• R Cohen, O Buhard, P Cervera, E Hain, S Dumont, A Bardier, J-B Bachet, J-M Gornet, D Lopez-Trabada, R Kaci, P Bertheau, F Renaud, F Bibeau, Y Parc, D Vernerey, A Duval, M Svrcek, and Thierry André.
• Department of Medical Oncology, Hôpital Saint-Antoine, AP-HP, 184 rue du Faubourg Saint-Antoine, Paris 75012, France; INSERM, Unité Mixte de Recherche Scientifique 938, Centre de Recherche Saint-Antoine, Equipe Instabilité des Microsatellites et Cancer, Equipe labellisee par la Ligue Nationale contre le Cancer, 184 rue du Faubourg Saint-Antoine, Paris 75012, France; Sorbonne Universités, UPMC Univ Paris 06, France. Electronic address: romain.cohen@aphp.fr.
• Eur. J. Cancer. 2017 Nov 1; 86: 266-274.

BackgroundPatients treated with chemotherapy for microsatellite unstable (MSI) and/or mismatch repair deficient (dMMR) cancer metastatic colorectal cancer (mCRC) exhibit poor prognosis. We aimed to evaluate the relevance of distinguishing sporadic from Lynch syndrome (LS)-like mCRCs.Patients And MethodsMSI/dMMR mCRC patients were retrospectively identified in six French hospitals. Tumour samples were screened for MSI, dMMR, RAS/RAF mutations and MLH1 methylation. Sporadic cases were molecularly defined as those displaying MLH1/PMS2 loss of expression with BRAFV600E and/or MLH1 hypermethylation and no MMR germline mutation.ResultsAmong 129 MSI/dMMR mCRC patients, 81 (63%) were LS-like and 48 (37%) had sporadic tumours; 22% of MLH1/PMS2-negative mCRCs would have been misclassified using an algorithm based on local medical records (age, Amsterdam II criteria, BRAF and MMR statuses when locally tested), compared to a systematical assessment of MMR, BRAF and MLH1 methylation statuses. In univariate analysis, parameters associated with better overall survival were age (P < 0.0001), metastatic resection (P = 0.001) and LS-like mCRC (P = 0.01), but not BRAFV600E. In multivariate analysis, age (hazard ratio (HR) = 3.19, P = 0.01) and metastatic resection (HR = 4.2, P = 0.001) were associated with overall survival, but not LS. LS-like patients were associated with more frequent liver involvement, metastatic resection and better disease-free survival after metastasectomy (HR = 0.28, P = 0.01). Median progression-free survival of first-line chemotherapy was similar between the two groups (4.2 and 4.2 months; P = 0.44).ConclusionsLS-like and sporadic MSI/dMMR mCRCs display distinct natural histories. MMR, BRAF mutation and MLH1 methylation testing should be mandatory to differentiate LS-like and sporadic MSI/dMMR mCRC, to determine in particular whether immune checkpoint inhibitors efficacy differs in these two populations.Copyright © 2017 Elsevier Ltd. All rights reserved.

46 keywords...

hide…