Universal Testing to Identify Lynch Syndrome Among Women With Newly Diagnosed Endometrial Carcinoma

Abstract Background Lynch syndrome (LS) is an autosomal dominant cancer syndrome caused by a germline mutation in the mismatch repair (MMR) genes. Protocols based on immunohistochemical expression of MMR proteins in cancer are used to identify patients with LS. Methods The universal LS screening protocol of the Tom Baker Cancer Centre (Calgary, AB) of all patients diagnosed between April 1, 2013 and April 1, 2015 with endometrioid carcinoma of the endometrium was audited through a retrospective chart review. LS status and frequency of protocol compliance at each of the key steps were calculated (Canadian Task Force Classification II-2). Results The cohort consisted of 375 patients. MMR immunohistochemical testing was requested for 321 (85.6%). Expression of at least one protein was lost in 86 (26.8%). Twenty-one (6.5%) patients were eligible for genetic counselling because PMS2, MSH2, or MSH6 protein expression was lost in 19, and two patients had a family history of LS. Eleven (91.7%) of 12 (57.1%) who attended had germline testing, and six (54.5%) showed a mutation diagnostic of LS. LS status among the cohort of 375 patients was positive in six (1.6%), negative in 294 (78.4%), and unknown in 75 (20%) because of protocol non-compliance. LS was confirmed in six (2%) of the 321 women who completed the protocol. Conclusion This is the first audit of a Canadian-based universal LS screening protocol of patients with endometrial cancer. The success of the protocol is endorsed by the 80% compliance and by the 2% prevalence of LS, which is within the published range.