Postoperative radiotherapy for oral cavity cancer with or without elective neck radiotherapy of the pN0 en bloc dissected neck: oncologic outcomes and late toxicity

Background and purpose: The benefit of elective postoperative radiotherapy (PORT) to the pN0 neck after en bloc primary tumor with neck dissection in patients with oral cavity cancer remains unclear. This nationwide multicenter retrospective observational study investigates the effect of adding or omitting elective neck irradiation to PORT of the primary tumor bed. Materials and Methods: Treatment data from 12 head and neck cancer centers in the Netherlands was pooled to compare oncologic outcomes and long-term toxicity between 2 groups of patients, i.e. in whom the PORT volume involved the primary tumor bed only (PORT-T, 118 patients) and in whom the pN0 neck was also irradiated, along with the primary tumor bed (PORT-TN, 146 patients). Results: After a median follow-up of 60 months, 5-year regional control was 96 % in both groups. The 5-year local control was 92 % vs 91 % and the 5-year overall survival was 80 % vs 78 % for the PORT-T and PORT-TN group, respectively (p-value > 0.05 for all). Multivariable analyses showed that elective irradiation of pN0 neck was significantly associated with late grade 2–3 xerostomia (OR 4,93, p < 0.01) and dysphagia (OR 5.29, p < 0.01). Conclusion: The omission of elective radiotherapy to the pN0 en bloc dissected neck in patients with oral cavity cancer resulted in comparable regional control rate to those who received elective irradiation of the neck along with the primary tumor bed with a significant reduction of late grade 2–3 radiation-related xerostomia and dysphagia. Therefore, elective irradiation of the pN0 en bloc dissected neck can safely be omitted.