A tumor/normal tissue advantage for low dose rate neutron brachytherapy.

Reports on clinical study of Cf-252 pelvic brachytherapy are reviewed and show that complication frequency is low. Low dose rate (LDR) neutron brachytherapy has been shown to be effective against cervical and advanced pelvic cancers; and produces 5 year cures without a high frequency of normal tissue complications. This is attributed to a high relative biological effectiveness (RBE) for the bulky, hypoxic tumor which along with an oxygen enhancement ratio (OER) advantage and dose-rate independent effects, produces rapid tumor regression and good local tumor control. Adjacent normal tissues which are oxygenated have lower RBE values than that of hypoxic tumors. Cf-252 brachytherapy increases the dose differential, therapeutic gain and the probability of local tumor control, since the high RBE of Cf-252 for hypoxic tumor is much less in normal tissues. Cf-252 radiation concentrated in the tumor, and for this reason, has had much fewer attendant normal tissue complications compared to neutron beam therapy.