Retrospective study of watch-and-wait in locally advanced rectal cancer patients with residual mucin on MRI following neoadjuvant therapy

Neoadjuvant therapy (NAT) leads to a clinical complete response (cCR) in a significant proportion of patients with locally advanced rectal cancer (LARC), allowing for possible nonoperative management. The presence of mucin in the tumor bed on MRI after NAT leads to uncertainty about residual disease and appropriateness of watch-and-wait (WW) strategy in patients with no evidence of disease on proctoscopy (endoscopic cCR). A retrospective study at Memorial Sloan Kettering Cancer Center (New York, NY) included 71 patients with mucin on post-NAT MRI: 20 with a cCR and 51 who had abnormalities on endoscopy. Nineteen patients chose WW. Of these, 15 (79%) had no local regrowth with median follow-up of 50 months (range 29-76), while 4 (21%) experienced regrowth between 19 and 29 months after NAT. Among 49 patients undergoing surgery, 5 (10%) had a pathologic complete response. The authors conclude that the presence of mucin after NAT for LARC does not preclude WW management in otherwise appropriate candidates who achieve an endoscopic cCR.