Neutron vs photon irradiation of inoperable salivary gland tumors: Results of an RTOG-MRC cooperative randomized study

A total of 32 patients with inoperable, recurrent or unresectable malignant salivary gland tumors were entered on a randomized RTOG/MRC study comparing fast neutron radiotherapy with conventional photon radiotherapy. Twenty-five patients were entered from the United States and 7 patients were entered from Scotland. Seventeen patients were randomized to receive neutrons and 15 patients were randomized to receive photons. Sixty-one percent of the neutron-treated patients and 75% of the photon-treated patients presented with inoperable or unresectable tumors, while 39% of the neutron-treated and 25% of the photon-treated patients had recurrent disease. Twenty-five patients were study-eligible and analyzable. The minimum follow-up time is 2 years. The complete tumor clearance rates at the primary site were 85% ( 11 13 ) for neutrons and 33% ( 4 12 ) for photons following protocol treatment ( p = 0.01). The complete tumor clearance rates in the cervical lymph nodes were 86% ( 6 7 ) for neutrons and 25% ( 1 4 ) for photons. The overall loco/regional complete tumor response rates were 85% and 33% for neutrons and photons respectively. The loco/regional control rates at 2 years for the 2 groups are 67% for neutrons and 17% for photons ( p < 0.005). The 2-year survival rates are 62% and 25% for neutrons and photons respectively ( p = 0.10). These findings are consistent with previously published uncontrolled series.