Comparison of the Clinical Outcomes of Patients with Squamous Cell Carcinoma of the Tonsil Receiving Postoperative Ipsilateral Versus Bilateral Neck Radiotherapy: A Propensity Score Matching Analysis (KROG 11-07)

Purpose The impact of postoperative ipsilateral neck radiotherapy (INRT) versus bilateral neck radiotherapy (BNRT) on the clinical outcomes of patients with tonsillar squamous cell carcinoma was analyzed retrospectively. Materials and Methods Between October 2001 and June 2012, 241 patients with T1-2 and N0-N2b tonsillar carcinoma from 16 institutes underwent postoperative INRT (n=84) or BNRT (n=157) following a tonsillectomy. Seventy patients were identified from each group by propensity score matching and compared in terms of the overall survival (OS), disease-free survival (DFS), locoregional relapse-free survival (LRRFS), and distant metastasis-free survival (DMFS) rates calculated using the Kaplan-Meier method with a log-rank test. Results The median follow-up was 55 months (range, 3 to 133 months). The survival outcomes in the INRT and BNRT groups were similar: 5-year OS (92.8% vs. 94.0%, p=0.985), DFS (80.5% vs. 94.2%. p=0.085), LRRFS (88.1% vs. 97.1%, p=0.083), and DMFS (92.7% vs. 97.0%, p=0.370). Subgroup analysis revealed no contralateral neck recurrence in 61 patients with T1-2N0-2a regardless of the treatment groups. For 79 patients with N2b, contralateral neck recurrence was more common in the INRT group than in the BNRT group (7.9% vs. 0.0%), but the difference was not significant (p=0.107). The overall grade ≥ 2 toxicities were lower in the INRT group: acute (45.7% vs. 74.3%, p=0.001) and late (4.3% vs. 31.4%, p < 0.001), respectively. Conclusion INRT is an attractive strategy for patients with T1-2N0-2a tonsillar carcinoma compared to BNRT. For patients with N2b, there was a small risk of contralateral neck recurrence when treated with INRT, but its impact on the OS was limited with successful salvage treatment. Key words: Ipsilateral neck, Adjuvant radiotherapy, Tonsillar neoplasms, Radiation volume, Toxicity