Benefit from adjuvant radiotherapy in early-stage oral cavity and oropharyngeal cancer with solitary ipsilateral lymph node metastasis – A population-based study on German cancer registry data

BACKGROUND: The benefit of adjuvant radiotherapy (RT) for patients with early-stage oral cavity squamous cell carcinoma (OSCC) or p16-negative oropharyngeal squamous cell carcinoma (OPSCC) with a solitary ipsilateral lymph node metastasis remains unclear. METHODS: A population-based analysis was conducted to assess overall survival (OS) and the incidence of locoregional recurrence (LRR) in patients diagnosed with pT1/pT2 OSCC or p16-negative OPSCC and a solitary ipsilateral lymph node metastasis without extracapsular spread (pN1) between 2017 and 2022. Information regarding clinical characteristics and outcomes was gathered from 12 clinical cancer registries in January 2024. The data were compared between those patients who underwent surgical resection alone and those who had surgery followed by adjuvant RT. RESULTS: The final analysis included 526 patients, with 250 individuals receiving treatment for OSCC and 276 for p16-negative OPSCC. Of these, 230 patients (43.7 %) underwent surgical resection, and 296 (56.3 %) had surgery followed by adjuvant RT. The addition of adjuvant RT was associated with improved 5-year OS (p = 0.0079) and reduced LRR incidence (p = 0.0013). In multivariate Cox regression analysis, adjuvant RT was associated with improved OS (HR 0.49 [0.32; 0.76]) and a reduced risk of LRR (HR 0.39 [0.22; 0.69]). CONCLUSION: This clinical cancer registry study portends an oncological benefit of adjuvant RT for patients with early-stage (pT1/pT2) OSCC and p16-negative OPSCC who present with solitary ipsilateral lymph node metastasis. This benefit was particularly notable in the sub-cohort of younger patients with p16-negative OPSCC and the sub-cohort of elderly patients with OSCC.