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Evaluation of different staging systems and prognostic analysis of nasal-type extranodal NK/T-cell lymphoma based on consistent LVDP chemotherapy regimen

Highlights • The LVDP chemotherapy regimen was effective and safe for nasal-type ENKTL.• The CMT yielded better survival outcomes than CT alone in nasal-type ENKTL.• The CASS had a better survival discrimination than the AASS.


Introduction
Nasal-type extranodal NK-T-cell lymphoma (ENKTL) is an Epstein-Barr virus (EBV) associated, aggressive non-Hodgkin lymphoma [1]. This disease has a remarkable geographical distribution, with a particularly high incidence in East Asia compared with Europe and North America [2,3]. In China, it accounts for 11% of all malignant lymphomas [4].
Unlike other kinds of lymphomas, NK/T cell lymphoma is almost exclusively extranodal, and about 80% of cases occur in the nasal or paranasal area [1,5]. Survival of patients with ENKTL has been markedly improved by using L-asparaginase-based chemotherapy regimens and the development of radiotherapy technology. However, patients are currently staged and treated primarily depending on the Ann Arbor staging system (AASS), which was originally established for Hodgkin Lymphoma [6]. Patients are classified into one of four stages (I-Ⅳ), each with a distinct survival outcome. According to the AASS, most patients (70-90%) have early-stage disease (stage I/II) at diagnosis, and advanced stage (III/Ⅳ) is uncommon. Due to unbalanced distribution of patients, the predictive accuracy of this staging system has been shown to be limited for ENKTL [5]. The Prognostic Index for Natural Killer lymphoma with EBV (PINK-E) is a routine prognostic system for patients with ENKTL, which consists of five clinical factors (age older than 60 years, stage III/Ⅳ of AASS, distant lymph node involvement, non-nasal-type disease, and EBV-DNA). Based on the PINK-E model, most early-stage patients are classified into the low-risk group, but a significant difference is not found for OS and PFS among the low-risk and the intermediate-risk group (p = 0.068 and p = 0.079, respectively). PINK-E could not predict prognosis for patients with ENKTL [6]. Therefore, a new staging system and optimal prognostic model are needed for extranodal nasal-type NK/T-cell lymphoma.
The Chinese Southwest Oncology Group and Asia Lymphoma Study Group (CA) staging system (CASS) is a new staging system, which was established in 2020 based on anatomic factors [7]. Stage I is defined as primary tumor localized to the nasal cavity or nasopharynx without local structures and regional lymph node involvement; stage II is defined as primary tumor localized to the nasal cavity or nasopharynx with local structures involvement without regional lymph node involvement; stage III is defined as primary tumor with regional lymph node involvement; and stage Ⅳ is defined as involvement of distant lymph node regions or lymph node regions on both sides of the diaphragm or disseminated involvement of one or more extralymphatic organs or tissues [7]. According to the CASS, the proportions of patients classified as stages I through IV are 27.4%, 35.2%, 18.7%, and 18.7%, respectively [7]. The CASS distribution for these patients is more symmetrical than AASS. Most early-stage patients defined by AASS are categorized as stage III by CASS. As a result, the CASS is better in stratifying survival than the AASS. However, heterogeneous chemotherapy regimens may have an impact on this result. Therefore, we conducted a retrospective study for comparing the value of different staging systems in nasal-type ENKTL based on the first-line, consistent LVDP chemotherapy regimen.

Patients
We conducted a retrospective study for patients with newly diagnosed nasal-type ENKTL from January 2012 to January 2017. The inclusion criteria were: (1) pathologically and immunohistochemically confirmed as nasal-type ENKTL based on the 2008 World Health Organization (WHO) classification of lymphomas [8]; (2) received at least two cycles of LVDP chemotherapy with or without radiotherapy; (3) sufficient clinical and laboratory data for staging and survival analyses; and (4) absence of other malignancies. Patients with non-nasal-type ENKTL were excluded. This retrospective analysis was approved by the biomedical research ethics committee of our hospital (ID of ethics approval: SCHX-2020-1039).
Clinical and laboratory data before treatment were collected for analysis and included the following: age, sex, Eastern Cooperative Oncology Group performance status (ECOG) score, presence of B symptoms, complete blood cell count (CBC), lactate dehydrogenase (LDH), plasma EBV DNA, and bone marrow examination including biopsies. Computed tomography (CT) of the head, neck, chest, abdomen, and pelvis; and positron emission tomography/computed tomography (PET/CT) scans were applied for staging. PET/CT was also used for response assessment. PINK-E scores were calculated in this study. Local tumor invasion (LTI) was defined as paranasal involvement or bone destruction or skin involvement according to the previous study [9]. Regional lymph node (RLN) involvement was defined according to definition of N1, N2, or N3 in tumor-node-metastasis (TNM) system. PINK-E, prognostic index of natural killer lymphoma with Epstein-Barr virus; RLN, regional lymph node; RTFCT, radiotherapy followed by chemotherapy; WBC, white blood cell.

