Potential Cure of Rectal Cancer after Neoadjuvant Concurrent Chemoradiotherapy with Clinical Complete Response after Local Treatment

Background: Neoadjuvant chemoradiotherapy (NCRT) followed by total mesorectal excision is the standard treatment for patients with clinical stage II–III rectal cancer. Patients with ultra-low rectal cancer with comorbidities, clinical complete response (cCR), and no clinically or radiologically detectable disease after NCRT are managed using rectal-sparing approaches such as local treatment (LT) or a watch-and-wait (W and W) policy. Aim: This study aimed to analyze current single-center evidence of clinical outcomes regarding local control, distant recurrence, and survival by comparing rectal-sparing strategies such as LT and a W and W policy for patients with rectal cancer and cCR after NCRT. Methods: We enrolled 38 patients with rectal cancer and cCR who underwent neoadjuvant concurrent chemoradiotherapy (CRT) between January 2008 and December 2022 at Tri-Service General Hospital. About 15 and 23 patients who underwent local excision and were managed under a W and W policy were defined as the study and control groups, respectively. Rectal tumor-related characteristics were compared between both groups, and the risk factors predicting rectal tumor recurrence were assessed and presented as odds ratios (ORs). Five-year disease-free survival (DFS) was presented as a Kaplan–Meier survival curve. Results: The tumor recurrence rate was statistically significantly lower in patients with rectal cancer after concurrent CRT with cCR who were managed under the LT. Pretreatment carcinoembryonic antigen (CEA) levels and differentiation scores were statistically significantly higher on univariate Cox regression analysis regarding potential variables associated with recurrence in the W and W subgroup ( P = 0.018 and 0.021, respectively). Multivariate Cox regression analysis showed that old age could predict recurrence ( P = 0.040; OR = 1.120). The Kaplan–Meier curve showed no difference in 5-year DFS between groups. Conclusion: Patients with rectal cancer who received NCRT with cCR managed with LT did better than those under a W and W policy regarding distant recurrence, but with fair survival. Old age, higher pretreatment CEA levels, and advanced tumor differentiation type are the features of recurrence in patients with rectal cancer after NCRT. Therefore, cCR followed by a W and W policy and old age could predict recurrence in this subgroup.