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Efficacy and safety of apatinib plus docetaxel as the second or above line treatment in advanced nonsquamous NSCLC

Abstract Background: Apatinib is an oral small-molecule tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor 2 (VEGFR-2). Some clinical trials have demonstrated that apatinib is efficacious against advanced nonsquamous NSCLC. Objective: This study aimed to probe efficacy and safety of apatinib plus docetaxel, as the second or above line treatment, in advanced nonsquamous NSCLC. Design: Multicenter, prospective, single arm study. Setting: Three teaching hospitals centers in the Sichuan. Participants: Fourteen patients with stage IVA/B nonsquamous NSCLC had previously received at least 1 platinum-based chemotherapy regimen. Intervention: Patients who were enrolled between November 2016 and January 2018 were given docetaxel (75 mg/m2, i.v., d1) plus oral apatinib (250 mg/d), 4 weeks as one cycle, until disease progression or intolerance to adverse events (AE). Main outcome measures: The primary endpoint was progression-free survival (PFS). The secondary endpoints comprised objective response rate (ORR), disease control rate (DCR), overall survival (OS), and AE incidence rate. Results: All patients carried adenocarcinoma by pathological type. The median follow-up duration was 9.76 months. Out of 14 cases, 12 were evaluable, showing ORR of 33.33%, DCR of 66.67%, DCR of 50% in cases with brain metastasis, median PFS of 2.92 months (95% CI: 1.38–4.48), and 6-month OS of 80%. Primary AEs encompassed: leukopenia in 7 cases (58.33%), hand-foot skin reaction in 5 cases (41.67%), and diarrhea in 4 cases (33.33%). Among them, grade 3 AEs were: leukopenia in 4 cases (33.33%), and hand-foot skin reaction in 1 case (8.33%). No grade 4/5 AEs were reported. Univariate and multivariate analysis were conducted respectively for PFS and OS. These factors encompassed: gender, age, gene mutations, clinical stage, ECOG scores, quantity of metastatic foci, brain metastasis, and hand-foot skin reaction. Results demonstrated zero risk factors for PFS or OS. Conclusion: Apatinib plus docetaxel, as the second or above line treatment, is effective and safe against advanced nonsquamous NSCLC, with good tolerance profile. Trial registration: NCT03416231.


Introduction
Lung cancer is the main cause of cancer related death worldwide, severely endangering human health. [1] Non-small cell lung cancer (NSCLC) accounts for about 80% of lung cancer occurring in all patients, [2] which is mostly at the advanced stage upon diagnosis, with the median survival of less than 1 year. [3] Studies revealed the beneficial effect of chemotherapy and targeted therapy in a portion of NSCLC patients who experienced refractory first/ second line treatment, [4][5][6] but there lacks a standard third-line therapy regimen.
According to published reports over the last 20 years, the epidermal growth factor receptor (EGFR) has played an important role in regulating survival and cell proliferation in different types of cancer. [7] As in NSCLC EGFR is often deregulated by mutations, gene amplification or overexpression, [8] its inhibition effect has drawn a lot of attraction from researchers as an attractive therapeutic target. EGFR-TKIs such as gefitinib, icotinib and erlotinib have made great progress in treating NSCLC in clinic. A summary from 6 papers has demonstrated that the effect of erlotinib in the treatment of advanced NSCLC patients is superior to docetaxel in the terms of PFS, OS, and toxicity. [9] Hirsch et al have indicated that a subset of long-term NSCLC survivors who were receiving gefitinib had an excellent long-term safety profile. [10] Moreover, combining icotinib and chemotherapy leaded to improved PFS and OS in patients with untreated NSCLC harboring sensitive EGFR mutations, especially in those who harbored the EGFR exon 19 deletion. [11] Apatinib, an oral small-molecule tyrosine kinase inhibitor, binds with high affinity to VEGF receptor-2, preventing VEGF binding and activation. [12,13] Even though apatinib has not been internationally approved yet for lung cancer treatment, some clinical studies have already displayed efficacy in advanced nonsquamous NSCLC. [14] The results of the clinical trial demonstrated that the use of apatinib alone or combined with chemotherapy exhibits a high response rate and favorable tolerability profile in patients with advanced or metastatic squamous cell lung carcinoma. [15] Thus, combining apatinib with docetaxel may be a promising therapeutic schedule in the treatment of advanced NSCLC.
In this study, we enrolled 14 cases of advanced nonsquamous NSCLC, who had received at least 1 refractory platinum-based regimen before. The safety and efficacy of apatinib in combination with docetaxel in these patients were evaluated in this research.

