BACKGROUND: The “wait-and-see” policy instead of standard surgery for patients with rectal cancer who undergo a complete tumor regression after chemoradiation treatment is highly controversial. It is not clear yet how patients should be monitored once they are managed nonoperatively and whether follow-up by MRI has any potential role.
OBJECTIVE: This study aimed to describe the rectal wall MRI morphology during short-term and long-term follow-up in patients with a clinical complete tumor response undergoing a wait-and-see policy without surgical treatment.
DESIGN, SETTING, AND PATIENTS: As part of an observational study in our center, a cohort of 19 carefully selected patients with a clinical complete response after chemoradiation was managed with a wait-and-see policy and followed regularly (every 3–6 mo) by clinical examination, endoscopy with biopsies, and a rectal MRI. The MR morphology of the tumor bed was studied on the consecutive MRI examinations.
MAIN OUTCOME MEASURES: The primary outcome measured was the morphology of the tumor bed on the consecutive MRI examinations performed during short-term (≤6 mo) and long-term (>6 mo) follow-up.
RESULTS: Patients with a complete tumor response after chemoradiation presented with either a normalized rectal wall (26%) or fibrosis (74%). In the latter group, 3 patterns of fibrosis were observed (full-thickness, minimal, or spicular fibrosis). The morphology patterns of a normalized rectal wall or fibrosis remained consistent during long-term follow-up in 18 of 19 patients. One patient developed a small, endoluminal recurrence, which was salvaged with transanal endoscopic microsurgery. In 26% of patients, an edematous wall thickening was observed in the first months after chemoradiation, which gradually decreased during long-term follow-up. Median follow-up was 22 months (range, 12–60).
LIMITATIONS: This was a small observational study, and had no histological validation.
CONCLUSIONS: Four MR patterns of a persistent complete response of rectal cancer after chemoradiation were identified. These MR features can serve as a reference for the follow-up in a wait-and-see policy.