Combined neutron-photon-therapy of locally recurrent rectosigmoidal tumors.

21 patients with unresectable recurrent adenocarcinoma of the rectum were treated with combined photon-neutron radiation therapy. 40 Gy photon were given to the whole pelvis followed by a boost field of 6.6 or 10 Gy utilizing 14 MeV monoenergetic neutrons. The latter was given with an arc therapy technique whereby the dose output fluctuations normally encountered during gantry rotation were compensated for by a computer guided system. All patients had severe pain symptoms before therapy. Twelve patients had a full remission of the symptoms and nine reported considerable relief of pain during follow-up examination. In three patients, further pain symptoms developed after six, seven, and nine months due to renewed tumor progression. In spite of the relative high neutron doses applied, side effects with the arc-technique remained minimal and did not exceed those encountered with photon therapy alone. Although the total follow-up time is relatively short at a maximum of 20 months, with a mean time of 8.5 months, the preliminary results so far are extremely optimistic leading us to further pursue the study.