Long-term normal tissue effects of intraoperative electron radiation therapy (IOERT): late sequelae, tumor recurrence, and second malignancies.

PURPOSE: To evaluate long-term survivors treated with intraoperative electron radiation therapy (IOERT) as a component, with particular emphasis on analyzing late normal tissue toxicity, second malignancies, and patterns of delayed tumor recurrence.

METHODS AND MATERIALS: From September 1984 to December 1991, 739 patients were treated with IOERT. One hundred ninety-five patients were alive at least 5 years after IOERT (26%). Patient information regarding late complications related symptoms, incidence of second tumors, and delayed relapses were analyzed. Normal tissue changes were categorized by a modified LENT/SOMA scale (Grade 0-1, Grade 2, and Grade 3-4). Risk of late toxicity was grouped by type and number of cancer treatment modalities employed in each patient: surgery + IOERT alone (17 patients, 9%); IOERT + external radiotherapy +/- chemosensibilization (90 patients, 46%); IOERT +/- external radiotherapy +/- neoadjuvant chemotherapy (+/- previous radiotherapy) (88 patients, 45%). Biologic effective doses (BED) were calculated for alpha/beta = 3.5 for late fibrosis.

RESULTS: With a mean follow-up time of the surviving patients of 94 months (range: 55-162 months), 99 patients (51%) had Grade 0-1 toxicity, 52 (27%) had Grade 2, and 44 patients (23%) presented Grade 3-4 late normal tissue complications. Risk groups by treatment intensity did correlate with severity of observed toxicity (p < 0.001). BED estimations did not correlate with late normal tissue damage. The tumor type with higher toxicity scores was bone sarcoma (28/46, 60%), in which the estimated BED = 100.5 Gy. Peripheral neuropathy was the dominant IOERT-specific toxicity present in 24 patients (12%). Second malignancies were identified in 8 patients (4%), none inside the IOERT field (3 questionable to be marginal to the external beam radiotherapy volume). In 36 patients (18%), recurrence of the originally treated tumor was detected, including 11 (7%) local relapses.

CONCLUSIONS: The incidence of late normal tissue complications (50%) and severity (23%) is significant in a cohort of patients surviving more the 5 years after IOERT. The understanding of the contribution of IOERT to late tissue damage requires specific analysis. Peripheral neuropathy is a characteristic finding in IOERT trials. Second malignancies inside the IOERT field were not identified during the study period. The risk of recurrences, including local failures, requires an intensive follow-up of long-term survivors from IOERT trials.