Stereotactic Reirradiation in the Treatment of Head and Neck Cancers: A Retrospective Study on the Long-Term Experience of the Oscar Lambret Center.

Background and purpose: Stereotactic radiotherapy potentially treats unresectable recurrences of previously irradiated head and neck (H&N) cancer. This study aimed to assess its efficacy and safety and evaluate prognostic factors.Materials and methods: We conducted a large retrospective series that included 110 patients who had undergone 36-Gy, six-fraction stereotactic reirradiation (CyberKnife (R)) for recurrent/secondary H&N cancer between 2007 and 2020 at the Oscar Lambret Center. Patient characteristics and toxicities were assessed. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method.Results: Median follow-up time was 106.3 months. The 2-year OS rate was 43.8 % (95 % confidence interval, 95 % CI, 34.3-52.9) and the median survival was 20.8 months (95 % CI, 16.5-26.3). The cumulative 2-year localrecurrence, regional-recurrence, and distant-metastasis rates were 52.2 % (95 % CI, 42.4-61.1 %), 12.8 % (95 % CI, 7.4-19.8 %), and 11 % (95 % CI, 6.0-17.6 %), respectively. 73 patients received concomitant cetuximab, and it was not significantly beneficial (HR = 1.34; 95 % CI, 0.80-2.26; p = 0.26). The cumulative incidences of grade >= 2 late toxicity was 42 % (CI95%: 33-51) at 24 months. Two grade 4 bleedings and no treatment-related deaths were reported.Conclusion: In a large retrospective series of SBRT reirradiation for recurrent or second primary H&N cancers, we observed a median OS of 20.8 months, with a cumulative incidence of grade >= 2 late toxicity of 42 % at 24 months. Such a treatment is feasible. However, local recurrence rates remain non-negligible, warranting further research. Radiosensitizer use is currently under study. Therefore, establishing a balance between therapeutic modifications and toxicity is essential.