Prognostic value of Lynch syndrome, BRAF^V600E, and RAS mutational status in dMMR/MSI‐H metastatic colorectal cancer in a pooled analysis of Dutch and French cohorts

Abstract

BackgroundCurrent knowledge on prognostic biomarkers (especially BRAFV600E/RAS mutations) in metastatic colorectal cancer (mCRC) is mainly based on mCRC patients with proficient mismatch repair (pMMR) tumors. It is uncertain whether these biomarkers have the same prognostic value in mCRC patients with deficient mismatch repair (dMMR) tumors.MethodsThis observational cohort study combined a population‐based Dutch cohort (2014–2019) and a large French multicenter cohort (2007–2017). All mCRC patients with a histologically proven dMMR tumor were included.ResultsIn our real‐world data cohort of 707 dMMR mCRC patients, 438 patients were treated with first‐line palliative systemic chemotherapy. Mean age of first‐line treated patients was 61.9 years, 49% were male, and 40% had Lynch syndrome. BRAFV600E mutation was present in 47% of tumors and 30% harbored a RAS mutation. Multivariable regression analysis on OS showed significant hazard rates (HR) for known prognostic factors as age and performance status, however showed no significance for Lynch syndrome (HR: 1.07, 95% CI: 0.66–1.72), BRAFV600E mutational status (HR: 1.02, 95% CI: 0.67–1.54), and RAS mutational status (HR: 1.01, 95% CI: 0.64–1.59), with similar results for PFS.ConclusionBRAFV600E and RAS mutational status are not associated with prognosis in dMMR mCRC patients, in contrast to pMMR mCRC patients. Lynch syndrome is also not an independent prognostic factor for survival. These findings underline that prognostic factors of patients with dMMR mCRC are different of those with pMMR, which could be taken into consideration when prognosis is used for clinical decision‐making in dMMR mCRC patients and underline the complex heterogeneity of mCRC.

Epidemiological and clinicopathological features of KRAS, NRAS, BRAF mutations and MSI in Chinese patients with stage I–III colorectal cancer

“…[ 34 ] However, our finding is inconsistent with this report. Recently, a study reported that Lynch dMMR/MSI-H tumors more often harbored a RAS mutation (65%), [ 35 ] suggesting that the results observed in our study may be due to a potentially higher proportion of Lynch syndrome patients in the MSI-H group. The MMR gene status detection is crucial for the diagnosis of Lynch syndrome.…”

“…The mutation rate of 28% closely matches the results of the aforementioned study, where the A146 mutation rate reached 20% in the MSI-H group. [ 35 ] The high frequency of K117N/A146V/A146P/A146T mutations in the MSI-H group of our study may be one of the critical factors contributing to the overall increased KRAS mutation rate. Overall, it suggests that the exact relationship between KRAS mutations and MSI in the real world still requires further research to be determined.…”