data extraction
The following data were extracted from the included studies: 1) identification information (first author, year of publication); 2) general information (study setting, sample size, and duration of follow-up); 3) participants (clinical stage, age, and sex); 4) intervention details (name of CHM intervention, compositions, and duration); 5) comparison details (chemotherapy regimen, dose, frequency, and duration of treatment), and 6) outcomes details.

Quality assessment
The Risk of Bias 2 (RoB-2) tool was used to assess the methodological quality of included studies (Sterne et al., 2019). We evaluated included studies of quality of the randomization process, deviation from intended intervention, missing outcome data, outcome measurement, and selection of the reported result. The overall quality of RCTs were evaluated as low, some concerns or high RoB.

Evidence synthesis for RCTs
Stata 16 was used in data synthesis to perform a metaanalysis. The RR for dichotomous data with 95% CIs were evaluated. The random-effects model was used when synthesizing data for the meta-analysis. As for the outcomes reported with zero event, the Mantel-Haenszel methods were adopted. We quantified inconsistency by applying the I 2 statistic; a value of I 2 > 40% was considered important heterogeneity, and I 2 > 75% was considerable heterogeneity (Higgins et al., 2019). Subgroup analysis were performed according to the different regimens of chemotherapy that patients received, and to explore the source of heterogeneity if substantial heterogeneity existed. Publication bias of the cumulative evidence among individual studies was evaluated using a graphical method of funnel plot (Egger et al., 1997).

Sensitivity analysis
We performed sensitivity analysis to investigate the potential contributions of specific herbs to tumor response. Previous studies proposed that if a particular herb possessed anti-tumor effects, they would be reflected in the pooled effect estimates of the studies which interventions containing this herb (Chen et al., 2016a;Chen et al., 2016b). Sensitivity analysis of ORR will be performed for studies on herbs used in AGC, herbs, or combinations of herbs presented in two or more studies, and the following principles will be applied: 1) Studies containing the same herb or combination of herbs will be treated as one, and the pooled RR (95% CI) and I 2 will be calculated; 2) herbs or combinations of herbs will be excluded if there is no significant effect in the pooled results (95% CIs of RR overlap 1.0) and/or important heterogeneity exists between studies (I 2 ≥ 40%); 3) the RR results will be listed in ascending order with 95% CI, the number of studies and I 2 values; 4) the combination of herbs will be excluded when they have lower RRs than herbs alone; and 5) when herb combinations have higher RRs than herbs alone, they will be identified as potential examples of synergistic effects.

Quality of evidence
The quality of the cumulative evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. Study limitations, inconsistency, indirectness, imprecision, and publication bias were evaluated. Quality of evidence was classified as high, moderate, low, or very low quality (Guyatt et al., 2008). We presented our findings in a Summary of Finding table.

FIGURE 4
Forest plot of DCR.
Frontiers in Pharmacology frontiersin.org 14 outcomes could be influenced by knowledge of interventions patients received. The imbalanced missing data in two trials lead to the "High" risk in domain of missing outcome data, and in overall bias. The summary of RoB was shown in Figure 2.

The tumor response of CHM combined with oxaliplatin-based chemotherapy in AGC
Meta-analysis of 40 trials showed that CHM combined with oxaliplatin-based chemotherapy could increase the ORR by 35% [RR = 1.35, 95% CI (1.25, 1.45)]. The value of I 2 = 0 indicates that there was no statistical heterogeneity among these trials. The forest plot of ORR was shown in Figure 3. Meta-analysis of 40 trials showed that CHM combined with oxaliplatin-based chemotherapy could increase the DCR by 12% [RR = 1.12, 95% CI (1.08, 1.16)]. I 2 = 0 indicates that there was no statistical heterogeneity among these trials. The forest plot of DCR was shown in Figure 4.

The safety of CHM combined with oxaliplatin-based chemotherapy in AGC
Safety outcomes were reported in 37 trials. We evaluated the incidence of AEs of blood system, gastrointestinal reaction, hepatorenal toxicity, and peripheral neurotoxicity.

