Universal screening for Lynch Syndrome in a large consecutive cohort of Chinese colorectal cancer patients: high prevalence and unique molecular features.

Jiang W1,2, Cai M1,3, Li S4, Bei J1,5, Wang F1,6, Hampel H7, Ling Y1,3, Frayling IM8,9, Sinicrope FA10, Rodriguez-Bigas MA11, Dignam JJ12, Kerr DJ13, Rosell R14, Mao M4, Li J15, Guo Y1,5, Wu X1,6, Kong L1,2, Tang J1,2, Wu X1,2, Li C16, Chen J1,5, Ou Q1,2,5, Ye M4, Guo F4, Han P4, Wang Q17, Wan D1,2, Li L18, Xu R1,19, Pan Z1,2, Ding P1,2.

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Abstract

The prevalence of Lynch syndrome (LS) varies significantly in different populations, suggesting that ethnic features might play an important role. We enrolled 3330 consecutive Chinese patients who had surgical resection for newly diagnosed colorectal cancer. Universal screening for LS was implemented, including immunohistochemistry for mismatch repair (MMR) proteins, BRAFV600E mutation test and germline sequencing. Among the 3250 eligible patients, MMR protein deficiency (dMMR) was detected in 330 (10.2%) patients. Ninety-three patients (2.9%) were diagnosed with LS. Nine (9.7%) patients with LS fulfilled Amsterdam criteria II and 76 (81.7%) met the revised Bethesda guidelines. Only 15 (9.7%) patients with absence of MLH1 on IHC had BRAFV600E mutation. One third (33/99) of the MMR gene mutations have not been reported previously. The age of onset indicates risk of LS in patients with dMMR tumors. For patients older than 65 years, only 2 patients (5.7%) fulfilling revised Bethesda guidelines were diagnosed with LS. Selective sequencing of all cases with dMMR diagnosed at or below age 65 years and only of those dMMR cases older than 65 years who fulfill revised Bethesda guidelines results in 8.2% fewer cases requiring germline testing without missing any LS diagnoses. While the prevalence of LS in Chinese patients is similar to that of Western populations, the spectrum of constitutional mutations and frequency of BRAFV600E mutation is different. Patients older than 65 years who do not meet the revised Bethesda guidelines have a low risk of LS, suggesting germline sequencing might not be necessary in this population. This article is protected by copyright. All rights reserved.