Meta-analysis of oncological outcomes of sigmoid cancers: A hidden epidemic of R1 "palliative" resections.
Colon cancer outcomes are now inferior to rectal cancer outcomes. The sigmoid colon is the most common site of colonic cancer. The aim of this review was to investigate the oncological outcomes for sigmoid cancer. A systematic review and meta-analysis was performed. We included any study of the oncological outcomes for sigmoid cancer such as local recurrence, distant recurrence and disease free survival. A systematic search was conducted in Medline from inception to November 2016. Study quality was evaluated with the Newcastle-Ottawa Scale. The study was registered on PROSPERO (CRD42017069326). The search terms returned 1323 results. We identified a total of 17 eligible studies including 5953 patients. The pooled local recurrence rate was 10.5% in 15 studies with 5148 patients (95% CI 0.07-0.14) and heterogeneity measured by I2 was 94%. The pooled distant recurrence rate was 19.5% (7 studies, 2040 patients, 95% CI (0.14-0.25), I2 90%). The pooled disease free survival at 5 years was 80.4% (5 studies, 2336 patients, 95% CI 78.6%-82.1%, I2 11.5%.). The median Newcastle-Ottawa score was 4 out of 9. R1 and R2 resections were excluded or not described in 16/17 studies. Two studies described R1 and R2 rates of 15-20%. The pooled local recurrence rate of sigmoid cancer of 10.5% is higher than contemporary rates of local recurrence of rectal cancer. A large number of papers fail to describe or include R1 resections of sigmoid cancer, which are frequently described as palliative.