Peripheral neurotoxicity
Incidences of peripheral neurotoxicity were reported in 27 trials. Meta-analysis showed that compare oxaliplatinbased chemotherapy alone, CHM combined with oxaliplatin-based chemotherapy could decrease the incidence of peripheral neurotoxicity by 30% [RR = 0.70, 95% CI (0.61, 0.80)]. Forest plots of incidence of hepatorenal toxicity were shown in Figure 8.

Subgroup analysis
We performed subgroup analysis of the outcomes of tumorresponse, according to the different regimen of chemotherapy that patients received.

Sensitivity analysis
We performed sensitivity analysis to investigate the potential contributions of specific herbs to tumor response. Three trials which adopted multiple core prescriptions were excluded from sensitivity analysis, and we analyzed the composition of core prescriptions in other 37 trials that adopted single core prescription. There are 114 herbs in the formulas of included trials, 47 of these herbs were used only in one trial and were excluded from the sensitivity analysis. Among 67 herbs analyzed, 43 herbs were only used with other herbs as a combination, which means that when herb was used in several formulas, there was always an herb in the same formulas. RRs of the group of trials that included each specific herb or herb combination were calculated. Among 380 sensitivity analyses performed, 21 single herbs and 129 herb combinations were located, and 3 single herbs along with 227 herb combinations were excluded according to the predetermined principle.

Publication bias
We assessed the publication bias with a funnel plot and Egger test. The funnel plot was shown in Figure 9A p-value = 0.1197 in Egger test indicated that no serious publication bias was observed.

Quality of evidence
We assessed the quality of synthesized evidence of tumor response with GRADE approach. The results in subgroup analysis were adopted, since the subgroup of different chemotherapy regimen minimize the clinical heterogeneity. We got moderate to low quality of evidence, and the reasons to downgrade were that the majority of the evidence was from the trials with moderate methodological quality, and small sample size. The summary of findings was shown in Table 5.

Meta-analysis of trial results
Our study showed with a moderate certainty that compare with SOX, FOLFOX or XELOX regimen alone, CHM combined with SOX, FOLFOX or XELOX could significantly improve the ORR without heterogeneity, which has a practical guiding value for the clinical application of CHM synergistic chemotherapy regimen. In addition, we also found that although the relative effect of SOX regimen was lower than that of FOLFOX and XELOX, which was due to the higher anticipated absolute effects of SOX regimen alone than that of FOLFOX and XELOX, so the improvement was not particularly significant. When SOX combined with CHM, the anticipated absolute effects had increased to 60.5%, which was higher than about 50% of other regimens. The results of our study were consistent with another previously published metaanalysis of CHM combined with paclitaxel-based chemotherapy in the treatment of AGC . Compared with paclitaxel-based chemotherapy, TCM combined with paclitaxelbased chemotherapy could also significantly improve the ORR [RR = 1.39, 95% CI (1.24-1.57), I 2 = 12%]. But the prescriptions of CHM included in the above studies are not consistent, which brings more uncertain factors to the comparison.
In reducing the incidence of AEs, CHM combined with oxaliplatin-based chemotherapy showed consistent efficacy in leukopenia, thrombocytopenia, nausea and vomiting with paclitaxel-based chemotherapy, but had more improvement advantages in anemia, gastrointestinal reactions, diarrhea, hepatorenal toxicity and peripheral neurotoxicity. It is worth noting that both paclitaxel-based and oxaliplatin-based chemotherapy are clinically useful chemotherapy regimens that easily lead to peripheral neurotoxicities (Yamashita et al., 2021). However, inconsistent clinical outcomes occurred between these regimens. CHM prescriptions in our study were effective in reducing the incidence of peripheral neurotoxicity, indicating that different herbal combinations may have different effects in reducing Frontiers in Pharmacology frontiersin.org the incidence of AEs. Therefore, it is important to excavate the effects of herbs and their combinations which may affect the efficacy to guide clinical application. In addition, this study also found that the interventions of CHM was safe in AGC patients, and the participation of CHM did not increase the occurrence of AEs. Furthermore, in order to explore the effect of CHM on the survival time of AGC, we reviewed the following studies and hope that will provide a useful reference, which is also the focus for future studies. A cohort study that 1:1 matched in Taiwan found that CHM could improve the OS rate of GC and reduce the risk of death by 45% (Hung et al., 2017). Afterward, using propensity score matching according to 1:3 also found that regardless of short-term or longterm application of TCM, compared with non-users, it could effectively reduce the risk of death by 41% or 59%, and pointed out that the most frequently used single herbal medicine was Astragalus (11.8%), and the most frequently used formula was Xiangsha Liujunzi Decoction (15.5%) [Codonopsis pilosula, Largehead Atractylodes, Poria, Liquorice, Muxiang, Amomum villosum] (Shih et al., 2021). Interestingly, these single herbs or formulas were generally consistent with the listed herbs in our study. In addition, a meta-analysis evaluating the efficacy of Astragaluscontaining TCM combined with platinum-based chemotherapy for AGC suggested that compare with platinum-based chemotherapy alone, chemotherapy combined with Astragalus-containing TCM could improve ORR, DCR, 1 or 2-year survival rate, QoL and lower incidence of AEs (Cheng et al., 2021). These above studies strongly corroborated the credibility of the herbal compositions obtained in this study.

