BRCA1 and triple-negative breast carcinoma: In a patient with a somatic BRCA1 triple-negative breast cancer treated with two prior regimens of olaparib (monotherapy and in combination with the WEE1 inhibitor adavosertib), a BRCA1 alteration and multiple polyclonal reversions in BRCA1 were detected at baseline, consistent with the existence of independent clones driving resistance to previous DDR-directed therapy22.