EP665 - Local recurrence after transanal surgery of rectal adenocarcinoma in the setting of neoadjuvant or adjuvant chemoradiotherapy

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Purpose/Background: Rectal cancer continues to challenge surgeons and patients striving to improve quality of life while maximizing surgical intervention survival benefit. Recent data suggest excellent outcomes with neoadjuvant or adjuvant therapy combined with either transanal excision (TAE) or transanal minimally invasive surgery (TAMIS). Our goal was to identify all rectal cancers presenting to a high-volume referral center that received any transanal surgery in conjunction with neoadjuvant or adjuvant therapy and examine the patterns of recurrence.

Methods/Interventions: A retrospective chart review of all transanal surgeries from 2011 through 2023 was performed for a single-center of eight colorectal surgeons. Patients whose surgeries with pathology for rectal adenocarcinoma were reviewed for complete staging, age, BMI, continence, neoadjuvant/adjuvant therapy status, surgical approach, final pathology, recurrence, death, and cancer-related death.

Results/Outcomes: Of the 232 transanal surgeries performed during the study period, 82 were for rectal adenocarcinoma. The average distance of tumor to the anal verge was 4.3 cm (+/- 2.3 cm). Overall, the pre-treatment clinical stage was mostly T1N0M0 (62%, n=51) based on either MRI or ERUS, the remaining were staged as T2 (n=15), T3 (n=12), T4b (n=2), Tis (n=1), and missing (n=1).

Twenty percent (n=16) received neoadjuvant chemoradiotherapy after review by the multidisciplinary tumor board. Final pathology of this group was T1 (n=7), T2 (n=8), T3 (n=1). R0 resection rate was 82% (n=14). Recurrence rates were 37.5% (n=6) and rates of radical surgery were 44% (n=7). Sites of recurrence after TAE were at the resection site (n=2), pelvic nodule or pelvic floor involvement (n=2), iliac lymph node (n=1), and liver (n=2), one with synchronous resection site recurrence.

The majority (n=66, 80%) underwent surgery first. Final pathology was Tis (n=2), T1 (n=41), T2 (n=20), T3 (n=2), T4 (n=1) and the R0 resection rate was 88% (n=58). 32% underwent adjuvant (n=21) therapy. 12 patients (16%) received radical surgery after TAE based on pathology (n=6) or due to recurrence (n=6). No recurrence was seen in patients receiving radical surgery immediately after TAE. Overall recurrence rates were 18% (n=12). Of patients with recurrence, 58% (n=7) did not have adjuvant therapy. Recurrence in patients without adjuvant therapy were mostly at the resection site (n=6; 2 with metachronous pulmonary metastasis), or liver metastasis (n=1). The recurrence rates in those receiving adjuvant therapy was 24% (resection site [n=1], inguinal lymph node [n=1], liver [n=1], lung [n=2]).

The greater than clinical stage 1 cohort had a 28% cancer-related mortality. Overall 30-day complication rate was 11% (n=9) consisting of bleeding, fistula, incontinence, and abscess.
Overall mortality of the entire cohort was 30% (n=34) with cancer-specific mortality of 13.4% (n=11).

Conclusion/Discussion: Despite the use of neoadjuvant or adjuvant chemoradiotherapy in conjunction with local excision, recurrence rates after transanal excision remain high. In the absence of additional chemoradiotherapy, recurrence is most frequently seen at the site of excision. The pattern of recurrence is more variable in those who receive neoadjuvant or adjuvant therapy. Careful multidisciplinary review is warranted when considering local excision for rectal cancer.