A Long Survival of III-IVb Stage Nasopharyngeal Carcinoma Treated with IMRT with or without Nimotuzumab: a Propensity Score-matched Analysis

Backgrounds: To assess the efficacy of Nimotuzumab in combination with first-line treatment of chemoradiotherapy of Chinese patients with primary III-IVb stage nasopharyngeal carcinoma. Methods: Patients with primary locoregionally advanced nasopharyngeal carcinoma who were treated with intensity-modulated radiotherapy (IMRT) and concurrent Cisplatin-based chemotherapy between January, 2008 and December, 2013 at a single institution were retrospectively reviewed. Group A received at least 6 doses of Nimotuzumab; Group B did not received Nimotuzumab. A propensity score matching method was used to match patients from each group in a 1:3 ratio. Results: In total, 730 eligible patients were propensity-matched, with 184 patients in Group A and 546 in Group B. There were no significant differences in patient and tumor characteristics between Group A and Group B. At a median follow-up of 74.78 months (range 3.53–117.83 months), locoregional recurrence, distant failure and death were observed in 10.68%, 11.10% and 16.03% of all patients, respectively. Estimated 5-year locoregional relapse–free survival, distant metastasis–free survival, progression-free survival and overall survival in the Group A versus Group B were: 85.34% versus 89.79% (P=0.156), 93.09% versus 85.61% (P = 0.012), 79.96% versus 77.99% (P = 0.117) and 88.91% versus 78.30% (P=0.006), respectively. Conclusions: This nimotuzumab-containing regimen resulted in a better long-term survival in III-IVb stage NPC patients, and warrants further prospective evaluation.

in Sun Yat-sen University Cancer Centre each year. NPC is distinguished from other types of head and neck cancers due to its unique sensitivity to both radiotherapy and chemotherapy. The current management of loco-regionally advanced NPC is radiotherapy combined with cisplatin-based concurrent chemotherapy. With the development of modern radiation therapy techniques, the treatment outcomes has improved a lot during the past decades (5). However, we must realize that the treatment of NPC has entered a plateau period and need new strategy or method to improve.
EGFR is overexpressed in approximately 90% of squamous cell carcinomas of the head and neck (6)(7)(8) . More than 80% of NPC patients is also overexpressing EGFR and its expression is associated with unfavourable T stage and overall survival (9,10). With the development of molecular-targeted therapy, EGFR represents a promising therapeutic target in oncology for its correlation with aggressive phenotype, treatment resistance and poor prognosis. Nimotuzumab is a humanized anti-EGFR monoclonal antibody, which binds to the extracellular domain of the EGFR and inhibits EGF binding, designed to reduce immunoreactivity and to enhance radio sensitivity (11). Nimotuzumab has demonstrated a unique clinical safety profile (12), where anti-tumor activity was observed in absence of severe skin, renal, gastrointestinal mucosa toxicities commonly associated with EGFRtargeting antibodies (13). Previous clinical studies of nimotuzumab concurrent with radiotherapy in patients with locally advanced head and neck squamous cell carcinoma reported that the combination was well tolerated and may enhance the radio curability of unresectable head and neck neoplasms (14). In addition, the side effects of the introduce of Nimotuzumab to chemoradiotherapy were mild, and it did not affect the normal execution of radiotherapy (15).
In this study, we aimed to assess the efficacy of nimotuzumab combined with radiotherapy in patients with advanced nasopharyngeal carcinoma. The primary endpoint was the evaluation of overall survival and progression-free survival.

Patients
The Clinical Research Ethics Committee of Sun Yat-sen University Cancer Center (SYSUCC) approved this retrospective review. We reviewed the inpatient medical records of primary We performed an analysis of variance, as well as a χ 2 test, on the patients' baseline demographics and clinical characteristics. Variable differences were identified between the two groups, including gender, age, tumor stage (T stage) and node stage (N stage), clinical stage and chemotherapy regime, all of which were identified as prognostic factors for survival outcomes in a previous study. Using propensity scores to adjust for these 6 factors, we created a well-balanced cohort by matching each patient who underwent nimotuzumab with no more than three patients who underwent chemoradiotherapy without nimotuzumab (Table 1). From this stratification process, we selected a total of 730 patients comprised of 184 patients in the nimotuzumab arm and 546 patients in the no nimotuzumab arm (Table 1). We first conducted case-matched comparison between the two arms in terms of efficacy and safety in this well-balanced cohort of 730. Subsequently, we conducted univariable and multivariate analysis of those 730 patients.