Patient selection
Patients with advanced nonsquamous NSCLC were enrolled into this study, who were hospitalized into our department between November 2016 and January 2018. Those patients previously received at least 1 platinum-based regimen and the treatment failed.
All study subjects voluntarily participated in this trial, signed the informed consent, and complied with follow-up process. This work was approved by the Ethics Committee of Affiliated Hospital of North Sichuan Medical College. Clinical trial number: NCT03416231.

Patients evaluation
This was a multi-center, prospective, noncomparative study to determine whether apatinib administered in combination with docetaxel played a vital in patients with advanced NSCLC after firstor second-line chemotherapy failure. Efficacy assessment was conducted every 2 cycles. According to Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1, it was defined as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Objective response rate (ORR) referred to the proportion of CR+PR cases in evaluable patients. Disease control rate (DCR) referred to the proportion of CR+PR +SD in evaluable patients. AEs were monitored and recorded during trial, and classified into grade 1 to 5 according to Common Terminology Criteria for Adverse Events (CTCAE) Version 4.0.

Follow-up visit
Every patient was regularly followed-up by scheduled protocol in our institution. All patients were informed the AEs, physical examination, and laboratory tests including hepatorenal function, blood routine, and urine routine every 2 weeks by a thorough inquiry. Since starting therapy, follow-up by phone call or clinic consultation was conducted at least once per month to collect information on survival status, AEs, and subsequent treatment after disease progression. It was lasted until death or patient dropping-out or the end of the study. The detailed information of survival status from each follow-up was documented in the follow-up form. Progression free survival (PFS) referred to the time interval between therapy start and first onset of disease progression or death caused by any reason (whichever occurred first). Overall survival (OS) referred to the time interval between therapy start and death caused by any reason. The cut-off date for follow-up study was December 28, 2017, and the median follow-up duration was 9.76 months.

Statistical analysis
Kaplan-Meier method was adopted for survival analysis, and statistical software SAS9.2 was used for programming and computing. Two-tailed test was applied, with P < .05 designated as statistical significance, and 95% confidence interval (CI) was applied. A Cox proportional hazards model was adopted to analyze risk factors for PFS and OS. Chi-square test was used to detect DCR and ORR. Descriptive statistics was adopted for analysis of safety assessment, and AEs taking place during trial were described in the table.

General information of patients
Fourteen cases of advanced nonsquamous NSCLC were enrolled into this study who were hospitalized into our department between November 2016 and January 2018. For 2 patients failed to make a return visit, only 12 patients were evaluable. These patients included 4 males and 8 females, at the age range of 36 to 76 years (median age of 50 years). The pathological type in all cases was adenocarcinoma, 11 cases harboring wild-type EGFR while 1 case with mutated EGFR (exon 20 insertion mutation). 4 cases were at stage IVA while 8 cases at stage IVB. ECOG analysis displayed score 1 in 9 cases while score 2 in 2 cases and score 3 in 1 case. 5 cases had no more than 2 metastatic foci while 7 cases with more than 2 metastatic foci, in whom 2 cases harbored brain metastasis while 10 cases without. Eight patients have pleural effusion. Treatment histories were: 2 cases with brain metastasis previously received head radiotherapy, and 3 cases previously received lung radiotherapy, and 2 cases previously received analgesic radiotherapy for bone metastasis. As shown in Table 1, regimen of apatinib plus docetaxel was second line treatment in 3 cases while third line treatment in 5 cases and fourth line treatment in 4 cases.

Treatment effectiveness
In all enrolled cases, 12 (Table 4). However, hand-foot skin reaction was positive related to the DCR of the enrolled patients (Table 5).

