The efficiency of neoadjuvant chemotherapy in colon cancer with mismatch repair deficiency

Colon cancers with mismatch repair deficiency (dMMR) have specific clinicopathologic characteristics compared with mismatch repair proficiency (pMMR); however, the effect of MMR status on the efficiency of neoadjuvant chemotherapy (NCT) remains unclear. In our study, 439 dMMR and 26 pMMR colon cancer patients with or without NCT from 2010 to 2017 were retrospectively collected. Clinicopathological features, treatment response, and survival were compared between different groups. In the dMMR group, patients with NCT were likely to have higher CEA (abnormal CEA: 51.6% vs. 17.4%, p < 0.001), more multiorgan resection (38.7% vs. 16.8%, p = 0.006), and larger postoperative tumor diameter (7.26 vs. 6.21, p = 0.033) than those without NCT, but nearly half of cT4b patients who had NCT (42.9%, 9/21) avoid multiorgan resection. pT4 stage (HR, 14.97; 95% CI, 1.88-118.92; p = 0.010), number of positive lymph nodes (HR, 1.17; 95% CI, 1.09-1.26; p < 0.001), and tumor deposit (HR, 6.73; 95% CI, 2.08-21.74; p = 0.001) were independent prognosis factors of disease-free survival (DFS). For the advanced tumor subset, there is no significant difference between patients with or without NCT for OS (p = 0.13) and DFS (p = 0.11), although the survival rate of NCT was higher than non-NCT patients. Moreover, tumor regression grade was similar between dMMR and pMMR patients who had NCT. This study showed that NCT was more likely to be employed in dMMR patients with advanced tumors and may reduce the rate of multiorgan resection for cT4b dMMR patients. More large-scaled researches are needed to further explore if MMR status could predict the efficacy of neoadjuvant chemotherapy in patients with colon cancer.