Concurrent chemoradiotherapy with or without cetuximab for stage II to IVb nasopharyngeal carcinoma: a case–control study

Nasopharyngeal carcinoma (NPC) is an endemic carcinoma in Southern China and Southeast Asia, especially in the Guangdong province, with an annual incidence of 20–30 per 100,000 population [1‐3]. Radiotherapy (RT) is the primary treatment, and several prospective randomized trials and meta-analyses have supported the use of combined radiotherapy and chemotherapy [4‐10]. NCCN Clinical Practice Guidelines in Oncology recommended concurrent chemoradiotherapy (CCRT) with or without adjuvant chemotherapy as the standard treatment protocol for stage II–IV NPC [11].

Despite improved treatment modalities and techniques yielding excellent survival outcomes, 20%–30% of patients die of distant and/or local-regional relapse [12]. To improve this result, therapies involving molecular targets such as epidermal growth factor receptor (EGFR) have been studied extensively over the last decade. High levels of EGFR have been observed in 80% of patients with locoregionally advanced NPC and it is associated with poor clinical outcome [13]. Cetuximab, an anti-EGFR antibody, showed a survival benefit in patients with locoregionally advanced head and neck squamous cell carcinoma (HNSCC) when combined with RT [14]. In NPC, a phase II study showed that cetuximab combined with carboplatin demonstrates clinical activity for recurrent or metastatic NPC patients with previous treatment failure with platinum-based therapy [15]. The preliminary report of the ENCORE study demonstrated a promising clinical response in using cetuximab combined with CCRT in NPC [16]. A phase II study conducted by Ma et al. reported that concurrent cetuximab-cisplatin and intensity-modulated radiotherapy in locoregionally advanced NPC was feasible and preliminary survival outcomes compared favorably with historic data [17].

However, currently there are still no randomized trials that have been conducted to directly compare the outcome of CCRT alone versus concomitant cetuximab as a first-line treatment of Stage II to IVb NPC. Therefore, the purpose of this study is to compare the long-term outcome and toxicities of the NPC patients treated by CCRT with or without adding cetuximab used as a matched case-control study.

Patients diagnosed with nasopharyngeal carcinoma at our institution between January 2007 and April 2014 were identified, as a total of 7385 patients. The eligibility criteria included the following: (1) untreated, newly diagnosed NPC without distant metastasis; (2) biopsy- confirmed World Health Organization (WHO) type II-III NPC; (3) 18 ~ 70 years old; (4) without secondary malignancy, pregnancy, or lactation. Ultimately, 1971 patients were included in the study population, of them 1909 patients received CCRT alone, and only 62 patients received CCRT with cetuximab due to the expensive cost of treatment. In the 1:2 match, patients who received cetuximab plus CCRT were individually matched to two control patients receiving CCRT alone according to age, sex, pathological type, T category, N category, disease stage, RT technique, EBV DNA levels, and ECOG. The inclusion and exclusion criteria are summarized in Fig. 1.

Controversy remains regarding the additional benefit of cetuximab to concomitant chemoradiotherapy, which is the primary regimen for stage II–IV NPC. Appendix 2: Table 7. listed the related studies. Our matched case-control study aimed to clarify the feasibility and efficacy of cetuximab combined with CCRT among stage II–IV NPC patients.

Historically, the treatment of HNSCC with concurrent cetuximab and RT provides survival benefit when compared to RT alone. Bonner et al. conducted a multinational, randomized study to compare radiotherapy alone with radiotherapy plus cetuximab in the treatment of locoregionally advanced squamous-cell carcinoma of the head and neck, which found a survival advantage associated with the use of cetuximab delivered in conjunction with radiation [14]. However, a large randomized phase III trial of Radiation Therapy Oncology Group (RTOG) 0522 [23] in head and neck squamous-cell carcinoma (HNSCC), which tested whether the addition of cetuximab to cisplatin-RT were more effective, demonstrated that no discernable benefit and an increase in toxicity from adding cetuximab to radiation-cisplatin and hence should not be prescribed routinely.

