Comparison of long course and short course preoperative radiotherapy in the treatment of locally advanced rectal cancer: a systematic review and meta-analysis.

BACKGROUND: rectal cancer (RC) is one of the most prevalent malignancies worldwide and different preoperative radiotherapies may lead to different outcomes. This meta-analysis aimed to compare the effectiveness of long-course (LC) and short-course radiotherapy (SC), with or without chemotherapy, for locally advanced rectal cancer.

METHODS: studies published up to March 31st 2018 were retrieved from PubMed, Medline, Cochrane and EMABSE. Randomized control or consort control trials that reported the outcomes of short or long course radiotherapy were eligible. Either a fixed or random effects model was used to access the overall combined risk estimates.

RESULTS: sixteen studies with a total of 2,773 RC patients were included in the analysis. There were no significant differences between LC and SC therapies with regard to the following: pathological complete response (PCR) (I2 = 78%, p < 0.05, RR = 0.54, 95% CI: 0.26-1.10); tumor downstaging (I2 = 79%, p < 0.05, RR = 0.83, 95% CI: 0.58-1.17); local recurrences (I2 = 22%, p = 0.27, RR = 0.55, 95% CI: 0.26-1.16); distant metastases (I2 = 29%, p = 0.22, RR = 1.03, 95% CI: 0.77-1.37); mortality (I2 = 0%, p = 0.78, RR = 0.95, 95% CI: 0.78-1.15) and serious late toxicity (I2 = 74%, p = 0.01, RR = 1.10, 95% CI: 0.37-3.26). In the subgroup analysis, LC had a better PCR and tumor downstaging rate compared with SC in the RCT subgroup. Besides, LC also presented a better PCR rate compared with SC without chemotherapy.

CONCLUSIONS: LC and SC are both effective in the preoperative treatment of RC with regard to PCR, tumor downstaging, local recurrences, distant metastases, mortality and serious late toxicity. Furthermore, chemotherapy may enhance the efficacy of preoperative treatment.