Oncologic outcomes of organ preservation in patients with rectal adenocarcinoma treated with total neoadjuvant therapy: A single-center study.

3598 Background: Total neoadjuvant therapy (TNT) reduces the risk of local recurrence and distant metastases in patients (pts) with locally advanced rectal cancer (RC). Selected pts who achieve a complete clinical response (cCR) after TNT who can undergo a strict surveillance protocol may be considered for non operative management (NOM) to preserve rectal function. Methods: We conducted an observational, retrospective, single-center study to evaluate watch-and-wait strategy in those achieved organ preservation & survival in pts with locally advanced or resectable metastatic pMMR RC treated with TNT. Pts received either induction chemotherapy followed by chemoradiation (INCT-CRT) or chemoradiation followed by consolidation chemotherapy (CRT-CNCT). INCT and CNCT consisted of 6-8 cycles of FOLFOX or 5 cycles of CAPEOX. CRT consisted of a total dose of 5,040-5,750 CGy to the tumor and lymph nodes along with capecitabine. Pts were assessed for treatment response with digital rectal exam, MRI, flexsig 8 weeks after TNT. Pts who achieved cCR or a near-cCR were offered NOM with WW. Close surveillance with the above-mentioned modalities was repeated every 3 months, CT chest/abdomen or PET scan was performed every 6 months. Data on local recurrence, distant metastases and survival was collected. Results: From Dec 2017 to Jan 2024, a total of 109 pts with RC went on WW after TNT in our center. Most pts were males (66%). Median age was 59 (30-88). The proportions of stages I to IV were 2.7%, 19.2%, %, 76.1%, and 3.6% respectively. After a median follow-up of 20.2 months, median time of sustained cCR was 67 weeks, tumor regrowth occurred in 7/109 (6.4%) pts. 3/109 pts developed distant metastases (8.5%). Median time from cCR to local regrowth/metastasis was 42 weeks. Recurrence was detected within the first 2 years in all 7 patients. 3/7 patients are in remission after salvage surgery, 2/7 pts were scheduled for surgery, 1/7 pts died of disease progression and another pt was a poor surgical candidate. 93% (102/109) of our pts are with no evidence of disease. Conclusions: Organ preservation for locally advanced rectal cancer is feasible and successful in a large community-based hospital system for selected pts who achieve cCR to TNT. WW is a reasonable and attractive strategy for both patients and oncologists that minimizes post-operative morbidity . Ongoing trials like JANUS aim at increasing cCR rate. Demographic and clinical characteristics of the pt cohort. Variables All pts (n=109) Age, median (years) 59.0 (30-88) Gender Male Female 73 (66%) 36 (34%) Ethnicity Caucasian Hispanic Other 78 (71.5%) 23 (21.1%) 8 (7.3%) Clinical stage at diagnosis I II III IV 3 (2.7%) 21 (19.2%) 83 (76.1%) 2 (1.8%) TNT Strategy NCT-CRT CRT-CNCT 45 (41.2%) 64 (58.8%) CT regimen FOLFOX CAPEOX Other 91 (84.4%) 14 (12.8%) 3 (2.7%) Months of follow-up, median 20.2 Tumor Grade 1 2 3 Unknown 7 (6.4%) 53 (48.6%) 2 (1.8%) 47 (43.11%)