Table 2
The short-term efficacy of the LVDP chemotherapy in different staging systems. Abbreviation: AASS, Ann Arbor staging system; CASS, CA staging system; CR, complete response; ORR, objective response rate; PD, progressive disease; PR, partial response; SD, stable disease.

Treatment
Except for 21 patients who received LVDP chemotherapy alone, a total of 184 patients received LVDP combined with radiotherapy. Of them, 129 patients received chemotherapy sandwiched radiotherapy (CTSRT) (patients received radiation after 2-3 cycles of LVDP chemotherapy, then continued to receive 2-3 cycles of chemotherapy after radiotherapy), 56 patients received chemotherapy followed by radiotherapy (CTFRT), and only one patient received radiotherapy followed by chemotherapy (RTFCT), due to nasal bleeding. The LVDP regimen was repeatedly given every 21 days as follows: L-asparaginase (5500IU/ m 2 intravenously on days 1-5), etoposide (80 mg/m 2 intravenously on days 1-3), dexamethasone (40 mg/day intravenously on days 1-4), and cisplatin (25 mg/m 2 intravenously on days 1-3). Before each cycle, an Lasparaginase skin test was administered; if the result was positive, Lasparaginase was replaced by pegaspargase (3750 IU intramuscularly on day 4). The median number of LVDP cycles was four (range, 2-8). As for radiotherapy, involved fields radiation was performed according to the guidelines of the International Lymphoma Radiation Oncology Group [10]. The median dose of radiotherapy was 50.4 Gy (range, 44-60 Gy).
At initial diagnosis with early-stage ENKTL according to AASS, patients received the LVDP regimen combined with involved-field radiation therapy (IFRT). At initial diagnosis with advanced stage ENKTL according to AASS, patients received consolidation radiation therapy of the primary tumor site or local residual lesion after completing planned chemotherapy. In addition, patients could receive hematopoietic stem cell transplantation (HSCT) after achieving CR or PR. Due to a lack of consensus, treatment methods varied and depended largely on physician choice.

Efficacy evaluation
All patients underwent efficacy assessment. The treatment efficacy was assessed based on the response criteria of malignant lymphoma and included complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD) [11]. The objective response rate (ORR) was defined as the proportion of patients with CR or PR. OS was defined as the time from the date of diagnosis to death or the last follow-up. OS after first relapse or progression was defined as the time from the date of disease recurrence or progression to death or the last follow-up. PFS was designated as the time from the date of diagnosis to the date of disease recurrence, progression, or any-cause death.

Toxicity evaluation
Toxicities were evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. All toxicity data came from physical examinations and blood tests (including CBC, liver and kidney function).

Statistical analysis
Statistical analysis was performed by SPSS version 22.0 (SPSS Inc, Chicago, IL). All categorical variables were presented through frequency with percentage, and the chi-square test was applied to identify associations between categorical variables. Survival results were performed via the Kaplan-Meier method, and the Log-Rank test was used to compare survival curves. Univariate and multivariate Cox regression analysis were used to identify independent prognostic factors for nasaltype ENKTL. We used receiver operating characteristic (ROC) curves to compare the sensitivity and specificity of different staging systems. If the two-sided P-value was less than 0.05, it was considered statistically significant.

Survival of patients with nasal-type enktl after first relapse or progression
After the last follow-up, total of 79 PFS events were recorded. During the initial therapy, 30 patients experienced PD. After the initial therapy, 49 patients experienced disease recurrence. The median OS after first relapse or progression was 3 months, and the 5-year OS after first relapse or progression in patients with nasal-type ENKTL was 17% (Fig. 3). At the last follow-up, 14 patients after the first relapse or progression were still free of disease. Of them, six patients underwent HSCT (auto-HSCT, n = 4; allo-HSCT, n = 2) after receiving SMILE (dexamethasone, methotrexate, ifosfamide, L-asparaginase and etoposide) chemotherapy, six patients received P-Gemox (pegaspargase, gemcitabine and oxaliplatin) combined with IFRT, one patient received anti-PD-1 antibody as maintenance treatment after receiving SMILE, and one patient received chidamide as maintenance treatment after receiving P-Gemox.

