Poster display session: Breast cancer - early stage, locally advanced & metastatic, CNS tumours, Developmental therapeutics, Genitourinary tumours - prostate & non-prostate, Palliative care, Psycho-oncology, Public health policy, Sarcoma, Supportive care Poster Display session

237P - Index BRCA1/2 testing under a multidisciplinary program

Presentation Number
237P
Lecture Time
12:45 - 12:45
Speakers
  • Duarte H. Machado (Lisbon, PT)
Location
Hall A3 - Poster Area Networking Hub, ICM M√ľnchen, Munich, Germany
Date
22.10.2018
Time
12:45 - 13:45

Abstract

Background

Germline BRCA1/2 mutations are the main cause of Hereditary Breast and Ovarian Cancer syndrome (HBOC). Whenever possible, Index testing should be done in a family member with a previous breast or ovarian cancer (affected individuals, AI) and not in non-affected individuals (NAI). In here we review the characteristics, decisional process and BRCA1/2 mutation detection rate of index testing in AI and NAI.

Methods

Analysis of all consecutive HBOC files registered from November 2000-December 2017. The BRCAPRO model was applied to affected patients (pts) and the Tyrer-Cuzick model to all non-affected female individuals. Comprehensive BRCA1/2 analysis was done, including MLPA and c.156_157insAlu testing (Machado PM et al., 2007)

Results

6112 individuals were counseled and 4642 (76%) consented on genetic BRCA1/2 testing: 3420 (56%) index pts and 1222 (20%) family relatives. Index pts: 3361 (98.3%) had a previous cancer diagnosis (AI) and 59 were NAI. Both groups included mostly women (AI-95.2%; NAI-97%). The mean age for NAI was 40.7 years (20-79) and 79% had at least one-first degree relative with breast or ovarian cancer. Testing decision for NAI: either affected relatives were dead (80%), refused testing (15%) or were unreachable (5%). The global BRCA1/2 detection rate for index pts was 10.44%, being higher (13.6%) for NAI index cases (8 pathogenic variants: 2 BRCA1, 6 BRCA2). The mean pretest BRCA mutation probability (P) for NAI was 10.72% (range 0.06-42.8). This P was 18,5% for those who tested positive and 9,45% for inconclusive results ( p > 0.05). The pre-test lifetime breast cancer risk was 26.69% for all NA cases, being higher for those found to be BRCA1/2 carriers (36.07% vs 28.04%).

Conclusions

Our conservative approach allowed for a detection rate in NAI that compared favorably to affected index pts. Although some groups propose widespread BRCA1/2 screening we suggest that NAI should be tested as index only if no cancer relatives are available. Despite the small sample size, the BRCA pre-test probability of 10% or higher seems to increase the detection rate in this subgroup.

Legal entity responsible for the study

Fátima Vaz.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.

Collapse