Active surveillance program of patients with rectal cancer with a complete clinical response after prolonged chemoradiotherapy with consolidating chemotherapy

AIM: to determine the algorithm for selecting patients included in the ASP program after prolonged chemoradiotherapy (CRT) with consolidation chemotherapy (CCT). PATIENTS AND METHODS: the retrospective study included patients with adenocarcinoma of the low and middle rectum (2017 to 2024), who achieved cCR after CRT with CCT, which led to the decision to implement ASP. Radiotherapy was administered in a prolonged mode at a dose of 50–55 Gy with oral capecitabine intake. Between the completion of CRT and the first follow-up examination, 4 cycles of CCT were done in the FOLFOX6 regimen. Clinical tumor regression was assessed 4 weeks after the completion of CCT, based on the data from endoscopy, digital examination, and MRI. cCR was understood to refer to cases where, during endoscopic treatment performed after CRT and CCT at the site of the previously determined tumor, there were signs of a flat white/red scar. RESULTS: the study included 27 patients (15 (55.6%) men, 12 (44.4%) women). The patients' age ranged from 38 to 80 years (median 63 years). The median distance from the anal verge to the lower edge of the tumor was 4.5 (2.0–9.5) cm. Most patients had clinical stage III disease — 18/27 (66.7%), while the tumor size in the largest dimension ranged from 2.4 to 6.5 cm (median 4.0 cm). The median interval between the completion of CRT and the follow-up examination was 16 (9–25) weeks. MRI of the pelvic organs revealed TRG1 in 13/27 (48.1%) patients, TRG2 also in 13/27 (48.1%) and in one patient (3.7%) has a mucinous tumor that is not subject to standard TRG assessment. The MRI findings of all patients selected for ASP was characterized by fibrosis of the tumor bed without signs of residual tumor tissue/affected lymph nodes in the mesorectal tissue and deep layers of the wall, while both thin and full-thickness and split fibrous scars present, extending up to half the circumference. All patients who achieved cCR had a primary tumor of category up to T3b inclusive. With a median follow-up of 14.7 (3.8–80.2) months, tumor regrowth was observed in 2/27 patients (7.4%), both of whom underwent radical surgeries. Threeyear relapse-free survival rate was 81.1 ± 10.1%, while overall survival 95.2 ± 4.6%. CONCLUSIONS: the implementation of an ASP program after CRT should be based on careful selection of patients who have achieved cCR according to comprehensive check-up. It is advisable to begin the examination with MRI followed by endoscopy, as this approach provides all necessary information and avoids artifacts in MRI that may arise after endoscopy. Endoscopy plays a leading role in assessing the intraluminal tumor component, with the only manifestation of cCR being a flat white or red scar. © 2025 Elsevier B.V., All rights reserved.