In NPC, to date, studies in terms of cetuximab added to CCRT in NPC have been conducted showing that it is safe, effective, and tolerated [17, 24], while none of them was with a direct comparison of CCRT. An retrospective matched case–control study [25] on concurrent cetuximab-based bioradiotherapy (BRT) or cisplatin-based chemoradiotherapy (CRT) in patients with NPC suggested equivalence between these two treatments. In this study, the 5-year OS rates in patients in the BRT group was similar to patients treated with CRT (79.5% vs. 79.3%, P = 0.797). T. Xu et al. earlier reported a randomized phase II study [26] on patients with NPC who received concurrent cetuximab-based radiotherapy (ERT). This study demonstrated that ERT was not more efficacious than concurrent cisplatin-IMRT. In our study, we also disappointed to discover that patients in CCRT + cetuximab group achieved a 5-year OS rate similar to patients treated with re-RT+/−chemotherapy (89.7% vs. 90.7%, P = 0.386), and in PFS, LRFS, or DMFS there are also no significant improvements. Survival outcomes in this study seemed much higher than our experience [17, 24, 27] with concurrent cisplatin and radiotherapy—either with or without cetuximab. It may be due to an unbalanced distribution of disease stages in our study, in which the percentages of II, III, and IV stage patients were 8.1%, 75.8%, and 16.1%, respectively. Faced with these negative results, a plausible explanation could be that cetuximab and cisplatin have similar mechanisms of radiation sensitization [28, 29]. So tumors turned out to be resistant to both agents, and sensitive tumors would derive no additional benefit. In further study, refine study populations based on some new biologic tumor features or biomarkers, which were proved to be associated with radiation resistance or metastasis, to define patients who will benefit from cetuximab should be carefully considered.

In regard to toxicity, mucositis is the most common toxicity reported by studies regarding cetuximab combined with radiotherapy in head and neck. Notwithstanding, a pivotal trial by Bonner suggested that cetuximab did not exacerbate mucositis associated with radiotherapy of the head and neck [14]. In daily practice, though not clearly supported in the literature, the rate of mucositis with RT/CRT plus cetuximab seems higher, especially in Asians. Ethnic and lifestyle habits may play a role [30]. A randomized phase II study [26] mentioned before showed using cetuximab with RT was more likely to cause grade 3/4 oral mucositis than cisplatin-based CRT in locally advanced NPC. Ma et al. [17] also reported that using cetuximab with CCRT caused a high rate of grade 3–4 mucositis of 87% in locally advanced NPC. In this study, we found that the incidence of moderate-to-severe mucositis in the CCRT with cetuximab group was significantly higher than that in the CCRT group (51.6% vs. 23.4%, P < 0.05). The possible mechanism why cetuximab plus cisplatin add more severe oral mucositis are as followed. The epithelial cells of the oral mucosa are susceptible to the effects of cytotoxic therapy. Cisplatin can interfere with cellular mitosis and reduce the ability of the oral mucosa to regenerate [30], while cetuximab is considered to be able to enhance cytotoxic drug activity. Moreover, as patients in this study received cisplatin in two ways (triweekly and weekly), we have performed a subgroup analysis to rule out the effect of different dose schedule of cisplatin on toxicities. The finding of this stratified analysis showed that cetuximab significantly increased mucositis of NPC patients receiving CRT with triweekly cisplatin, while in weekly cisplatin delivery subgroup, the incidence of grade 3–4 mucositis in CCRT with cetuximab group and CCRT group were 30.4% and 21.7% (P = 0.403), respectively (Appendix 3: Table 8). The hematological and other non-hematological adverse events were similar between groups. Ma et al. [17] reported in a single arm retrospective study that the treatment safety was achieved when adding cetuximab to concurrent cisplatin and IMRT in locally advanced NPC. Adding cetuximab and using IMRT were the two prognostic factors predicting severe acute toxicities in this study, while earlier age and 2D–RT were the two prognostic factors predicting severe late toxicities in this study. (Appendix 4: Table 9.)

Multivariable analysis identified stage IV as an independent predictors of poor prognosis. It revealed that adding cetuximab to CCRT was not associated with a lower risk of death and disease progression than CCRT alone. Considering no survival benefit and greater toxicities, cetuximab with CCRT as the first-line treatment should be used with caution and more evidence is needed to guide the use of cetuximab in NPC.

However, there are several limitations to our study. First, the size of our study is relatively small, which might make the results of the study underpowered and selection bias might exist. Second, our study was retrospective and carried out at a single center. Although we tried to decrease potential bias by increasing the numbers in the control group, there is inevitable bias caused by its retrospective nature. Third, we did not rigorously match the delivery method of cisplatin; however, studies [31, 32] have demonstrated that radiation with concurrent cisplatin administered weekly or every 3 weeks leads to similar deliverability, toxicity profiles, and outcomes.

In conclusion, this study demonstrated that patients with stage II-IV NPC receiving CCRT with cetuximab did not achieve a benefit to survival compared to patients treated with CCRT alone, while adding cetuximab to CCRT exacerbated acute mucositis and acneiform rash. Therefore, multicenter prospective randomized clinical trials with refining study populations are warranted for further investigation.