Analysis of TCM contribution
It is well-known that CHM formulas were prescriptions composed of varieties of herbs, which plays a complex and multiple effect role in clinical efficacy. Based on the characteristics of syndrome differentiation treatment, the CHM prescriptions issued by different physicians for the same disease may be different from others. Similarly, this unique treatment characteristic is significantly highlighted in this study: the specific herbs of interventions is inconsistent in clinical studies of different CHM treatments for AGC. It should be emphasized that the same herbs may be used in different studies, which provides an important basis for findings the special contribution of different herbs.
However, these herbs are not only focused on improving ORR, and perhaps some herbs pay more attention to the reduction of the occurrence of AEs to chemotherapy, or the improvement of QoL. Therefore, to eliminate the interference of other herbs, we applied sensitivity analysis to explore the effect of individual herbs on ORR in AGC one by one firstly. Then analyze the multi-herb combination containing the same herbs to further evaluate which specific herbs and their combinations are most likely to improve the ORR of chemotherapy for AGC.
Inferred to previous studies (Chen et al., 2016a;Chen et al., 2016b;Chen MH. et al., 2016), to analyze the results more cautiously, our selected herbs and compositions must have more significant differences, no heterogeneity, and equal or higher RRs within each level. Based on the above criteria, from the results of multiple sensitivity analyses, we identified seven herbs as potential effect of synergistic action with chemotherapy for AGC: Astragalus (n = 13), Liquorice (n = 23), Poria (n = 21), Largehead Atractylodes (n = 26), Chinese Angelica (n = 14), Codonopsis (n = 18), and Tangerine Peel (n = 17). Among them, Dandelion and Paris Polyphylla possessed the highest effect estimate (RR = 1.47) in individual herb analysis. In addition, this study also analyzed the combination of herbs. It is reported that the composition of Codonopsis and Liquorice, and the composition of Codonopsis, Liquorice, Largehead Atractylodes and Poria both significantly improved the ORR of TCM combined with paclitaxel-based chemotherapy, which also provided supporting evidence for our study . Surprisingly, some relatively high-frequency herbs such as Pinellia (n = 20), Acruginous Turmeric (n = 15), or some herbs with relatively high RR such as Dandelion [1.47 (1.17,1.83 1.46 (1.13, 1.88)] in the individual herb analysis were not included in the final combination. We found that compared to the ORR under multi-herb combinations, the above potential herbs may not show a consistent effect with other herbs under multi-herb combinations. Nevertheless, these herbs also have the potential to contribute to ORR, and we found that these individual herbs with relatively high RR were mostly combined with the above 7 herbs in multi-herb combinations showing higher ORR value. Therefore, these herbs can also be considered for subsequent development.
In addition, we also excluded some highly heterogeneous herbs, such as Panax notoginseng (I 2 = 73.56%), although commonly used in AGC, which seems to significantly reduce ORR [1.71,(0.84,3.48)], but only two studies were evaluated. Notably, no negative RRs emerged for any of the herbs or combinations, suggesting that these herbs did not impair the effects of chemotherapy.