Discussion
At present, platinum-based dual drug regimen is the standard chemotherapy for NSCLC, and targeted therapy can improve survival in patients who harbor mutations of sensitive genes, such as epidermal growth factor receptor (EGFR). [16,17] However, there lacks determined therapy regimen for advanced NSCLC patients who have experienced refractory first/second line chemotherapy, peculiarly those carrying no mutations of sensitive genes. Therefore, researchers launch clinical studies targeting those patients, including our study reported here. In a multicenter randomized and controlled trial reported by Shepherd and colleagues, [18] 204 patients with stage III/IV NSCLC, who had previously received at least 1 regimen of platinum-based chemotherapy, were randomized to single docetaxel 100 mg/m 2 group (49 cases), single docetaxel 75 mg/ m 2 group (55 cases), and optimal support treatment group (100 cases). Results demonstrated: single docetaxel was superior over the optimal support treatment in time to progression (TTP) and in median OS, respectively 10.6 weeks vs 6.7 weeks (P < .001) and 7.0 months vs 4.6 months (P = .047 by long-rank test). Notably, docetaxel 75 mg/m 2 was markedly superior to the optimal support treatment, reflected by median OS of 7.5 months vs 4.6 months (P = .010 by long-rank test) and 1-year OS of 37% vs 11% (P = .003 by Chi-square test). The primary AEs in docetaxel 75 mg/m 2 group included grade 3/4 leukopenia (37 cases, 67.27%) and diarrhea (20 cases, 36.36%). For these reasons, the dose (75 mg/m 2 ) of docetaxel were selected in our study.
Compared with above 2 trials, our study presented higher ORR (33.33%) and DCR (66.67%). Even though median OS was not available yet, 6-month OS was 80%, implying a trend of longer OS in apatinib plus docetaxel regimen. We speculate it might relate to the antitumor performance of both drugs. Angiogenesis is the key element for malignant tumor growth, and sustained angiogenesis closely associates with tumor initiation/ development/metastasis. [20,21] According to reference, over 50% of lung cancer had VEGF overexpression, which was correlated    Table 3 Clinical characteristics of the study population (n = 12). with poor outcome. [22,23] Apatinib could highly selectively compete for the ATP-binding site of intracellular VEGFR-2 and block its downstream signal transduction, thereby playing an antitumor part via robust inhibition of tumor angiogenesis. [24,25] In addition, apatinib can reverse multidrug resistance (MDR) of tumor cells mediated by multidrug transporter protein ABCB1 (pglycoprotein) via suppressing its activity in pumping out chemotherapy drugs, hence improving chemotherapy efficacy. [26,27] This promotive effect of apatinib on chemotherapy efficacy was also revealed by drug kinetics in a NSCLC mouse model. Interestingly, a study from Wang et al [28] displayed disparity to the therapeutic time window shown in other antiangiogenesis agents: the efficacy of synchronous apatinib with chemotherapy drugs was superior over the one in sequential administration. Data of our study as well favors the treatment modality of apatinib plus chemotherapy. Nonetheless, the specific antitumor mechanism underpinning combinatory therapy remains to be elucidated, and further exploration is needed to delineate the dose and frequency of combinatory drugs. Median PFS in our study was 2.92 months, shorter than the counterpart from above trial of single apatinib medication. It is worth noting that 2 trials showed divergence in enrolled patients' conditions and in medication methods. In our study, all patients were at stage IV and harbored multiple metastasis, involving important organs of the brain, lung, and liver; disease progressed even after multi line treatment; most patients carried wild-type EGFR, which imposed limitation on treatment options. Many researches have indicated that apatinib or other anti-angiogenic drugs combined with EGFR-TKI are effective in the treatment of NSCLC with sensitive gene mutations. [29,30] In this study, 11/12 (91.7%) patients have no EGFR mutation and did not receive EGFR-TKI therapy. However, in the research of Zhengbo Song, patients harboring EGFR mutation take a proportion of 16.7%. Besides that, the pathological types of the patients were all adenocarcinoma in our study, which was different from patients consisted of 30/42 (71.4%) adenocarcinoma in Zhengbo Song study. Furthermore, the dose of apatinib (250 mg) in this research is lighter than Zhengbo Song research (500 mg). In these regards, survival duration was estimated to be short.

