Promising clinical outcomes of sequential and "Sandwich" chemotherapy and extended involved-field intensity-modulated radiotherapy in patients with stage IE /IIE extranodal natural killer/T-cell lymphoma.

BACKGROUND
The optimal treatment for the rare subtype of non-Hodgkin lymphoma, extranodal natural killer/T-cell lymphoma (ENKTL), nasal-type, has not been clearly defined. The purpose of the study was to investigate the efficacy of sequential and "Sandwich" chemotherapy and extended involved-field intensity-modulated radiotherapy (IMRT) in patients with stage IE /IIE extranodal ENKTL, nasal-type.


METHODS
One hundred and fifty-five patients with stage IE /IIE nasal-type ENKTL were enrolled in the study, including 99 patients treated with sequential chemotherapy and extended involved-field IMRT (SCRT) and 56 patients with "Sandwich" chemotherapy and extended involved-field IMRT and chemotherapy (SCRCT). All patients were treated with extended involved-field IMRT with median dose of 54.6 Gy to the primary tumor and positive lymph nodes. Ninety-four patients had Ann Arbor stage IE disease, and 61 patients had stage IIE disease.


RESULTS
The 5-year rates of loco-regional recurrence (LRR), progression-free survival (PFS), and overall survival (OS) were 17.0%, 78.5%, and 84.7%, respectively. Univariate analysis revealed that EBV DNA copy after treatment (normal vs elevated level) was significant prognostic factor for LRR, PFS, and OS (P < 0.001); therapeutic method (SCRT vs SCRCT) was significant prognostic factor for PFS (71.0% vs 91.8%, P = 0.011), but there was no significant effect on 5-year LRR and OS (22.2% vs 8.2%, P = 0.051 for LRR; 80.9% vs 91.8%, P = 0.199 for OS).


CONCLUSIONS
Compared with SCRT, SCRCT was significantly associated with higher PFS rates and showed a trend toward improved loco-regional control. EBV DNA copy after treatment is a good index for recurrence and prognosis for stage IE /IIE ENKTL patients.


| INTRODUCTION
Extranodal natural killer/T-cell lymphoma (ENKTL), nasal-type, is a distinct subtype of non-Hodgkin lymphoma (NHL) that is common in Asia but rare in Europe and North America. [1][2][3][4][5][6] The upper aerodigestive tract is the most commonly involved site, 3,7 particularly the nasal cavity and Waldeyer's ring. Because of the rarity of ENKTL worldwide and its heterogeneity, optimal treatment strategies have not been defined to date.
Previous studies have shown that ENKTL is sensitive to radiotherapy, [8][9][10][11][12][13][14][15] but resistant to conventional chemotherapy due to the overexpression of the multidrug-resistant P-glycoprotein. 16,17 After treatment with concurrent chemoradiotherapy (CCRT), Kim et al 18 reported 3-year progression-free survival (PFS) and overall survival (OS) as high as 85.19% and 86.28%, respectively, in patients with stage I E /II E . Another prospective research study, 19 which adopted CCRT, reported a 5-year OS of 70% for localized nasal natural killer/T-cell lymphoma. However, the previous two studies adopted three-dimensional conformal radiotherapy (3D-CRT); currently, with the rapid development of radiotherapy technology, IMRT has been widely applied in clinical work as it is more precise and provides better dose coverage. 20,21 This aim of this study was to explore the clinical outcomes in early-stage ENKTL patients treated with sequential (chemotherapy-IMRT, SCRT) or "Sandwich" (chemotherapy-IMRT-chemotherapy, SCRCT) chemoradiotherapy.

| Patient eligibility criteria
One hundred and fifty-five patients with stage I E or II E ENKTL who received sequential (SCRT) or "Sandwich" (SCRCT) chemotherapy and extended involved-field IMRT consecutively in Sun Yat-Sen University Cancer Center between January 2010 and August 2015 were recruited in this study. The sites of primary tumor were located within the nasal cavity (n = 120) or Waldeyer's ring (n = 32), and the other sites of upper aerodigestive tract (n = 3). The diagnostic criteria were based on the 2008 WHO classification of Tumours of Haematopoietic and Lymphoid Tissues, and every case was diagnosed after a consensus was reached among at least two experts.
The majority of patients who showed the pathologic features of angiocentricity zone necrosis and polymorphism of individual cells and tumor cells also expressed NK/T-cell markers, such as CD2,CD3ε(+), cytotoxic granule proteins (TIA-1, granzyme-B, and perforin), CD56, and EBV encoded small RNA in situ hybridization, but they did not express Bcell markers such as CD20 and/or CD79α.
Patients were staged according to the Ann Arbor staging system. Clinical evaluation of patients included history and physical examination, contrast-enhanced magnetic resonance imaging (MRI) of the head and neck, complete blood count, liver and renal function tests, serum lactate dehydrogenase levels (LDH), contrast-enhanced CT of the chest and abdomen/pelvis, bone marrow aspiration and/or biopsy. Positron emission tomography/computed tomography (PET/CT) was performed in 97 patients.