Strength and limitations
To our knowledge, this is the first meta-analysis evaluating the efficacy and safety of CHM combined with oxaliplatin-based chemotherapy in AGC. Our study suggests that the synergistic treatment of CHM may be more TRR-improving on FOLFOX and XELOX regimens, and has high safety for clinical application. In addition, this study complied strict inclusion and exclusion criteria to exclude studies without a clear randomization method, which reduces the RoB in studies and improves the reliability of results. Therefore, quality of only one outcome was classified as low, and other qualities of evidence were moderate. There was also no serious publication bias.
At the same time, our study also has several limitations. Firstly, lacks multi-center, large-sample RCTs and some of the original study sample sizes are small, which causes bias in the results, which requires the publication of more high-quality clinical studies. Secondly, the included studies had an insufficient assessment of long-term survival indicators (OS, PFS), and our study showed that CHM could improve TRR in AGC, but whether it could translate into a benefit in long-term outcomes, also requires reassessment. In addition, CHMs are a part of TCM preparations, including Chinese patent medicines and TCM injections, and these preparation types should also be widely evaluated. Even if there have been studies on the antitumor efficacy of TCM preparations such as cinobufotalin (Sun et al., 2019) and brucea javanica oil injection  for AGC. A more comprehensive evaluation of CHM is needed to obtain more real, effective and safe evidence.
In addition, an obvious innovation point lies in exploring special herbs that have a synergistic action with chemotherapy on the ORR for AGC. The advantage of this methodology is based on the contribution of each herb to the contribution of ORR and is not simply based on the total frequency of herb emergence. A sensitivity analysis was chosen to identify the contribution of each herb in the study to ORR without missing it at a lower frequency. In summary, one cannot simply choose according to the overall frequency or the order of effect sizes of herbs in the dataset, but rather needs to consider the overall effect sizes at multiple levels simultaneously. For the selection process of final results, these herbs do not show improvement in ORR in only one clinical intervention study. In contrast, these herbs have shown consistent or higher effects in multiple studies and multiple combinations. Another limitation is that all possible combinations cannot be evaluated, and as the number of multiherb combinations increases, the number of combinations with a significant difference and no heterogeneity is smaller, the number of corresponding clinical studies and their sample size is also reduced, and the interpretation of the results should be more cautious. And there is no clear clinical trial to evaluate the clinical efficacy of this formula, and the corresponding RCT should be carried out for evaluation in the future.

Review of anti-gastric cancer mechanisms of seven selected herbs
Similarly, we cannot clarify that the listed herbs are all for improving the efficacy of chemotherapy, however, seven herbs have been used for AGC treatment in clinical in China (Cao et al., 2009). Among them, four herbs constitute a typical formula in China, Sijunzi decoction, which has been shown to reduce the nuclear accumulation and DNA-binding activity of β-catenin, thereby repressing cell growth and inducing apoptosis in human GC MKN74 and MKN45 cells . Network pharmacology and experimental validation suggested that Sijunzi decoction could inhibit tumor proliferation and angiogenesis by down-regulating the expression of VEGFA, iNOS, COX-2, and Bax/Bcl2 proteins in NCG-bearing mice with human gastric adenocarcinoma cell NUGC-4, regulate the PI3K/AKT pathway, and induce apoptosis (Ding et al., 2022). To further explore how seven herbs improve the short-term efficacy of platinum-based chemotherapy for AGC, we will review each herb to assess the mechanistic evidence of the specific anti-tumor activity. We found that the number of published mechanistic studies of these herbs was uneven, with Astragalus and Liquorice being more intensively studied.

