The effects of carbon ion irradiation revealed by excised perforated intestines as a late morbidity for uterine cancer treatment

Purpose. Clinical trials of carbon ion therapy have been performed due to the advantages of high-dose energy delivery with precise localization control to targeted organs and strong cell-killing activities to cancers. Perforated intestines as a late morbidity after carbon ion radiotherapy for uterine cancers were examined to reveal the biological characteristics of carbon ion for future applications for the treatment of gastrointestinal cancers. Methods. Between June 1995 and December 2004, 94 patients with carcinoma of the uterine cervix or corpus were treated with carbon ion therapy. Among them, 9 patients (9.6%) developed major late gastrointestinal (GI) complications. Four out of 9 patients had intestinal perforations excised operatively at our institute. The postoperative clinical courses and histopathological findings of the excised intestine were investigated. Results. Carbon ion irradiation severely damaged smooth muscle layers by coagulation necrosis as well as atrophy of the intestinal epithelium and middle-sized arterial thromboses of the intestines. After evaluating late complications, the dose constraints on the GI tracts were set under 60 GyE to prevent major complications. Thereafter, the incidence of major GI complications markedly decreased. Conclusion. Our findings demonstrated the characteristic histopathological effects of carbon ion radiotherapy and thus are expected to facilitate future additional applications of carbon ion radiotherapy for the treatment of gastrointestinal cancers.