The variety and clinical characteristics of BRCA1/2 and non-BRCA1/2 mutations in women with a suspicion of HBOC before the implementation of multi-gene panels in our referral population was unknown.
This is an exploratory study of all consecutive women tested at the HBOC Unit between 2016-2018. TruSight Cancer panel (Illumina) was used and 16 genes were analyzed: BRCA1, BRCA2, PALB2, ATM, CDH1, CHEK2, TP53, NBN, PTEN, STK11, BRIP1, MLH1, MSH2, MSH6, RAD51D and RAD51C. The main objective was to determine the prevalence of pathogenic mutations (PM) and variants of uncertain significance (VUS). Other secondary objectives were explored such as the distribution of the breast cancer (BC) subtypes and the pathological complete response (pCR) rates following neoadjuvant anthracycline/taxane-based chemotherapy in BRCA1/BRCA2/PALB2-PM BC.
451 women were tested. PM and a VUS were found in 60 (12.7%) and 42 (8.9%) patients, respectively. Among PM cases, 37 (62%) had BC and 23 (38%) had OC. The PMs identified in BC were BRCA2 (35.1%), BRCA1 (21.6%), PALB2 (24.3%), TP53 (8.1%), ATM (5.4%), BRIP1 (2.7%) and PTEN (2.7%). All women with PALB2 PM had BC. Within BRCA2-PM BC, the most common subtype was Luminal B (54%), followed by triple-negative (23%), Luminal A (15%) and HER2-positive (8%). Within cases with BRCA1-PM BC, the most common subtype was triple-negative (88%) followed by Luminal B (12%). Within cases with PALB2-PM BC, the most common subtype was Luminal B (56%), followed triple-negative (33%) and Luminal A (11%). Interestingly, within patients BRCA1/BRCA2/PALB2-PM BC (n = 30), only 1 (3.3%) case had HER2+ BC. Following neoadjuvant chemotherapy, 11 of 17 (58%) cases with BRCA1/BRCA2/PALB2-PM BC achieved a pCR. Within cases with OC, PM identified were BRCA2 (39.1%), BRCA1 (39.1%), TP53 (4.3%), BRIP1 (4.3%), CHEK2 (4.3%), RAD51D (4.3%) and MSH6 (4.3%).
Our in-house clinical guidelines detect >10% of tested cases with HBOC. Non-BRCA1/2 PM are found in 35% of the cases. BRCA1/BRCA2/PALB2-PM BC is associated with aggressive tumor biology and high chemotherapy sensitivity.
Hospital Clinic of Barcelona.
Has not received any funding.
A. Prat: Advisory role/lecture fees: NanoString Technologies, Roche, Pfizer, MSD, Novartis, Lilly; Funding: NanoString Technologies, Novartis; Scientific advisory role: Oncolytics Biotech. All other authors have declared no conflicts of interest.