Astragalus
Previous study has shown that Astragalus dose-dependently stimulates dendritic cells (DCs) to express Toll-like receptor 4 (TLR4), thereby enhancing cellular immune function, and inhibiting IκB-α protein expression and regulating NF-kB signaling pathways (Tian et al., 2014). Secondly, after coculture with MKN45 in vitro, MTT showed that Astragalus could reduce cell viability and induce apoptosis, and significantly reduce the number of cells. In vitro experiments also confirmed that Astragalus could significantly inhibit tumor diameter and weight, with a tumor inhibition rate of 57.1%. Another study also found that the aqueous extract of Astragalus could mediate antigen-presenting cells (APCs) to stimulate CXCR5 + Tfh-like cells to highly express IL-21, enhance humoral immunity and regulate CD8 + T cell activity (Dong et al., 2021).
In addition, the pharmacologically active components of Astragalus include polysaccharides, saponins and flavonoids, of which Astragalus polysaccharide (APS) is the most widely studied (Ma et al., 2002). In one study evaluating the anti-tumor activity of APS combined with adriamycin in human GC cell SGC-7901 and SGC-7901/ADR, the results showed that APS reduced cell viability and enhanced the rate of apoptosis in a time-dosage dependent manner, up-regulated p-AMPK and caspase-3 expression levels, induced apoptosis through the AMPK pathway, and improved the sensitivity of GC cells to adriamycin, suggesting that APS can be used as a chemosensitizer (Song et al., 2020). This paper speculated that the effect may be related to the decreased expression of MDR1, and the overexpression of tumor suppressor genes such as SEMA3F, P21 WAF1/CIP1 and FBXW7. Similarly, APS can also inhibit the expression of phosphorylated AKT (p-AKT) and MMP-9, and then inhibit the proliferation, migration and invasion of GC AGS cells through the AKT pathway, and also induce autophagy (Wu et al., 2018). In addition, APS also has a variety of immunoregulatory activities, such as regulating B lymphocytes and cytokines, especially inducing the activation and differentiation of splenic DCs, followed by the completion of Th2 to Th1 transition and enhancing the immune function of T lymphocytes (Liu et al., 2011).

Liquorice
A large number of bioactive components can be isolated from Liquorice, including triterpenoid saponins, flavonoids, isoflavones and chalcone (Asl et al., 2008). Glycyrrhizic acid (GA) is usually considered to be the main active component. The study has shown that GA can induce G1/S phase arrest of cell cycle and apoptosis by down-regulating the expression of cyclin D1, D2, D3, E1, E2, Bcl-2, survivin and p65, up-regulating the protein levels of Bax, PARP and pro-caspase-3, -8, -9. The proliferation of human GC cells (MGC-803, BGC-823, SGC-7901) has a time-and dose-dependent inhibitory effect by down-regulating PI3K/AKT signaling pathway .
Isoliquiritigenin (ISL) is a flavonoid extracted from Liquorice. Studies have shown that ISL can down-regulate Bcl-2 protein and p62, up-regulate Bax protein, caspase-3, Beclin 1 and LC3II/LC3I ratio, mediate apoptosis and autophagy of human GC MKN28 cells by inhibiting PI3K/ AKT/mTOR signaling pathway, thereby inhibiting cell proliferation, and reducing invasion and migration . ISL can also induce apoptosis in human GC MGC-803 cells by increasing free calcium concentration and decreasing mitochondrial transmembrane potential (Ma et al., 2001). However, licochalcone A (LCA), as a cytotoxic flavonoid, alone or in combination with 5-FU, increased the expression levels of Bax, PARP, tumor proteins 21, 27, 53 and caspase 3, and decreased the expression levels of Bcl-2, cyclin A, cyclin B and MDM2, which in turn blocked G 2/M cell cycle progression and induced apoptosis, inhibiting SGC7901 and MKN-45 cell proliferation in a time-dependent manner (Xiao et al., 2011;Lin et al., 2017). In addition, LCA can also increase the level of reactive oxygen species (ROS) and induce oxidative stress and apoptosis of BGC-823 cells through PI3K/AKT/mTOR and MAPK signaling cascades (Hao et al., 2015).
In addition, glycyrrhetinic acid (GA) can inhibit the viability of GC cells in a dose-and time-dependent manner, but its toxic and side effects limit its wide application, thus making many beneficial explorations on related derivatives . For example, 11-deoxy glycyrrhetinic acid can effectively inhibit GC formation by up-regulating p21 and down-regulating cdc2 and cyclin B1, mediating BID translocation from the nucleus to mitochondria, thereby inducing apoptosis and G2 phase arrest in GC cell (Lin et al., 2014). For another example, 18βglycyrrhetinic acid (18β-GA) can inhibit MMP-2 and MMP-9 activities in a dose-dependent manner, up-regulate E-cadherin expression and down-regulate vimentin expression, and reduce the metastatic potential of human GC cell line SGC-7901 cells through ROS/PKC-α/ERK signaling pathway and inhibition of EMT (Cai et al., 2018). In addition, new isoliquiritigenin (ISL) analogues (Huang et al., 2020), licochalcone A derivatives (LCA) (Shibata, 1994) can also provide more options for anti-GC drug research and development.