Radiation Therapy
All patients received IMRT. The primary nasopharyngeal gross tumor volume (GTVnx) and ipsilateral levels IV, Vb, or supraclavicular fossae were also included for N1-3 patients).
The prescribed dose was 66-70 Gy to the planning target volume (PTV), 60 Gy to PTV1, 54 Gy to PTV2, and 60-66 Gy to PTV of the involved cervical lymph nodes in 28 to 33 fractions. All patients were treated once daily, five fractions weekly. Dose constrains to the critical structures were within the tolerance according to the RTOG 0225 protocol, and efforts were made to meet the criteria as closely as possible.

Chemotherapy
During the study period, concurrent chemoradiotherapy(CCRT) ± induction chemotherapy( IC) for stage III to IV disease was recommended according to our institutional guidelines.
The study-defined concurrent chemoradiotherapy regimen was 80-100mg/m2 cisplatin on day 1 every 3 weeks for 2-3 cycles or 30mg/m2 cisplatin weekly. Patients receiving other chemotherapy regimens or who received only one cycle of induction or concurrent chemotherapy were excluded from this study. The study-defined induction chemotherapy regimens included PF (n=161) (80-100 mg/m2 cisplatin on day 1 and 800 mg/m2 /d fluorouracil civ on days 1-5), TP (n=176)(75mg/m2 docetaxel on day 1 and 75 mg/m2 cisplatin on day 1 or TPF(142) (75mg/m2 docetaxel on day 1, 75 mg/m2 cisplatin on day 1 and 800 mg/m2 /d fluorouracil civ on days 1-5); both regimens were repeated every 3 weeks for 2-3 cycles. Reasons for deviating from the institutional guidelines included organ dysfunction suggesting intolerance to chemotherapy, patient refusal, and the discretion of the doctors in individual cases.

Nimotuzumab delivery
Nimotuzumab was not recommended for NPC patients by the guideline at that time. So the uses of Nimotuzumab was determined by the patients' willing and the experience of doctors. Intravenous Nimotuzumab was administered at an initial dose of 200mg weekly during whole radiation period. A total of 184 patients received full doses of Nimotuzumab.

Follow-up
Patient follow-up was measured from the first day of therapy to the day of last examination or death. Patients were examined at least every 3 months during the first

Statistical analysis
Distant metastasis-free survival (DMFS) and locoregional relapse-free survival (LRRFS) were calculated from day 1 after completion of treatment to first distant metastasis and locoregional relapse, respectively; progression-free survival (PFS) was calculated from day 1 after completion of treatment to locoregional relapse, distant relapse or tumor-related death, whichever occurred first. Overall survival (OS) was calculated from day 1 after completion of treatment to last examination or death respectively.
The clinic-pathologic characteristics of participants are described, and the differences of these characteristics between the Nimotuzumab group and non-Nimotuzumab group were compared by χ 2 test for categorical variables, and t-test for continuous variables. Logistic regression analysis was used to identify confounders between the treatment groups. A propensity score matching method was used. Propensity scores were calculated based on the identified potential confounders and other important factors such as tumor stage, and then each patient was assigned a score. Using 0.2-caliper width, 1:3 matching was performed between patients in the Nimotuzumab group and non-Nimotuzumab group based on the propensity scores.
LRRFS, DMFS, PFS and OS were calculated using the Kaplan-Meier method. The differences of LRRFS, DMFS, PFS and OS between two groups were tested using log-rank test.
Multivariate analysis was performed using the Cox proportional hazards models. All statistical analysis was performed using SPSS 21.0 statistical software (Chicago, IL, USA).
A p < 0.05 were considered statistically significant.

