Clinical utility of testing for PALB2 and CHEK2 c.1100delC in breast and ovarian cancer

To investigate the contribution of PALB2 pathogenic gene variants (PGVs, PALB2_PGV) and the CHEK2 c.1100delC (CHEK2_1100delC) PGV to familial breast and ovarian cancer, and PALB2_PGV associated breast cancer pathology. Outcomes of germline PALB2_PGV and CHEK2_1100delC testing were recorded in 3,127 women with histologically confirmed diagnoses of invasive breast cancer, carcinoma in situ, or epithelial nonmucinous ovarian cancer, and 1,567 female controls. Breast cancer pathology was recorded in PALB2_PGV cases from extended families. Thirty-five PALB2 and 44 CHEK2_1100delC PGVs were detected in patients (odds ratio [OR] PALB2 breast–ovarian = 5.90 [95% CI: 1.92–18.36], CHEK2 breast–ovarian = 4.46 [95% CI: 1.86–10.46], PALB2 breast = 6.16 [95% CI: 1.98–19.21], CHEK2 breast = 4.89 [95% CI: 2.01–11.34]). Grade 3 ER-positive HER2-negative, grade 3 and triple negative (TN) tumors were enriched in cases with PALB2 PGVs compared with all breast cancers known to our service (respectively: 15/43, 254/1,843, P = 0.0005; 28/37, 562/1,381, P = 0.0001; 12/43, 204/1,639, P