Cancer susceptibility gene mutations in type I and II endometrial cancer

To determine the incidence of germline cancer predisposition gene mutations in patients with endometrial cancer (EC) subtypes.

Germline DNA was extracted from whole blood collected from consenting patients undergoing primary surgery for EC between 5/2005 and 11/2016. DNA samples were evaluated by product sequencing from a targeted multiplex PCR panel including 21 known/suspected cancer predisposition genes. Variants were classified as pathogenic/likely pathogenic based on allele frequency (<0.003), effects on protein function, and ClinVar assertions.

Germline panel testing was performed on 1170 cases of EC; 849 (72.6%) were type I, and 321 (27.4%) were type II EC, including 135 (11.5%) uterine serous cancers (USC). BRCA1 mutations were enriched in Type II EC compared to Type I EC (0.93% vs. 0.12%, p = 0.07). Lynch Syndrome (LS) mutations were identified in 1.4% of type I and 1.6% of type II EC (p = 0.79), including 1.5% for USC. In total, predisposition gene mutations were present in 4.2% of type I and 5.3% of type II EC, as well as 6.7% of patients with USC).

BRCA1/2 and Lynch mutations were rare in this cohort of unselected patients with type I and II EC, including USC. However, the presence of predisposition gene mutations in 4.2% of EC type I, 5.3% of EC type II, and 6.7% of USC suggests that somatic mutation testing should be considered for all EC patients.