The Impact of Mesorectal Fat Area on Long-Term Outcomes Following Proctectomy for Lower Rectal Cancer

Background The mesorectal fat area (MFA) at the tip of the ischial spines on magnetic resonance imaging has been used to characterize mesorectal morphology. Recent studies reported that a larger MFA correlated with difficulties in rectal cancer surgery. However, the relationship between MFA and prognosis in rectal cancer remains unclear. This study evaluated the impact of MFA on long-term outcomes following robotic proctectomy for rectal cancer. Methods Patients who underwent robotic proctectomy for lower rectal cancer from December 2011 to December 2016 were enrolled. Cox regression analysis was performed to determine variables associated with relapse-free survival (RFS). Patients were divided into groups based on the MFA, and long-term outcomes were compared. Results Of 230 patients, 173 (75.3%) were male. The median age was 63 years, and median MFA was 19.7 cm 2 . In multivariate analysis, smaller MFA (hazard ratio [HR], 0.92; 95% confidence interval [CI], 0.87–0.98; p < 0.01), p/yp stage II (HR, 4.34; 95% CI, 1.71–11.03; p < 0.01), and p/yp stage III (HR, 6.02; 95% CI, 2.19–16.56; p < 0.01) were independently associated with worse RFS. In the median follow-up period of 60.8 months, patients with MFA < 20.7 cm 2 had a significantly lower 5-year RFS rate (72.6%) than those with MFA ≥ 20.7cm 2 (87.0%). Conclusions Smaller MFA was associated with worse RFS in patients undergoing robotic proctectomy for lower rectal cancer. MFA is considered to be a prognostic factor in rectal cancer.