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

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). 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. 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). 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.