Intraoperative electron beam radiotherapy in recurrent colorectal carcinoma

The installation of a dedicated linear accelerator in a shielded operating room in 1992 allowed us to start a feasibility study of intraoperative electron beam radiation therapy (IOERT) in colorectal carcinoma.

From March 1992 to February 1996, 28 patients with recurrent colorectal carcinoma were treated with maximal surgical resection and IOERT to the pelvis (n = 20) or paraortics (n = 8). IOERT dose ranged from 10 to 20 Gy with electron energies of 6-15 MeV. Postoperative external beam radiation therapy (EBRT) of 45-50 Gy was planned for the previously unirradiated patients.

IOERT was well tolerated, but 10 (70%) of 13 patients in the previously unirradiated group did not complete the EBRT per protocol. Eight patients (29%) had some morbidity including surgically related fistula distal from IOERT sites. Two patients developed pelvic pain, which can be attributed to IOERT. Three-year local control at sites treated with IOERT was 40% (53% for previously irradiated patients and 27% for previously unirradiated patients). The 3-year actuarial overall survival was 12% (17% for previously irradiated patients and 8% for previously unirradiated patients).

Our initial experience showed that it was feasible to treat poor prognostic colorectal cancer patients with IOERT. The morbidity observed was mainly related to extensive surgery in high-risk patients. Poor local control was obtained in patients treated with low-dose IOERT alone. Hence, previously unirradiated patients are encouraged to complete the planned EBRT or, alternatively, are considered for EBRT preoperatively or are given a higher IOERT dose (up to 20 Gy) if EBRT will not be given. Since IORT doses >20 Gy are associated with nerve toxicity, we currently add limited dose EBRT in the previously irradiated group. Patients with disease located in multiple abdominal sites are no longer considered candidates for IOERT.