Prognostic Significance of Partial Tumor Regression After Preoperative Chemoradiotherapy for Rectal Cancer: A Meta-analysis

BACKGROUND: Complete tumor regression after preoperative chemoradiotherapy for rectal cancer has been associated with better disease-free and overall survival. The survival experience for patients with partial tumor regression is less clear. OBJECTIVE: The aim of this meta-analysis was to evaluate the prognostic significance of partial response after preoperative chemotherapy on disease-free survival in rectal cancer patients. DATA SOURCES: Relevant studies were identified by a search of MEDLINE and EMBASE databases with no restrictions to October 31, 2012. STUDY SELECTION: We included long-course radiotherapy that reported the association between degree of tumor regression and disease-free survival of rectal cancer. INTERVENTIONS: Direct, indirect, and graph methods were used to extract HRs. MAIN OUTCOME MEASURES: Study-specific HRs on the disease-free survival were pooled using a random-effects model. Eleven articles in total were selected. Analysis was performed first among the 6 studies that separated partial response from the complete response and later among all 11 of the studies. RESULTS: Pooled HR was 0.49 (95% CI, 0.28-0.85) for the 6 studies that compared partial response with poor response. It was 0.41 (95% CI, 0.25-0.67) when all 11 of the studies were analyzed together. LIMITATIONS: The studies were limited by not being prospective, randomized trials, and the tumor regression grades were not uniform. CONCLUSIONS: Partial tumor response is associated with a 50% improvement in disease-free survival and should be considered as a favorable prognostic factor.