Predictive value of skin invasion in recurrent head and neck cancer patients treated by hypofractionated stereotactic re-irradiation using a cyberknife

Background This study aimed to elucidate the influence of skin invasion in patients with recurrent head and neck cancer treated with re-irradiation using stereotactic radiotherapy. Materials We reviewed 104 patients treated using CyberKnife in four institutions. Results Nine cases of skin invasion were recognized (8.6 %). Larger tumors tended to exhibit skin invasion. The skin invasion (+) group showed a lower response rate (0/9, 0 %) than the skin invasion (−) group (56/95, 59 %) (p = 0.002). The skin invasion (+) group showed lower local control (LC) and progression free survival (PFS) rates, both 0 % at 6 months, than the skin invasion (−) group, which had a LC of 69 % (p = 0.0001) and a PFS of 48 % at 1 year (p = 0.0157). Median survival time and one-year survival rates for the skin invasion (+) and (−) groups were 6.6 vs. 15.3 months and 14 % vs. 59 % (p = 0.0005), respectively. No patient with skin invasion survived more than 14.4 months. The percentage of patients who developed grade 3 or higher toxicity was 44 % in the skin invasion (+) group and 18 % in the skin invasion (−) group (p = 0.14). Conclusions Skin invasion is an important predictor of poor prognosis in recurrent head and neck cancer after re-irradiation with stereotactic radiation therapy.