Use of neutron therapy in the management of locally advanced nonresectable primary or recurrent rectal cancer.

Inoperable locally advanced or inoperable recurrent rectal cancer is a difficult problem. Tenesmus, discharge, bleeding and pelvic pain are frequently present and often are associated with infiltration of the sacral plexus. The value of radiotherapy in managing such patients is being appreciated, although up to 40% of the treated patients have no symptomatic response. Improvement in tumor response and control has been scored through efforts to overcome the radio resistance of the hypoxic tumor cells by neutron irradiation. This article is an account of the activity of neutron radiotherapy in such patients. Over 350 patients were entered in studies comparing neutrons used alone and neutrons used in a mixed-beam treatment schedule. At present no therapeutic gain for long-lasting survival has been achieved; however, local control and pain improvement seems to be better with neutrons than with photons.