Prognostic factors
To explore the correlations between clinical variables and survival outcomes of nasal-type ENKTL patients, we conducted univariate and multivariate Cox regression analysis to identify independent prognostic factors. The clinical variables that potentially had an impact on the OS and PFS of patients were shown in Table 3    Using all of the variables established as important in univariable analysis, we performed a multivariable analysis to determine potential independent predictors for OS ( Table 4). The outcomes showed that only BM involvement at diagnosis (HR, 3.109; 95% CI, 1.021-9.466; p = 0.046) was an independent prognostic factor for OS for nasal type ENKTL. In terms of PFS, an independent prognostic factor was EBV-DNA positive (HR, 0.708; 95% CI, 0.526-0.952; p = 0.022).

Toxicity
Overall, the LVDP regimen was tolerable. Treatment-related toxicities were listed in Table 5. Most toxicities were grade 1/2. The most common toxicity was hematologic toxicity. Of these, the most frequent grade 3/4 hematologic toxicity was leukopenia (n = 57, 27.8%). 18 of them presented with fever, and, of these, only 2 patients had blood infections, which were successfully treated by antibacterial therapy. The most frequent grade 3/4 non-hematological toxicity was increased transaminases, which was observed in 7 (4.5%) patients. Eighteen patients experienced dose reduction or chemotherapy delay because of hematologic toxicity (n = 14) or increased transaminases (n = 4). No pancreatitis or treatment-related death was reported.

