[Application value of colonoscopic assessment in "watch and wait" strategy for mid-lower rectal cancer after...

Objective: To investigate the value of colonoscopic assessment in "watch and wait" strategy for mid-lower rectal cancer after neoadjuvant chemoradiotherapy (nCRT). Methods: A single-center retrospective case series study was performed. Database of mid-lower rectal cancer patients at Department of Gastrointestinal Oncology, Peking University Cancer Hospital & Institute from March 2011 to June 2017 was retrieved. Inclusion criteria: (1) nCRT was completed (50.6 Gy/22 f, plus oral capecitabine); (2) radical surgery was performed within 12 weeks after nCRT treatment; (3) clinical response to nCRT was determined as clinical complete response (cCR) or near-cCR. Patients who did not undergo colonoscopy and MRI in our center during initial assessment and follow-up, or whose colonoscopy data were unable to re-evaluated, were excluded. Initial evaluation of nCRT response was carried out between 6 and 16 weeks after nCRT. The results of endoscopy (eCR, near-eCR and non-eCR) and MRI (mCR, near-mCR and non-mCR) were compared to local lesion relapse during follow-up. The consistency of the results of colonoscopy and MRI was evaluated by Kappa test (Kappa value of 0.21 to 0.40 indicates general consistency, 0.41 to 0.60 moderate consistency, and 0.61 to 0.80 high consistency). The non-regrowth disease-free survival (NR-DFS) curves of the eCR group and the near-eCR group were plotted by Kaplan-Meier method and compared by log-rank test. Clinical significance of colonoscopy examination in the following "watch and wait" strategy during follow-up period was analyzed. Results: A total of 32 patients were enrolled in the study, including 21 (65.6%) males and 11 (34.4%) females with a median age of 57 years old. The differentiated type of rectal cancer included 1 (3.1%) case of well-differentiated, 26 (81.2%) of moderately differentiated and 5 (15.6%) of poorly differentiated. Clinical stage of the patients included 9 (28.1%) cases of T2-3N0 and 23 (71.9%) of T2-3N+. Median follow-up period was 48 (18 to 80) months. The local regrowth rate was 34.4% (11/32) and median interval of local regrowth was 10.0 (4 to 37) months. Initial colonoscopy evaluation was carried out at a median time of 9 (5 to 19) weeks after nCRT was completed. According to endoscopic findings, patients were divided into 3 groups, including 15 cases in eCR group, 15 cases in near-eCR group and 2 cases in non-eCR group. According to the appearance of MRI, patients were divided into 3 groups, including 8 cases in mCR group, 21 cases in near-mCR group and 3 cases in non-mCR group. The regrowth rate of eCR group was lower than that of mCR group (1/15 vs. 1/8) without significant difference (P=1.000). The regrowth rate of near-eCR group was higher than that of near-mCR group [9/15 vs. 42.9% (9/21)] without significant difference as well (P=0.500). The consistency between colonoscopy and MRI in response evaluation of cCR or near-cCR after nCRT was unsatisfactory (Kappa=0.341, P=0.011). After initial evaluation, 31 patients underwent watch and wait strategy, and 1 underwent local resection. The 1- and 3-year NR-DFS in the eCR group was both 100%, which was higher than that in the near-eCR group (53.3% and 38.9%, respectively), and the difference was statistically significant (P=0.001). During watch and wait period, 11 cases developed local regrowth by colonoscopy examination and the biopsy result included 4 case of high-grade intraepithelial neoplasia (HIN), 6 cases of adenocarcinoma and 1 case of chronic mucosal inflammation. Meanwhile lateral developmental tumor of ascending colon in 1 case and of sigmoid in a case was found by colonoscopy and confirmed as HIN by postoperative pathology. Besides, 4 cases developed colonic multiple adenoma and all underwent endoscopic resection. Conclusion: Colonoscopy examination plays an important role in both initial assessment and regrowth monitoring during watch and wait strategy after nCRT treatment.