Risk of Severe Toxicity According to Site of Recurrence in Patients Treated With Stereotactic Body Radiation Therapy for Recurrent Head and Neck Cancer

Purpose To report a 10-year update of our institutional experience with stereotactic body radiation therapy (SBRT) for reirradiation of locally recurrent head and neck cancer, focusing on predictors of toxicity. Methods and Materials A retrospective review was performed on 291 patients treated with SBRT for recurrent, previously irradiated head and neck cancer between April 2002 and March 2013. Logistic regression analysis was performed to identify predictors of severe acute and late toxicity. Patients with <3 months of follow-up (n=43) or who died within 3 months of treatment (n=21) were excluded from late toxicity analysis. Results Median time to death or last clinical follow-up was 9.8 months among the entire cohort and 53.1 months among surviving patients. Overall, 33 patients (11.3%) experienced grade ≥3 acute toxicity and 43 (18.9%) experienced grade ≥3 late toxicity. Compared with larynx/hypopharynx, treatment of nodal recurrence was associated with a lower risk of severe acute toxicity (P=.03), with no significant differences in severe acute toxicity among other sites. Patients treated for a recurrence in the larynx/hypopharynx experienced significantly more severe late toxicity compared with those with oropharyngeal, oral cavity, base of skull/paranasal sinus, salivary gland, or nodal site of recurrence (P<.05 for all). Sixteen patients (50%) with laryngeal/hypopharyngeal recurrence experienced severe late toxicity, compared with 6-20% for other sites. Conclusions Salvage SBRT is a safe and effective option for most patients with previously irradiated head and neck cancer. However, patients treated to the larynx or hypopharynx experience significantly more late toxicity compared with others and should be carefully selected for treatment, with consideration given to patient performance status, pre-existing organ dysfunction, and goals of care. Treatment toxicity in these patients may be mitigated with more conformal plans to allow for increased sparing of adjacent normal tissues.