Radiation therapy quality control in a clinical trial of adjuvant postoperative treatment for rectal cancer

Purpose: Deviations from protocol can detract from the reliability of results obtained in prospective clinical trials. In an effort to decrease the number of deviations in a prospective trial of adjuvant treatment for rectal cancer, we undertook pretreatment review of the irradiated fields. Methods and Materials: Before initiation of radiation therapy, patients' radiation therapy fields were simulated by their radiation oncologists and films were submitted for review. The treating physicians were then informed whether their fields were in compliance with the protocol or whether any modifications were needed. Results: Among the 625 patients participating in this study who received radiation therapy as a component of protocol treatment, 419 (67%) had no radiation therapy deviations, 127 (20%) had minor deviations, and 51 (8%) had major deviations; 28 (4%) could not be evaluated or did not receive protocol treatment because of circumstances eyond the treating radiation oncologist's control. The pretreatment quality control review identified major deviations in the radiation portals for 57 cases; these findings were communicated to the radiation oncologists prior to initiation of treatment, and, on final review, 40 had no deviation or only minor deviation. Conclusion: In the absence of pretreatment quality control review, 40 additional patients would have had major deviations from their radiation therapy protocol. On the basis of these findings, it is estimated that pretreatment quality control reduced the rate of major deviation from 15% to 8%. Pretreatment review of radiation therapy parameters is an effective method of reducing the frequency of major deviations in prospective clinical trials.