Universal screening for Lynch syndrome in endometrial cancer diagnoses in Auckland, New Zealand: The initial experience.

Background: Universal mismatch repair immunohistochemistry (MMR IHC) tumour testing in endometrial cancer (EC) for Lynch syndrome (LS) was introduced in Auckland, New Zealand, in January 2017. Identifying patients with LS allows them and their families to access risk reduction strategies. Universal MMR IHC testing aids in the molecular classification of EC and has prognostic and therapeutic implications.

Aim: We aimed to determine the incidence of LS in women with EC in Auckland, New Zealand, following the introduction of MMR testing and the impact of universal screening on local genetic services.

Materials and methods: This is a retrospective clinicopathological evaluation of women with a new EC diagnosis referred to the Auckland Gynaecological Oncology Unit from 1/1/17 to 31/12/18. Patient data were extracted from the Gynaecological Oncology Unit database and electronic records, and analysed using descriptive statistics.

Results: During the study period, 409 patients were diagnosed with EC, with an over-representation of Pacific Islanders (32.5%). Of these, 82.6% underwent MMR IHC testing, 20% were MMR-deficient (MMRd), and 71% had somatic hypermethylation. The Pacific Islander population had a 64% (odds ratio 0.36, P = 0.005) reduction in the odds of having MMRd tumours compared with Europeans. Of the patients who underwent MMR IHC testing, 5.5% were referred to a genetic clinic for germline testing. LS was confirmed in eight patients (2.3%).

Conclusion: LS was diagnosed in 2.3% of patients. There was an over-representation of Pacific Islanders in the EC group but not among those diagnosed with LS.