Fast neutron radiotherapy for advanced malignant salivary gland tumors.

Thirty-two patients with inoperable, recurrent, or gross residual malignant salivary gland tumors received fast neutron radiotherapy at the University of Washington. Eleven patients were treated with low energy neutrons alone, four received a combined photon-low energy neutron treatment regimen ("mixed beam"), and 17 were treated with high energy neutrons alone. Patients treated for microscopic residual tumor after a surgical resection were excluded from this study. With a minimum follow-up period of one year, (maximum 12 years), the overall locoregional tumor control rate for the entire series was 81%. The 5-year locoregional tumor control rate was 69%. The overall 5-year survival rate was 33% (50% for T3 tumors and 0% for T4 tumors). Compared to results obtained with conventional photon and/or electron treatment for advanced salivary gland tumors, fast neutron radiotherapy appears to offer a significant advantage.