| Treatment
Ninety-nine patients received sequential chemotherapy and extended involved-field IMRT (SCRT) and 56 patients received "Sandwich" chemotherapy followed by extended involved-field IMRT and chemotherapy (SCRCT).
RT was delivered using extended involved-field IMRT with 6-MV photon beams, and all plans were calculated using the Eclipse or Monaco system. The median radiation doses were 54.6 Gy (46.0-60.9 Gy) for primary tumor or positive lymph nodes, 50.7 Gy (46.0-56.0 Gy) for high-risk clinical target volume (CTV1), and 45.5 Gy (36.0-52 Gy) for low-risk clinical target volume (CTV2). Gross tumor volume (GTV) was defined as the gross tumor extent shown on the imaging studies and physical examination before treatment, including the primary tumor and involved regional lymph nodes. High-risk clinical target volume (CTV1) included GTV and adjacent structures in risk, such as nasal mucosa, nasopharyngeal mucosa, the retropharyngeal lymph nodes, the Waldeyer's ring, and ethmoid sinus. The low-risk clinical target volume (CTV2) included the corresponding neck lymphatic drainage area, such as the upper cervical lymph node was included when nasopharynx or retropharyngeal lymph node was involved and the whole cervical lymph node was included when an upper cervical lymph node was involved.

Prognostic factor
No.

| Statistical analysis
The primary endpoint was loco-regional recurrence (LRR), and the secondary endpoints were progression-free survival (PFS) and overall survival (OS). The response was evaluated based on the International Workshop Criteria reported in 1999. 22 LRR was defined as a relapse at the primary tumor site, adjacent organ/structure, or regional lymphoma nodes. Complete remission (CR) was defined as a complete regression of all visible/palpable tumors and radiographic disease. OS was measured from the start of initial treatment until time of death from any causes or until last follow-up. PFS was measured from the start of initial treatment until time of first local or distant progression or relapse, or until last follow-up, or death. A survival curve was constructed using the Kaplan-Meier method, and the groups were compared using the log-rank test. A P value < 0.05 was considered statistically significant. All statistical analyses were performed using IBM SPSS Statistics, version 22.0 (IBM Corp., Armonk, NY, USA).

| Patient characteristics
The clinical features of all 155 patients are summarized in Table 1.

| Treatment response
When all patients completed chemotherapy and extended involved-field IMRT, 144 patients were assessable for a response, including 124 cases (86.1%) who achieved CR and 16 cases who achieved PR, one patient had SD and three patients had PD.

F I G U R E 1
Kaplan-Meier survival curves for all patients in this study. The 5-y loco-regional recurrence (LRR) rate for all patients is 17.0% (A). The 5-y progression-free survival (PFS) rate for all patients is 78.5% (B

| Survival and prognostic factors
The median follow-up time for survival was 44.5 months (range 3.8-84.1 months). The 5-year LRR, PFS, and OS rates for all patients were 17.0%, 78.5%, and 84.7%, respectively ( Figure 1). Patients' characteristics were evaluated for prognostic significance against LRR, PFS, and OS (Table 1). According to univariate analysis results, the following variables were associated with the 5-year OS rate: EBV DNA copy after treatment (normal vs elevated level, P < 0.001) and response after treatment (CR vs no-CR, P = 0.019). Elevated EBV DNA copy after treatment (normal vs elevated level, P < 0.001) and therapeutic method (SCRT vs SCRCT, P = 0.011) were found to be significant prognostic factors for 5-year PFS. Elevated EBV DNA copy after treatment (P < 0.001) was found to be significant prognostic factors for 5-year LRR, and therapeutic method (SCRT vs SCRCT, P = 0.051) showed a trend toward improved loco-regional control ( Table 2).

| Toxicities
Data on toxicities are summarized in Table 3. No patient developed Grade 3 or 4 toxicity. The most frequent toxicity was mucositis. In SCRT group, mucositis was scored as Grade 1 in 51 patients (51.5%) and Grade 2 in 19 patients (19.2%). In SCRCT group, mucositis was scored as Grade 1 in 32 patients (57.1%) and Grade 2 in 12 patients (21.4%).

