Boron neutron capture therapy for locally recurrent head and neck squamous cell carcinoma: An analysis of dose response and survival

BACKGROUND AND PURPOSE: Head and neck squamous cell carcinoma (HNSCC) that recurs locally is a therapeutic challenge. We investigated the efficacy of boron neutron capture therapy (BNCT) in the treatment of such patients and the factors associated with treatment response and survival. METHODS AND MATERIALS: Seventy-nine patients with inoperable, locally recurred HNSCC were treated with l-boronophenylalanine-mediated BNCT in Espoo, Finland, between February, 2003 and January, 2012. Prior treatments consisted of surgery and conventionally fractionated radiotherapy to a median cumulative dose of 66 Gy (interquartile range [IQR], 59-70 Gy) administered with or without concomitant chemotherapy. Tumor response was assessed using the RECISTv.1.0 criteria. RESULTS: Forty patients received BNCT once (on 1 day), and 39 twice. The median time between the 2 treatments was 6 weeks. Forty-seven (68%; 95% confidence interval [CI], 57-79%) of the 69 evaluable patients responded; 25 (36%) had a complete response, 22 (32%) a partial response, 17 (25%) a stable disease lasting for a median of 4.2 months, and 5 (7%) progressed. The patients treated with BNCT twice responded more often than those treated once. The median follow-up time after BNCT was 7.8 years. The 2-year locoregional progression-free survival rate was 38% and the overall survival rate 21%. A high minimum tumor dose and a small volume were independently associated with long survival in a multivariable analysis. CONCLUSIONS: Most patients responded to BNCT. A high minimum tumor dose from BNCT was predictive for response and survival.