Total neoadjuvant therapy compared with standard therapy in locally advanced rectal cancer: A systematic review and meta-analysis.

709 Background: Standard therapy of locally advanced rectal cancer (LARC) includes concurrent chemoradiotherapy (CRT) followed by surgery and adjuvant chemotherapy (CT). An alternative strategy known as Total Neoadjuvant Therapy (TNT) involves administration of CRT and CT prior to surgery with the goal of delivering uninterrupted systemic therapy to eradicate micrometastases. A comparison of these two approaches has not been reviewed previously. Methods: Following PRISMA guidelines, a systematic review of PubMed and Web of Science was performed from inception through September 2018 to identify studies which compared TNT with CRT in LARC. The outcomes of interest were pathologic complete response rates (PCR), sphincter-preserving surgery rates, ileostomy rates, disease-free survival (DFS) and overall survival (OS). Summary hazard ratios (HR) with 95% confidence intervals (CI) were estimated using a random effects model and heterogeneity was estimated using the inconsistency index (I2). Results: After reviewing 2,163 reports, 5 studies which compared CRT and TNT were selected for inclusion. These were reported from Europe and the United States and included a total of 1,134 patients of whom 552 received TNT. The pooled prevalence of PCR was 32.4% (range 17-28%) in the TNT group and 22.3% (range 4-21%) in the CRT group. In a meta-analysis of five studies, TNT was associated with a higher chance of achieving a pathologic complete response (OR 1.92; 95% CI 1.44- 2.57, I2= 22%). Recipients of TNT also had higher odds of receiving sphincter-sparing surgery (5 studies, OR 1.92; 95% CI 1.44- 2.57, I2= 0%) and lower odds of requiring an ileostomy (2 studies, OR 0.72; 95% CI 0.54- 0.96, I2= 0%). Only one study presented data on DFS and noted improved DFS in patients who received TNT (OR 0.72; 95% CI 0.54- 0.96). The impact of TNT relative to standard therapy on overall survival was not reported. Conclusions: Total Neoadjuvant Therapy is a promising strategy in locally advanced rectal cancer, with superior PCR rates compared to standard therapy. However, the long term impact on disease recurrence and overall survival remain unclear. These are best be studied in a prospective randomized clinical trial.