| DISCUSSION
The main finding of this study is that, compared with SCRT, SCRCT was significantly associated with higher PFS rates and showed a trend toward improved loco-regional control (PFS: 71.0% vs 91.8%, P = 0.011; LRR: 22.2% vs 8.2%, P = 0.051). Another valuable finding is that EBV DNA copy after treatment is significantly associated with 5-year LRR, PFS, and OS.
In order to improve the local and systemic disease control for ENKTL patients, Yamaguchi et al 19,23 performed the first prospective trial of CCRT involving 27 patients with localized nasal NKTCL treated with concurrent 3D-CRT (50 Gy) and three cycles of DeVIC. They showed a 5-year OS of 70% and PFS of 63%. Kim et al 18 enrolled 30 stage I E /II E nasal ENKTL patients who received CCRT (3D-CRT radiation, 40-52.8 Gy and cisplatin, 30 mg/m 2 weekly) followed by three cycles of VIPD resulting in 3-year PFS and OS rates of 85.19% and 86.28%, respectively. The two studies achieved satisfactory outcomes by CCRT; however, in the two studies, 3D-CRT radiation was adopted as RT. In contrast, IMRT is now widely used in clinical practice as it can achieve superior target coverage and dose conformity compared with 3D-CRT and provides equivalent or slightly better organs at risk (OARs) avoidance compared with 3D-CRT. 20,21 This study also achieved excellent LRC and favorable prognoses for patients with stage I E /II E ENKTL compared with the two CCRT studies. 20,21 Our favorable clinical results are likely due to IMRT adopted in all patients. IMRT

F I G U R E 2
The comparison of loco-regional recurrence (LRR), progression-free survival (PFS), and overall survival (OS) rates between patients in two groups with two different treatment modes (Group A: 99 patients who were treated with sequential chemotherapy and extended involved-field IMRT [SCRT]; Group B: 56 patients who were treated with "Sandwich" chemotherapy and extended involved-field IMRT and chemotherapy [SCRCT]). The 5-y LRR of patients in group A and group B are 22.2% vs 8.2% (P = 0.051), respectively (D). The 5-y PFS of patients in group A and group B is 71.0% vs 91.8%, respectively (P = 0.011) (E). The 5-y OS of patients in group A and group B are 80.9% vs 91.8%, respectively (P = 0.199) (F) was been proven to achieve excellent target coverage and dose conformity, as well as favorable prognosis and LRC rates with acceptable toxicities in patients with nasal and Waldeyer's ring NKTCL (WR-NKTCL). 24,25 Wang et al 25 analyzed 42 patients with early-stage nasal NK/T-cell lymphoma who received high-dose (ie, median radiation dose to the primary tumor of 50 Gy) and extended involvedfield IMRT with or without combination chemotherapy and reported 2-year LRC, OS, and PFS rates of 93%, 78%, and 74%, respectively. Similarly, Bi et al 24 retrospectively reviewed 30 patients with early-stage WR-NKTCL who received high-dose (ie, 50 Gy to the primary involved regions and positive cervical lymph nodes and 40 Gy to the negative cervical nodes) and extended-field IMRT and reported 2-year OS, PFS, and LRC rates of 71.2%, 57.4%, and 87.8%, respectively.
Another possible reason for our success may be related to the fact that the majority of patients in this study received GELOX or GELOX-like chemotherapy regimens, which is not affected by P-glycoprotein and produces a better prognosis with less toxicity than EPOCH /CHOP in early-stage ENKTL patients. [26][27][28] Previous studies have shown that CHOP or CHOP-like regimens lead to inferior treatment outcomes. Wang et al 28 reported the 2-year OS and PFS were both 86% for stage I E /II E ENKTL patients treated with GELOX followed by involved-field radiation.
In this study, mucositis and xerostomia are the most common radiotherapy-related toxicities, but no patient developed Grade 3 or 4 toxicities were documented. The reason for the mild radiotherapy-related toxicities is that all patients were treated with IMRT, which had been proven to well protect OARs, such as parotid gland. Compared with SCRT group, patients in SCRCT group were more frequently to develop hematologic toxicities, such as leukopenia, anemia, and thrombocytopenia, and this may be the results of the more cycles of chemotherapy in SCRCT group.
In conclusion, sequential and "Sandwich" chemotherapy (GELOX-based) combined with extended involved-field IMRT could get ideal clinical outcome. Compared with SCRT, SCRCT could get higher PFS rates and show a trend toward improved loco-regional control. EBV DNA copy after treatment is a good index for recurrence and prognosis for stage I E /II E ENKTL patients.