Validation of nomogram-based prediction of survival probability after salvage re-irradiation of head and neck cancer.

OBJECTIVE Treatment outcomes after salvage re-irradiation in patients with recurrent head and neck cancer vary widely due to heterogeneous patient characteristics, and it is difficult to evaluate optimal re-irradiation schedules. This study aimed to validate a nomogram, originally developed by Tanvetyanon et al., used to predict the survival probability of patients with recurrent head and neck cancer after re-irradiation. METHODS Twenty-eight patients with recurrent head and neck cancer who underwent salvage re-irradiation between June 2007 and November 2011 were evaluated. The median total dose used for initial radiotherapy was 60 Gy (range, 22-72). Re-irradiation sites included the nasopharynx or Rouviere's node (n = 14), external ear (n = 4), neck lymph node (n = 3) and other sites (n = 7). Overall survival after re-irradiation was calculated using the Kaplan-Meier method, and the 2-year survival probability was estimated using Tanvetyanon's nomogram. RESULTS Twenty-two patients were treated with stereotactic body radiotherapy using a median total dose of 30 Gy (range, 15-40) in 1-7 fractions and six patients were treated with conventional external beam radiotherapy using 45 Gy (range, 23.4-60) in 10-30 fractions. The 2-year overall survival was 21.7% (95% confidence interval: 9.3-41.3), and the 2-year survival probability was 16.8% (95% confidence interval: 9.9-23.6). The 2-year overall survival in 20 patients with unfavorable prognosis (median 2-year survival probability, 5.5%) and in 8 patients with favorable prognosis (median 2-year survival probability, 45%) were 11.0 and 45.7%, respectively (P = 0.05). CONCLUSIONS Our findings show that Tanvetyanon's nomogram accurately estimates the survival probability in patients with recurrent head and neck cancer after re-irradiation.