Unilateral vs bilateral neck irradiation: The importance of careful patient selection in tailoring radiation therapy for lateralized palatine-tonsil and non-palatine-tonsil oropharyngeal carcinoma.

TITLE: Unilateral vs Bilateral Neck Irradiation: The Importance of Careful Patient Selection in Tailoring Radiation Therapy for Lateralized Palatine-Tonsil and Non-Palatine-Tonsil Oropharyngeal Carcinoma.

PURPOSE: To compare oncologic outcomes of well-lateralized oropharyngeal carcinoma (OPC) following unilateral vs bilateral neck radiotherapy (RT).

METHODS

Patients with cT1-3 N0-2bM0 (TNM-7) OPC, treated with curative (chemo)RT in two institutions (2008-2019) were identified. For palatine tonsil tumor, unilateral neck RT was considered for tumor not invading beyond 1 cm of the tongue base or the soft palate without deep penetration. Unilateral neck RT was also considered for well-lateralized non-palatine tonsil tumor (i.e. base of tongue, soft palate or vallecula) within 1 cm of the lateral part of the mucosal corresponding oropharyngeal subsite without deep penetration. One-to-one propensity score-matched cohort of patients treated with unilateral vs bilateral neck RT was created according to patient, tumor, and treatment characteristics. The primary outcome was contralateral-only nodal failure (CNF, i.e., without local or ipsilateral regional failure). Secondary outcomes included local failure (LF), regional failure (RF), distant metastasis (DM), disease-free survival (DFS) and overall survival (OS).

RESULTS

346 patients were selected for the matched cohort (173 in each group), including 46 non-palatine tonsil tumors. The median follow-up was 5.1 years. The 5-year CNF, LF, RF, DM, DFS and OS for unilateral vs bilateral neck RT groups were 1 % (95 % CI: 0 %-3%) vs 0 %, 5 % (95 % CI: 3 %-10 %) vs 2 % (95 % CI: 0 %-5%), 4 % (95 % CI: 2 %-8%) vs 4 % (95 % CI: 2 %-8%), 5 % (95 % CI: 3 %-10 %) vs 6 % (95 % CI: 3 %-10 %), 80 % (95 % CI: 74 %-87 %) vs 79 % (95 % CI: 73 %-86 %), and 85 % (95 % CI: 80 %-91 %) vs 83 % (95 % CI: 78 %-90 %), respectively (p > 0.05 for all). One patient in the unilateral neck RT group had CNF after RT (cT2N2bM0 tonsillar cancer, successfully salvaged).

CONCLUSION

Careful selection of well-lateralized OPC to receive unilateral neck RT results in favourable oncologic outcomes.