Discussion
In this study, we retrospectively analyzed different staging systems and the efficacy of LVDP for 205 patients with nasal-type ENKTL. Our results found that the LVDP combined chemotherapy regimen was effective for nasal-type ENKTL with mild toxicity. In Cox regression analysis of prognostic factors for survival, bone marrow involvement was correlated with poor OS, and EBV DNA positive in peripheral plasma was associated with worse PFS. Further study showed that the CASS better discriminated survival for patients with nasal-type ENKTL than the AASS and PINK-E.
In recent years, due to anthracycline-resistance, L-asparaginasebased regimens have demonstrated promising efficacy for ENKTL [12][13][14][15][16]. Kwong et al. reported a SMILE regimen that yielded a 5-year OS of 50% and a 4-year PFS of 64% in newly diagnosed ENKTL patients [17]. In a retrospective study to evaluate the efficacy and safety of GELOX (L-asparaginase, gemcitabine and oxaliplatin) or P-Gemox for ENKTL, a 3-year OS of 65.2% and PFS rate of 57% were observed [18]. In a prospective clinical trial in China, 165 patients received P-Gemox plus thalidomide or AspaMetDex (L-asparaginase, methotrexate and dexamethasone), and the 3-year PFS and OS rates were 61.4% and 63.4%, respectively [19]. Additionally, in a large-scale, multicenter study, Qi reported the survival outcomes of 1351 ENKTL patients based on non-anthracycline chemotherapy and reported a 5-year OS and PFS of 68.9% and 59.5%, respectively [20]. In our report, we found that treatment with LVDP achieved an ORR of 81.2%, with 58.5% of patients Abbreviation: BM, bone marrow; EBV, Epstein-Barr virus; ECOG PS, Eastern Cooperative Oncology Group performance status; Hb, hemoglobin; LDH, lactate dehydrogenase; LTI, local tumor invasion; PINK-E, prognostic index of natural killer lymphoma with Epstein-Barr virus; RLN, regional lymph node; WBC, white blood cell. * indicates significant difference at the 5% level.
Radiotherapy combined with chemotherapy plays a key role in nasaltype ENKTL [7]. In our study, about 90% patients received chemo-radiotherapy after initial diagnosis, and their survival outcomes were better than those of patients who received chemotherapy alone. This result was consistent with previous studies [22,23]. Vargo et al. reported that the omission of radiotherapy was associated with poor survival in patients with early-stage ENKTL [22]. In another restropective study from the International T-cell Lymphoma Project, radiotherapy combined with chemotherapy for early-stage ENKTL yielded better survival outcomes than chemotherapy alone (p = 0.045) [23]. In addition, more than half of patients (129/205) with nasal-type ENKTL received "Sandwich" LVDP chemo-radiotherapy and achieved promising results, including an ORR of 88.4%, 3-year PFS of 72.8% and 3-year OS of 81.4%. The ORR and survival outcomes were comparable to previous studies for ENKTL. In a clinical trial, 66 patients with early-stage ENKTL received "Sandwich" LVD and RT. The ORR was 88.5%, the 2-year PFS and OS were 80.6% and 88.5%, respectively [24]. In another multicenter study, 173 newly diagnosed stage I/II ENKTL patients received concomitant chemoradiotherapy. The ORR was around 90% and the 5-year OS plateaued at 72%− 74% [25]. In a recent report, 202 patients with early-stage ENKTL received sequential P-Gemox and radiotherapy, and the 3-year PFS and OS were 74.6% and 85.2%, respectively [26]. In summary, our results show that "Sandwich" LVDP chemo-radiotherapy is a potential option for nasal-type ENKTL.
Although the specific mechanism is still unclear, EBV is closely related to the pathogenesis of ENKTL, and plasma EBV-DNA has been considered as an important prognostic factor [6,27,28]. The level of plasma EBV DNA decreased when the treatment effected, and the level increased when disease relapsed [29]. Consistently, EBV-DNA was an independent prognostic factor for PFS (p = 0.022) in our report. In addition, we showed that bone marrow involvement was an independent prognostic factor for OS in our study. Bone marrow involvement at initial diagnosis is uncommon in ENKTL, but it develops within the course of disease in 2-12% of patients [30,31]. These patients likely develop a major complication, hemophagocytic syndrome (HPS). When it occurs, it is correlated with poor survival (median survival from 26 to 40 days). In our study, we showed that bone marrow involvement was an independent prognostic factor for OS. Due to the rarity of cases with bone marrow involvement, further study is needed to validate the prognostic value of it in nasal-type ENKTL.
Currently, the optimal prognostic system for ENKTL remains undefined. Several studies have established different prognostic models [5,6,32,33]. The international prognostic index (IPI) was established based on anthracycline-based chemotherapy in 1993 and is used for all non--Hodgkin's lymphoma, not exclusively for ENKTL [32]. The Korean prognostic index (KPI) and Nomogram-revised risk index (NRI) were established for ENKTL in previous studies; however, most patients involved received anthracycline-based chemotherapy, which has demonstrated unsatisfactory effects for ENKTL [5,33]. According to the PINK-E model, most patients are classified into the low-risk group with a 3-year OS of 81%, and only 18% of patients are classified into high-risk group with 3-year OS of 28% [6]. It is evident that an unbalanced population distribution is present in this model. In additon, the above prognostic tools are established based on AASS, which couldn't evenly distribute patients into different stages. CASS is a new staging system that can evenly distribute patients into different stages, and Lin et al. reported that CASS is superior to AASS [7]. In our study, patients classified as stages I through IV according to CASS were distributed as 56 (27.9%), 68 (33.2), 45 (21.9%), and 36 (17.6%), respectively, which was more even than the AASS. We further validated that the CASS could effectively discriminate the survival outcomes of patients who received consistent LVDP chemotherapy. The 5-year PFS and OS of patients with stages I to IV were 78.5%, 64.4%, 57.6%, and 35.7%, respectively; and 89.1%, 65.5%, 58.6%, 45.4%, respectively. The AUC of CASS was larger than that of the AASS and PINK-E in nasal-type ENKTL. Our findings further support the value of CASS as a potential staging system for nasal-type ENKTL. However, there were several limitations in our study. First, this study was a single-center retrospective and might cause selection bias. Second, the number of patients with ECOG-PS≥2 and bone marrow involvement, was relatively small and might impact the results of prognostic analysis. Third, the distributions of patients in the CTFRT group and the chemotherapy-alone group were unbalanced and might cause survival bias. Therefore, further multi-center randomized controlled trials are needed to validate our results.

Conclusion
To conclude, the LVDP combined chemotherapy regimen is effective for nasal-type ENKTL with well-tolerated toxicity, and the CASS has a better prognostic value in survival analysis with balanced patient distribution than AASS and PINK-E. Therefore, we suggest that the LVDP regimen is a promising treatment option and the CASS is a potential staging system for nasal-type ENKTL.