PD-1 inhibitor treatment effective for localized mismatch repair-deficient colorectal cancer

For localized mismatch repair-deficient (dMMR) colorectal cancer (CRC), neoadjuvant programmed death-1 (PD-1) inhibitor treatment is effective, according to a study published online Jan. 11 in the Journal of the National Comprehensive Cancer Network.

Bin-Yi Xiao, M.D., from the Sun Yat-sen University Cancer Center in Guangzhou, China, and colleagues examined the efficacy and feasibility of neoadjuvant anti-PD-1 treatment for localized dMMR CRC among 73 patients, aged 18 to 75 years.

The researchers found that most of the tumors were locally advanced, including 26.0 and 39.7 percent T4a and T4b, respectively. PD-1 inhibitor monotherapy was received by 79.5 percent of the participants. Overall, 84.9 percent of the patients achieved objective response per radiologic assessment, including 17 and 45 patients (23.3 and 61.6 percent) with complete response (CR) and partial response, respectively, with a median of 9.6 weeks to response. The response rate was similar for patients with T4a/T4b disease and those with T2-3 disease (84.0 versus 85.4 percent).

In most of the 50 patients undergoing surgery (57.1 percent), pathologic CR was achieved, and remained high (59.5 percent) even for the 38 patients with T4a/T4b disease. Surgery was not performed in the 17 patients with CR but a watch-and-wait strategy was adopted. The median recurrence-free and overall survivals were not reached after a median of 17.2 months. The two-year tumor-specific disease-free and overall survival rates were 100 percent among patients undergoing surgery or achieving CR.

"Care providers, especially surgeons, should refrain from scheduling immediate surgery for patients with locally advanced, or even early-stage dMMR/microsatellite instability-high colorectal cancer," a coauthor said in a statement.

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