Sequencing core HR pathway genes in 12 pairs of pre-treatment and post-progression tumour biopsy samples collected from ovarian cancer patients treated with rucaparib, Kondrashova and colleagues [55] identified a truncation mutation in BRCA1, RAD51C, or RAD51D in 6 of 12 pre-treatment biopsies and one or more secondary mutations that restored the open reading frame in 5 of 6 paired post-progression biopsies; four distinct secondary mutations were observed for RAD51C. Here, BRCA1 is linked to ovarian cancer.