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

BACKGROUND

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.

OBJECTIVES

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.

SEARCH METHODS

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.

SELECTION CRITERIA

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.

DATA COLLECTION AND ANALYSIS

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.

MAIN RESULTS

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) 1.23, 95% confidence interval (CI) 1.04 to 1.46), 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.

AUTHORS' CONCLUSIONS

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.

Chemoradiotherapy and adjuvant chemotherapy for rectal cancer

Local recurrence is an important factor in determining the outcome of patients after surgery for rectal cancer, and various attempts have been made to reduce the local recurrence rate. Randomized controlled trials have shown that radiotherapy combined with total mesorectal excision can reduce the local recurrence rate in rectal cancer patients who undergo curative surgery. Chemoradiotherapy is more effective in achieving local control than radiotherapy alone, and preoperative chemoradiotherapy is superior to postoperative chemoradiotherapy in terms of adverse events. Recent advances have led to the identification of potential therapeutic targets such as epidermal growth factor receptor, vascular endothelial growth factor, and endothelial receptors. These new agents have been used in combination with conventional chemoradiotherapy, and higher pathological complete response rates have been reported for such combinations in comparison with conventional regimens. With regard to lateral node dissection, a recent study showed that postoperative chemoradiotherapy was more effective in reducing the local recurrence rate than lateral node dissection. As for adjuvant chemotherapy, one randomized controlled trial showed that patients who received uracil and tegafur as adjuvant therapy had significantly prolonged relapse-free survival times and overall survival times. As well, one metaanalysis has shown the efficacy of oral uracil-tegafur as adjuvant chemotherapy for rectal cancer.