Background:The optimal management of primary tumor (PT) in microsatellite instability-high metastatic colorectal cancer patients treated with immune checkpoint inhibitors (ICIs) remains unclear. Patients and methods:We retrospectively analyzed a prospective, single-center cohort to assess PT outcomes in this setting.Results: Among 210 patients, 21% received first-line ICI; we focused on 33 patients (16%) without prior PT resection at ICI initiation.Early progressive disease (<6 months) occurred in 10 patients (5%), with eight deaths (<1 year); two underwent surgery for symptomatic PT.Among the remaining 23 patients (11%) with disease control (6 months), 15 had PT resection due to clinical events (n = 5) or for non-symptomatic reasons (n = 10), including seven with pathological complete response and eight with residual tumor.Eight patients had no PT resection, including two with metastatic and/or local progressive diseases.After a median 75-month follow-up, only six patients (3%) remained progression-free with PT in place and no residual endoscopic tumor.Conclusions: If PT is left in place at ICI initiation, close monitoring is required due to its specific evolution.Resection may be indicated for symptomatic stenosis.Prospective trials are needed to define the role of endoscopic monitoring and indication of PT resection in first-line ICI.
Mas et al. (Sat,) studied this question.