Variables
Overall drug tolerance in our study is good. Primary AE encompassed: leukopenia in 7 cases (58.33%), hand-foot skin reaction in 5 cases (41.67%), diarrhea in 4 cases (33.33%), vomiting in 4 cases (33.33%), proteinuria in 3 cases (25%), and hypertension in 2 cases (16.67%). Among them, grade 3 AEs were: leukopenia in 4 cases (33.33%), hand-foot skin reaction in 1 case (8.33%). No grade 4/5 AEs were reported. In a randomized, double-blind, controlled phase III trial, [31] 176 patients with advanced gastric cancer and gastroesophageal junction cancer were treated with apatinib 850 mg qd monotherapy. Grade 3 to 4 AEs mainly included: leukopenia in 3 cases  (1.7%), hand and foot skin reaction in 15 cases (8.5%), diarrhea in 2 cases (1.1%), proteinuria in 4 cases (2.3%), and hypertension in 8 cases (4.5%). Compared with the above results, except for the increase of leukopenia, the occurrence of other grade 3 to 4 AEs in this study was reduced. The reason may be that in this study, lower apatinib dosage reduced the occurrence of AEs, but chemotherapy increased the number of hematological AEs. Liu et al [32] have found that in patients with advanced gastric cancer treated with apatinib alone, AEs such as hypertension, hand and foot skin reaction and proteinuria were good predictors of efficacy. In this study, the efficacy of patients with severe AEs was not better than those who have no severe AEs (Table 5). It may because docetaxel was combined with low dosage of apatinib in our experiment. This research indicated that serious AEs (foot-hand skin reaction and leukopenia) was not related to patients' age, PS score and number of treatment lines (Tables 6 and 7). This scenario is similar to results of abovementioned trials: combinatory drugs presented no increase in AE severity or categories. Grade 3/4 AE incidence was low, and all patients showed tolerance after symptomatic management. Therefore, it is rational to encourage further exploration on the feasibility of increased apatinib dose for boosting the therapeutic effectiveness of combinatory therapy. Univariate and multivariate analysis were conducted respectively for PFS and OS. These factors encompassed: gender, age, gene mutations, clinical stage, ECOG scores, quantity of metastatic foci, brain metastatic, and hand-foot skin reaction.
Results displayed zero risk factors for PFS or OS. Noticeably, conditions of 2 cases with brain metastasis were: cerebral lesion size reduced in one case (PR); in the other case, the original cerebral lesion stabilized while new lesion emerged (PD). It is consistent with the change trend observed in single apatinib medication for NSCLC by Xu et al [33] : in 7 cases of brain metastasis, 1 case had a reduction in cerebral lesion while 3 cases with stable cerebral lesions (head radiotherapy effect could not be excluded). In another clinical trial without adoption of radiotherapy, apatinib plus irinotecan demonstrated effectiveness in malignant glioma relapsing after chemotherapy. [34] Our study as well suggests apatinib could control cerebral lesions, that probably attributes to this small-molecule tyrosine kinase inhibitor penetrating through the blood brain barrier (BBB) and suppressing tumor. Given those 2 patients of our study had previously received head radiotherapy, and radiotherapy is known to inhibit tumor and alter BBB permeability, [35] further study is still required to illustrate the inhibitory effect of apatinib on brain metastasis.
In summary, our study preliminarily demonstrated the therapeutic effectiveness of apatinib plus docetaxel, as the second or above line treatment, in advanced nonsquamous NSCLC, and displayed good tolerance of patients. It could be an alternative multi line treatment option for patients harboring wild-type EGFR or brain metastasis. Based on these results, prospective randomized and controlled trials are expected to further validate the effectiveness and safety of combinatory drugs, and to Table 6 Clinical characteristics and grade 3 or above hand-foot skin reaction.  gradually explore the optimal modes of combinatory medications.