Selectively sparing of the supraclavicular area during intensity-modulated radiotherapy in nasopharyngeal carcinoma: A double-center observation study

Background and purpose: This study was aimed at evaluating the feasibility of sparing the supraclavicular area, namely levels IVb and Vc, during intensity-modulated radiotherapy (IMRT) in nasopharyngeal carcinoma (NPC) patients with N1-2 disease[except N1 disease with purely restropharyngeal lymph nodes(RPN) involvement], and providing a basis for the revision of International Guideline for the delineation of the clinical target volume (CTV). Patients and materials: Patients with NPC (stage TanyN1-2M0) diagnosed pathologically in Fujian Cancer Hospital (Center 1, Only Lin SJ's attending group) from January 2014 to March 2018 and Jiangxi Cancer Hospital(Center 2) from January 2014 to December 2015 were included. According to our principle, the supraclavicular area (levels IVb and Vc) were excluded from the CTVnd. Survival outcomes focused on regional recurrence-free survival (RRFS) and recurrence rates of levels IVb and Vc were analysed. Results: A total of 672 eligible patients were recruited (Center 1, n = 362; Center 2, n = 310). There was no significant difference in 5-year RRFS (97.33 % vs. 97.24 %, p = 0.980), overall survival (OS) (89.14 % vs. 88.56 %, p = 0.327), local recurrence-free survival (LRFS) (94.90 % vs. 95.30 %, p = 0.593) and distant metastasis-free survival (DMFS) (89.38 % vs. 86.60 %, p = 0.130) between Center 1 and Center 2. Twenty patients developed regional failure (median: 36 months), among them, only one case (0.15 %) was recorded as levels IVb and Vc recurrence. Conclusion: Omitting the supraclavicular area (levels IVb and Vc) during IMRT should be safe and feasible for N12 disease (except N1 disease with purely RPN involvement). Well-designed multicenter prospective trials should be conducted to confirm our findings.