Most patients with microsatellite instability-high (MSI-H) colorectal cancer (CRC) do not have recurrence after cessation of immunotherapy treatment, according to a study published in Cancer Research Communications. Kristen Simmons, MD, and colleagues reviewed records from patients with advanced MSI-H CRC who received immunotherapy between 2014 and 2022 and stopped after prolonged clinical benefit. The researcher reviewed data for 64 patients with MSI-H CRC without progression on immunotherapy: 48 and 16 received a monoclonal PD-1 antibody alone or in combination with a CTLA-4 antibody, respectively. The median immunotherapy exposure was 17.6 months. The study team observed that 88% of patients remained without disease progression after a median follow-up of 22.6 months after stopping immunotherapy. Dr. Simmons and colleagues noted no associations between coexisting mutation, primary tumor sidedness, and immunotherapy. “These data provide important information that oncologists can use for guiding discussions with patients with MSI-H/mismatch repair deficiency [CRC] by providing clearer numbers for the likelihood of progression should they decide to stop their immunotherapy treatment,” senior author Van Karlyle Morris, MD, said in a statement.