ThTP7.2 For T4 rectal cancers (low) undergoing abdominoperineal resection (APER), should surgery be based on baseline MRI or Preoperative scans?

Abstract

Abstract Background Neoadjuvant therapy is standard of care for locally advanced rectal cancer. For low Rectal cancer which are T4 and require surgery after neoadjuvant treatment, there is a dilemma whether plane of surgery should be based on primary MRI or restaging MRI. At our institute surgery is based on Preoperative MRI scans. Methods To test this hypothesis, we compared outcomes of low Rectal cancers which were T3MRF (mesorectal fascia) positive (high risk) i.e group A to T4 rectal cancers, i.e group B who underwent APER after neoadjuvant therapy. Patients who underwent pelvic exenteration for persistent disease, or those who went on wait and watch programme were excluded. Results Between June 2010- July 2022, 953 APER were performed for low rectal cancers (adenocarcinoma) at our institute. Keeping follow-up in mind, we included 311, T3 MRF-positive patients and 101 T4 patients operated between 2010-2018. Group B patients included a higher number of females, lower BMI, and had a higher incidence of consolidation chemotherapy and short-course radiation. They were more likely to undergo extended TME compared to Group A (33.33%) vs (50.16%). This group also had higher blood loss and morbidity. In terms of oncological outcomes, circumferential margin involvement and local recurrence (isolated + systemic) in 2 groups were similar, Group A(37.12%) and (9.35%) compared to group B (11.11%) and (6.93%). There was no difference in 5 year disease free or overall survival. Conclusion T4 low rectal cancers, APER after neoadjuvant therapy can be based on preoperative MRI scans with no detrimental outcomes.