CyberKnife Stereotactic Body Radiotherapy for Reirradiation of Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma: Outcomes and Prognostic Factors.

BACKGROUND

Stereotactic body radiotherapy (SBRT) is used for reirradiation in recurrent or metastatic head and neck squamous cell carcinoma (RM-HNSCC), but prognostic factors remain unclear.

METHODS

We retrospectively analyzed 36 RM-HNSCC patients treated with CyberKnife-SBRT (2009-2022).

ENDPOINTS: local control (LC) and overall survival (OS), estimated using Kaplan-Meier and Cox regression.

RESULTS

Median follow-up was 8.5 months, median OS was 9.6 months, with 1- and 2-year OS rates of 43.5% and 34.2%. One- and 2-year LC rates were 55.1% and 34.5%, with median time-to-recurrence of 14.1 months. On multivariable analysis, smoking > 30 pack-years predicted worse LC (HR 5.68; 95% CI, 1.42-22.70; p = 0.014), while former/never smoking predicted improved OS (HR 0.26; 95% CI, 0.08-0.82; p = 0.022). Gross tumor volume > 37.0 cm3 predicted worse LC (log-rank p = 0.044) and OS (p = 0.003) on univariate analysis.

CONCLUSIONS

Smoking history independently predicted LC and OS; larger tumor volume was associated with worse outcomes and may inform patient selection for SBRT reirradiation.