Patient characteristics
Patient characteristics are detailed in Table 1

Prognosis
The overall survival (OS) of 730 cases were analysed by univariate and multivariable cox regression models, respectively. We included sex, age, T stage, N stage, clinical stage, received nimotuzumab treatment or not and concurrent chemotherapy (with or without induction chemotherapy) in the model. The result showed that T stage , N stage, clinical stage and nimotuzumab or not were found to have prognostic significance in OS (Table 3).
Multivariate analysis indicated that N stage and nimotuzumab treatment were the independent prognostic factors for DMFS and OS

Discussion
In spite of the employment of cisplatin-based chemoradiotherapy, the treatment outcome for advanced stage is still unsatisfactory because of local recurrence and/or distant metastasis as the major pattern of disease failure (16). With modern radiation techniques and equipment, it enables to the delivery of high-dose of radiation to the target tissue while sparing normal organs at risk, thereby potentially enhancing the therapeutic efficacy (17). Previous studies have reported 90% local-regional control rates for nasopharyngeal carcinoma with the use of IMRT combined with systematic chemotherapy even in patients presenting with advanced loco-regional disease (18)(19)(20). As a consequence, distant metastasis plays an important role for the treatment failure and need to be managed properly and urgently. After decades of studies on chemotherapy for NPC, there is only slightly improve on survival and distant failure, so it is important to develop new treatment strategy to handle this issue which confuses clinical doctors for a long term.
With further research of the molecular mechanism of tumorigenesis and tumor development, molecular targeted therapy in patients with NPC has become a research hotspot. As we now know that more than 90% patients with NPC were detected for over expression of EGFR (6,7). EGFR is considered an important target in NPC treatment (21). Nimotuzumab which is a humanized anti-EGFR monoclonal antibody is obtained by replacing a murine complementary-determining region with a human framework. Nimotuzumab has shown high safety and low toxicity without severe skin and mucosa toxicities commonly associated with other EGFR targeting antibodies (12,15). As reported, compared with other EGFR inhibitors, such as Cetuximab , nimotuzumab shows a greater advantage in terms of less toxicity (22). Another advantage of nimotuzumab is that the affinity constant is quite low, allowing for high tumor uptake and low normal tissues Previous studies demonstrated that the main prognostic factors are age, gender, T, N category, clinical stage; the survival rate has been shown to decrease with the increasing T category and N category patients(27). According to our data, the multivariate analysis revealed that gender, N stage and nimotuzumab were significant prognostic factors for DMFS, N stage and nimotuzumab treatment were significant prognostic factors for OS, and node stage was a significant prognostic factor for PFS. Since only patients with clinical stage III and IV are included this study and the local-regional control rate is similar and no statistical significance (90.16% vs. 85.71%, p=0.156), this point can be explained by the use of modern radiation techniques which has been proved to improve local-regional control. While for distant failure, node stage still affects DMFS and OS as well, patients with advanced node stage have a higher chance to distant failure and lead to overall failure as a consequence. The results are consistent with other studies(5, 28). We must address that, after introduce a full course of nimotuzumab to NPC patients staged III to IV during chemoradiotherapy, there is a significant improve of overall survival with nearly 10% improve in OS significance (88.91% vs78.30%, p=0.006). The results are encouraging and beyond our expectation. The strength of nimotuzumab combined with radiotherapy in NPC may be still largely due to a strengthening of the antitumor effect that nimotuzumab and cisplatin-based chemoradiotherapy would kill tumor cells to a greater extent, which has been mentioned above.
But we must admit the limitations of this study and be cautious to interpreted the results since this study is a retrospective one. And the unavailability of the EGFR expression is another limitation since there were still a proportion of patients who were EGFR negative.
Although we eliminated selection biases, such as gender, age, T and N stages, clinical stage using propensity scores, it is unclear whether other confounding factors still exist.
In the future, some prospective, randomized, well-designed, and large sample clinical studies are needed to evaluate these indications.

Conclusions
In conclusion, our study observed that the administration of nimotuzumab to chemoradiotherapy in staged III-IV NPC patients showed promising clinic outcomes compared with chemoradiotherapy alone. However more studies, especially, prospective,

Acknowledgments
We gratefully acknowledge the staff at the clinical laboratory, Sun Yat-sen University Cancer Center for providing support to the research in this study. We also express our thanks to Xie Si-Yi and Gong Zhi-Da for data collecting.

Funding
No funding was received.

Authors' contributions
Chen

Ethics approval and consent to participate
This study complied with the standards of the Declaration of Helsinki and current ethical guidelines. It was approved by the Sun Yat-sen University Cancer Center research ethics committee. All patients provided written informed consent for the collection and publication of their medical information at the first visit to our center, which was filed in their medical records.

Consent for publication
Not applicable.   Figure 1 Study flow diagram.