Evaluation of planned treatment breaks during radiation therapy for anal cancer: update of RTOG 92-08.

Purpose: Radiation Therapy Oncology Group (RTOG) 92-08 began as a single arm, Phase II trial for patients with anal cancer consisting of radiation (RT) + 5-flourouracil + mitomycin-C with a mandatory 2-week break and was amended after completion to evaluate the same treatment regimen without a treatment break. Long-term efficacy and late toxicity reporting are the specific aims of this study.

Methods And Materials: Survivals were estimated with the Kaplan-Meier method. Overall survival (OS) was compared with RTOG 87-04 with the log-rank test. Time to local failure, regional failure, locoregional failure (LRF), distant metastases, second primary, and colostomy failure were estimated by the cumulative incidence method. LRF was compared with RTOG 87-04 using the Gray's test.

Results: Forty-seven patients entered in the mandatory treatment break cohort. The study was reopened in 1995 to the no mandatory treatment break cohort completing accrual with 20 patients in 1996. Of 67 total patients, 1 patient in the mandatory treatment break portion of the study did not receive any protocol treatment and is excluded from analyses. After adjusting for tumor size, neither cohort showed a statistically significant difference in OS or LRF compared with the RTOG 87-04 mitomycin-C arm. No patient in either cohort experienced a Grade 3 or higher late toxicity.

Conclusions: No statistically significant differences were seen in OS or LRF when compared to the mitomycin-C arm of RTOG 87-04, but the sample sizes for the mandatory break cohort and the no mandatory break cohort are small. Late toxicity was low and similar for the treatment cohorts.