Association between microsatellite instability and tumor response to neoadjuvant chemoradiotherapy for rectal cancer

Abstract

Purpose The relationship between microsatellite instability (MSI) and tumor response after neoadjuvant chemoradiotherapy (nCRT) in rectal cancer remains unclear. The present study aimed to evaluate the association between MSI and tumor response to nCRT in rectal cancer treatment. Methods Patients with rectal cancer from 2 tertiary hospitals who underwent nCRT, followed by radical surgery, were included. The microsatellite status was determined using a PCR-based Bethesda panel. Tumors with a Dworak’s tumor regression grade of 3 or 4 were considered to have a good response. Predictive factors for a good response to nCRT were analyzed. Results Of the 1,401 patients included, 910 (65.0%) had MSI results and 1.5% (14 of 910) showed MSI-H. Among all the patients, 519 (37.0%) showed a good response to nCRT. A univariate analysis showed that MSI-H tended to be negatively associated with a good response to nCRT, but no statistical significance was observed (7.1% vs. 24.1%, P = 0.208). Multivariate analysis showed that well-differentiated tumors were the only predictive factor for good response to nCRT (odds ratio [OR], 2.241; 95% confidence interval [CI], 1.492–3.364; P < 0.001). MSI status tended to be associated with the response to nCRT (OR, 0.215; 95% CI, 0.027–1.681; P = 0.143). Conclusion MSI-H was not associated with response to nCRT in patients with rectal cancer.

Different oncological features of colorectal cancer codon-specific KRAS mutations: Not codon 13 but codon 12 have prognostic value

“…Previous studies have shown that the combination of KRAS mutations and MSI status is a potential prognostic factor in various stages of CRC [ 26 , 32 - 36 ]. In addition, since MSI status is associated with chemoresistance[ 37 , 38 ], the MSS/MSI-low and MSI-high subgroups were analyzed separately to eliminate the effect of MSI status on prognosis. Interestingly, in the MSS/MSI-low patient subgroup, only KRAS codon 12 mutation was statistically related to recurrence, whereas there was no association between codon-specific KRAS mutations and recurrence among MSI-high tumors.…”