An MRI-based Assessment of Standard and Extralevator Abdominoperineal Excision Specimens: Time for a Patient Tailored Approach?

Background. The extralevator abdominoperineal excision (ELAPE) has been proposed as oncologically superior to standard abdominoperineal excision (SAPE). However, little is known regarding comparative margins achieved in ELAPE and SAPE. The purpose of this study was to compare patterns of tissue removal between these two groups that can aid patient selection. Methods. Twenty APE specimens, comprising 10 SAPEs and 10 ELAPEs, were selected randomly from a single UK centre. Transverse slices of pathological specimens were matched to corresponding axial MRI images obtained from conventional pelvic MRI imaging. Measurements from the muscularis propria to the resection margin [muscularis to margin (MTM) distance] were recorded by height (from anal verge) and quadrant for each surgical group. MTM distances achieved on histopathological assessment were also compared to MRI assessed distances necessary to achieve a clear CRM. Results. ELAPE specimens had a greater mean MTM distance than for SAPE (7.75 vs. 5.61 mm, p = 0.02). ELAPE had significantly greater MTM distances in lateral and posterior quadrants (p < 0.05) than SAPE at 30-49 mm. There was no significant difference in mean anterior distances (1.57 vs. 1.16 mm, p = 0.507) with the smallest difference at a height of 60-69 mm. Two (2 %) of pathological MTM distances within ELAPE group failed to achieve the minimum MRI assessed distance compared with 30 (23 %) in the SAPE group, which had higher CRM positivity. Conclusions. ELAPE appears to confer oncological benefit over SAPE but with notable exceptions, including tumours located above and below the puborectalis sling and anteriorly at the level of prostate where exenteration may be more appropriate.