Mainstreaming germline BRCA1/2 testing in non-mucinous epithelial ovarian cancer in the North West of England

Poly(ADP-ribose) polymerase (PARP) inhibitors improve survival in BRCA-mutant high grade serous ovarian carcinoma. As a result, germline and somatic BRCA1/2 testing have become standard practice in women diagnosed with ovarian cancer. We outline changes in testing and detection rates of germline BRCA1/2 pathogenic variants (PVs) in cases of non mucinous EOC diagnosed during three eras, spanning 12 years, within the North West of England and compare the uptake of cascade testing in families identified by oncology-led mainstreaming versus regional genetics clinics. Eras included: Period 1 (20% risk threshold for testing): between Jan/07 and May/13; Period 2 (10% risk threshold for testing): between Jun/13 and Oct/17 and; Period 3 (mainstream testing): between Nov/17 and Nov/19. A total of 1,081 women underwent germline BRCA1/2 testing between Jan/07 and Nov/19 and 222 (20.5%) were found to have a PV. The monthly testing rate increased by 3.3-fold and 2.5-fold between Periods 1 to 2 and Periods 2 to 3, respectively. A similar incidence of germline BRCA1/2 PVs were detected in Period 2 (17.2%) and Period 3 (18.5%). Uptake of cascade testing from first-degree relatives was significantly lower in those women undergoing mainstream testing compared with those tested in regional genetics clinics (31.6% versus 47.3%, P=0.038). Mainstream testing allows timely detection of germline BRCA1/2 status to select patients for PARP inhibitors, but shortfalls in the uptake of cascade testing in first73 degree relatives requires optimisation to broaden benefits within families.