RB1 and breast cancer: A comparison of BL and PD tumors revealed significantly increased frequencies of somatic genomic alterations in PD tumors for six BC-associated genes, BRCA1 (p = 0.040), BRCA2 (p = 0.028), ESR1 (p = 0.00043), KMT2C (p = 0.012), PTEN (p = 0.044), and RB1 (p = 0.0005) (Fig. 4a; Additional file 4: Table S4).