ESR1 and cancer: However, RRSO, even among women with average risk, reduces OC risk by 96% to 97%.36 It is likely that OC risk reduction for non-BRCA CSG PV carriers and BC risk reduction for PALB2 PV carriers would be similar to levels obtained for BRCA. The estrogen receptor status of PALB2-altered BC is similar to BRCA2, and most cancers have high-grade histology.