Risk Stratification Based on Endoscopic Ulcerative Findings in Patients with Endoscopic Non-Complete Response after Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer

Few studies have evaluated ulcerative findings after chemoradiotherapy (CRT) or total neoadjuvant therapy (TNT) for rectal cancer. This study aimed to evaluate risk stratification based on ulcerative findings and their association with pathological non-complete response (pNon-CR) in patients classified as endoscopic non-complete response (eNon-CR).

Among patients with stage II/III rectal adenocarcinoma who underwent surgery after CRT or TNT between April 2018 and March 2025, those diagnosed with eNon-CR at the final preoperative endoscopy were included. The eNon-CR endoscopic findings were defined as the presence of definite neoplastic nodules, ulceration, poor wall distensibility, and neoplastic pits or tumor vessels under magnification. Ulcerative lesions without other tumor-related endoscopic findings, even under magnifying endoscopy, were defined as isolated ulcers and degree of depression (shallow/deep), and association with pNon-CR was analyzed.

In total 154 patients were analyzed. Of these, 18 (11.7%) achieved pathological complete response. Isolated ulcers (n=22) had a positive predictive value (PPV) for pNon-CR of 63.6% (95% confidence interval [CI]: 40.7-82.8), whereas ulceration with neoplastic pits or tumor vessels identified by magnifying endoscopy (n=13) had a PPV of 84.6% (95% CI; 54.6-98.1). When isolated ulcers were subclassified, shallow ulcers (n=5) had a low PPV of 20.0% (95% CI: 5.0-71.6), whereas deep ulcers (n=17) had a PPV of 76.5% (95% CI: 50.1-93.2) (p = 0.039).

In the endoscopic evaluation of ulcerative findings, magnifying endoscopy may be helpful for assessing eNon-CR. Subclassification of isolated ulcers may aid in the risk stratification of eNon-CR.