Poria
In vitro studies confirmed that Poria combined with oxaliplatin significantly decreased Snail, Twist, vimentin, and Frontiers in Pharmacology frontiersin.org N-cadherin mRNA and protein expression, significantly increased E-cadherin mRNA and protein expression, inhibited the EMT process, and decreased the invasion and migration of SGC7901 (Wang N. et al., 2018). This study also found that Poria could reduce the tumor volume, and improve the morphological parameters of GC cells. In addition, both dehydroebriconic acid and dehydrotrametenonic acid found from Poria sclerotia inhibited the growth of GC cells by arresting the G1 phase of the cell cycle, with LD (50) values of 63.6 and 38.4 microM, respectively (Mizushina et al., 2004).

Largehead Atractylodes
Atractylenolide (AT) is the main anticancer active ingredient of Largehead Atractylodes. Atractylenolide I (AT-I) has been found to inactivate the Notch signaling pathway by downregulating the protein and mRNA expression of Notch1, Jagged1, Hes1, Hey1 and CD44, inhibiting the sphere formation ability and cell viability of HGC-27, MGC-803 and MKN-45, thereby inhibiting the self-renewal ability and cell proliferation of GC stem-like cells (GCSC) and inducing apoptosis (Ma et al., 2014). A randomized controlled trial also verified the therapeutic effect of AT-1 on GC cachexia (Liu et al., 2008). Similarly, for Atractylenolide II (AT-II), Bax expression could also be up-regulated, and B-cell lymphoma 2 (Bcl-2), phosphorylated protein kinase B (p-Akt), and phosphorylated ERK (p-ERK) expression could be down-regulated, which induced apoptosis and inhibited proliferation and migration of HGC-27 and AGS in a concentration-and time-dependent manner by inactivating Ras/ERK and PI3K/Akt signaling pathways . AT-1 and AT-2 also inhibit Akt/ IκBα/NF-κB signaling pathway to play a role, thereby inhibiting gastritis to GC transformation (Amin et al., 2022). In addition, the aqueous extract of Largehead Atractylodes could inhibit the proliferation of BGC-823 and SGC-7901, decrease the mitochondrial transmembrane potential, and induce apoptosis and cell cycle arrest in a dose-and time-dependent manner (Zhao et al., 2014).

