Preoperative radiation with concurrent chemotherapy for resectable rectal cancer: effect of dose escalation on pathologic complete response, local recurrence-free survival, disease-free survival, and overall survival

Abstract

Purpose: Three Phase II studies of preoperative radiotherapy and concurrent 5FU chemotherapy were undertaken. The primary endpoints were acute toxicity and pathologic complete response rate (pCR). Secondary endpoints were local recurrence-free survival (LRFS), disease-free survival (DFS), and overall survival (OS).

Methods and materials: A total of 134 patients with adenocarcinoma of the rectum (clinical T3/T4 or N1/N2) were treated. The initial cohort received 40 Gy in 20 fractions, the second 46 Gy in 23 fractions, and the third 50 Gy in 25 fractions. 5FU (225 mg/m2/day) was given continuously throughout radiotherapy. A total of 121 patients underwent surgical resection.

Results: Treatment was well tolerated. Grade 3/4 acute toxicity was observed in 13%, 4%, and 14% of patients in the 40 Gy, 46 Gy, and 50 Gy cohorts, respectively (p = 0.20). pCR was documented in 15%, 23%, and 33% of patients, respectively (p = 0.07). The 2-year actuarial LRFS was 72%, 90%, and 89% (p = 0.02); DFS was 62%, 84%, and 78% (p = 0.02); and OS was 72%, 94%, and 92%, respectively (p = 0.03).

Conclusions: All treatment schedules were well tolerated. There was a trend toward increased pCR with higher doses. A statistically significant increase in LRFS, DFS, and OS was seen with radiation doses of 46 Gy and greater, but there was no difference between 46 Gy and 50 Gy.