Combination chemotherapy versus single-agent chemotherapy during preoperative chemoradiation for resectable rectal cancer

Heloisa M Resende, Luiz Felipe Pitzer Jacob, Luciano Vasconcellos Quinellato, Delcio Matos, Edina MK da Silva

Colorectal cancer represents 10% of all cancers and is the third most common cause of death in women and men. Almost two-thirds of all bowel cancers are cancers of the colon and over one-third (34%) are cancers of the rectum, including the anus. Surgery is the cornerstone for curative treatment of rectal cancer. Mesorectal excision decreases the rate of local recurrences; however, it does not improve the overall survival of people with locally advanced rectal cancer. There have been significant research efforts since the mid-1990s to optimise the treatment of rectal cancer. Based on the findings of clinical trials, people with T3/T4 or N+ rectal tumours are now being treated preoperatively with radiation and chemotherapy, mainly fluoropyrimidine. However, the incidence of distant metastases remains as high as 30%. Combination chemotherapy regimens, similar to those used in metastatic disease with the addition of oxaliplatin and irinotecan, have been tested to improve the prognosis of people with rectal cancer. To compare outcomes (including overall survival, disease-free survival and toxicity) between two 5-fluorouracil-containing chemotherapy regimens in people with stage II and III rectal cancer who are receiving preoperative chemoradiation. We searched the Cochrane Colorectal Cancer Group Specialised Register (January 2015), the Cochrane Central Register of Controlled Trials (2015, Issue 1), Ovid MEDLINE (1950 to January 2015), Ovid EMBASE (1974 to January 2015) and LILACS (1982 to January 2015). We reviewed the reference lists of included studies, checked clinical trials registers and handsearched relevant journal proceedings. We applied no language or publication restrictions. Randomised controlled trials (RCTs) comparing single-agent chemotherapy (fluoropyrimidine) versus combination chemotherapy (fluoropyrimidine plus another agent including, but not limited to, oxaliplatin) during preoperative radiochemotherapy in people with resectable rectal cancer. Two review authors (HMR, EMKS) independently extracted data and assessed trial quality. When necessary, we requested additional information and clarification of published data from the authors of individual trials. We included four RCTs involving 3875 people with resectable rectal cancer. In the preoperative period, the participants of these studies were randomised to receive chemoradiation either with a single fluoropyrimidine agent (capecitabine or 5-fluorouracil) or with a combination of drugs (fluoropyrimidine plus oxaliplatin). The only study that reported overall survival and disease-free survival found no significant differences between the intervention and control groups; we considered this evidence very low quality.For pathological complete response after preoperative treatment (ypCR) there was high quality evidence favouring the intervention group (odds ratio (OR) 1.19, 95% confidence interval (CI) 1.03 to 1.37), but there was also moderate quality evidence suggesting a higher risk for early toxicity in the intervention group (OR 2.07, 95% CI 1.31 to 3.27). Moderate to high quality evidence suggested that the control group had better compliance to radiotherapy (OR 0.32, 95% CI 0.14 to 0.75). There were no significant differences between groups in postoperative mortality within 60 days, postoperative morbidity, resection margins, abdominoperineal resection and Hartmann procedures. There was very low quality evidence that people with resectable rectal cancer who receive combination preoperative chemotherapy have no improvements in overall survival or disease-free survival. There was high quality evidence that suggested that combination chemotherapy with oxaliplatin may improve local tumour control in people with resectable rectal cancer, but this regimen also caused more toxicity. The review included four RCTs but only one reported survival; therefore, we cannot make robust conclusions or useful clinical recommendations. The publication of more survival data from these studies will contribute to future analyses.