Chinese Angelica
Decursin is one of the active components of Chinese Angelica, which has been confirmed to down-regulate CXC chemokine receptor 7 (CXCR7) and Bcl-2 expression in a dose-dependent manner, mediate STAT3/c-Myc signaling pathway, induce apoptosis, and inhibit the proliferation, migration, and invasion of SNU484 and SNU216 (Kim et al., 2019). Another study by the same team also confirmed that Decursin could reduce cell viability, inhibited cell growth and induce G0/G1 arrest in vitro in a dose-and time-dependent manner (Kim et al., 2021). And by promoting the accumulation of LC3 and SQSTM1, inhibiting CTSC and E2F3 expression, and reducing the activity of lysosomal protein cathepsin C (CTSC), thereby inducing autophagic flux disorders. While in vivo studies, Decursin decreased the growth of tumor spheroids and patient-derived gastric organoids, and regulated the expression of CTSC and autophagy-related proteins, which in turn validated the in vivo experimental results.
In addition, a clinical data from Taiwan verified that Chinese Angelica could prolong the survival rate of GC patients [adjusted hazard ratio (HR) 0.72 [95% CI, 0.57-0.92] (p = 0.009)], and experimental studies also found that N-butylidenephthalide (BP), the active component of Chinese Angelica, could induce increased REDD1 expression, inhibit mTOR signaling, activate apoptosis through the mitochondrial pathway, and inhibit the proliferation and EMT of AGS, NCI-N87, and TSGH-9201 cells (Liao et al., 2018).

Codonopsis
Lobetyolin (LBT) and Lobetyol are the essential components of Codonopsis. The anti-GC activity of LBT mainly depends on the regulation of glutamine metabolism, the decrease of mRNA and protein expression of amino acid transporter alanine-serine-cysteine transporter 2 (ASCT2), the induction of apoptosis and the inhibition of GC cell proliferation (Bailly, 2021). Lobetyol induced apoptosis and G1/S phase cell cycle arrest in MKN45 cells by mediating MAPK signaling pathway in a time-and dose-dependent manner (Shen et al., 2016). Both can be further considered as potential anti-GC active ingredients. In addition, the Chinese medicine formula "Weikang Keli", containing Codonopsis and Largehead Atractylodes, can induce autophagic cell death in SGC-7901 cels. In vitro experiments showed that compared with the positive control of 5-FU, "Weikang Keli" aqueous extract could reduce the tumor volume in the GC model. Although the difference was not statistically significant, the motility, response sensitivity and food intake were increased (Huo et al., 2013).

Tangerine Peel
Nobiletin (Nob), a poly methoxy flavonoid extracted from Tangerine Peel, has been shown to inhibit MMP-9 activity in a concentration-dependent manner and to significantly reduce the total weight and number of disseminated nodules in a SCID mouse model (0.07g vs. 0.78g, p = 0.0059; 7.5 vs. 69.3/ body, p = 0.0001), thereby inhibiting the proliferation of TMK-1 cell with peritoneal disseminated nodule formation, which is beneficial in preventing GC metastasis (Minagawa et al., 2001). In addition, it could also up-regulate E-cadherin protein expression and down-regulate vimentin, fibronectin, MMP-9 protein and p-STAT3 expression in SGC-7901 cell, by inhibiting the STAT3 pathway, followed by inhibiting EMT .

Conclusion
Overall, CHM has a positive effect on improving oxaliplatinbased chemotherapy for AGC, which can improve short-term efficacy and reduce the incidence of AEs. In the sensitivity analysis of herbal medicines, it was found that herbal medicines such as Astragalus, Liquorice, Poria, Largehead Atractylodes, Chinese Angelica, Codonopsis, and Tangerine Peel had more advantages in increasing ORR. Previous mechanistic studies also confirmed their anti-GC activity, and the results of our study will provide beneficial evidence support for the combination therapy of CHM. Considering factors such as low quality of literature and insufficient sample size for clinical trials corresponding to shortlisted herbal medicines, quality of evidence was not high, definite conclusions cannot be drawn. More rigorously designed, large-sample, multi-center RCTs of herbal synergistic chemotherapy are needed in the future to better validate the action characteristics of CHM and its potential herbal medicines.

Author contributions
YT conceived this study. YT and HW registered the protocol and performed the search, screen, inclusion, and quality assessment of the included trials. HW and BX performed the evidence synthesis. YT, HW, and BX drafted the first version of this manuscript. XZ, GZ, YG, and TL provided critical revisions and edited the manuscript. JL and RG revised the manuscript. All authors read and approved the final manuscript for submission.

Funding
This work was supported by Scientific and technological innovation project of China Academy of Chinese Medical Sciences (grant number CI2021A01802).