Acute treatment-related diarrhea during postoperative adjuvant therapy for high-risk rectal carcinoma

The combination of pelvic radiotherapy and 5-fluorouracil-based chemotherapy is associated with an increase in acute gastrointestinal toxicity during rectal adjuvant therapy, most notably an increased incidence of diarrhea. Previous randomized, prospective studies have limited their analysis to presenting rates of severe and life-threatening diarrhea (Grade 3 or greater), and few data are available detailing the extent of mild to moderate diarrhea. To provide baseline data for future studies, we conducted a detailed analysis of diarrhea from a prior clinical trial of adjuvant therapy for rectal cancer.

In a multiinstitutional clinical trial, 204 eligible patients with rectal carcinoma that either was deeply invasive (T3-T4) or involved regional lymph nodes were randomized to receive either postoperative pelvic radiotherapy alone (45 to 50.4 Gy) or pelvic radiotherapy and bolus 5-fluorouracil-based chemotherapy. Toxicity was assessed prospectively.

For the 99 eligible patients who received pelvic radiotherapy alone, rates of Grades 0, 1, 2, 3, and 4 diarrhea during treatment were 59, 20, 17, 4, and 0%, respectively. For the 96 eligible patients who received radiotherapy and 5-fluorouracil, the overall rates of grades 0, 1, 2, 3, and 4 diarrhea were 21, 34, 23, 20, and 2%, respectively. The increased rates of diarrhea during adjuvant rectal therapy were manifested across all toxicity levels for patients receiving chemotherapy and pelvic radiotherapy. Of primary clinical importance is the substantial increase in severe or life-threatening diarrhea (Grade 3 or more) (22 vs. 4%,p = 0.001) Additionally, increased rates of any diarrhea and also severe or life-threatening diarrhea were observed in patients who had a low anterior resection compared with those who had an abdominoperineal resection (p < 0.001 and p = 0.006, respectively).

These results will be of value as a baseline for investigators who want to use treatment toxicity as an end point in cancer control or cancer therapy trials utilizing similar treatment techniques. Patients receiving 5-fluorouracil and pelvic radiotherapy compared with patients receiving pelvic radiotherapy alone and patients with a prior history of a low anterior resection compared with patients who had a prior history of an abdominoperineal resection experienced increased rates of Grades 1 through 4 acute treatment-related diarrhea, and the most important increase occurred as Grade 3 toxicity.