Genetic testing in a cohort of young patients with HER2-amplified breast cancer.

BACKGROUND: Young age at diagnosis for breast cancer raises the question of genetic susceptibility. We explored breast cancer susceptibility genes testing on ≤40-year-old patients with HER2-amplified invasive breast cancer. PATIENTS AND METHODS: Patients were selected from a large UK cohort study. The inclusion criterion was age ≤40 at diagnosis with confirmed HER2-amplified breast cancer. The probability of finding a BRCA gene mutation was calculated based on family history. Genetic testing used was either clinical testing for BRCA1 and BRCA2, with a subset also tested for TP53 mutations, or research-based testing using a typical panel comprising 17 breast cancer susceptibility genes (CSGs) including BRCA1, BRCA2 and TP53. RESULTS: Of the 591 eligible patients, clinical testing results were available for 133 cases and an additional 263 cases had panel testing results. BRCA testing across 396 cases found 8 BRCA2 (2%) and 6 BRCA1 (2%) pathogenic mutations. Of the 304 patients tested for TP53 mutations, overall 9 (3%) had deleterious TP53 mutations. Of the 396 patients, 101 (26%) met clinical criteria for BRCA testing (≥10% probability), among whom 11% had pathogenic BRCA mutations (6 BRCA2, 5 BRCA1). Where the probability was calculated to be <10%, only 4 of 295 (1%) patients had BRCA mutations. Among the 59 patients who had TP53 testing meeting the 10% threshold, 7 had mutations (12%). Likely functionally deleterious mutations in 14 lower penetrance CSGs were present in 12 of 263 (5%) panel-tested patients. CONCLUSION: Patients aged <41 at diagnosis with HER2+ breast cancer and no family history of breast cancer can be reassured that they have a low chance of being a high-risk gene carrier. If there is a strong family history, not only BRCA but also TP53 gene testing should be considered. The clinical utility of testing lower penetrance CSGs remains unclear.

Family history and outcome of young patients with breast cancer in the UK (POSH study).

BACKGROUND: Young patients presenting to surgical clinics with breast cancer are usually aware of their family history and frequently believe that a positive family history may adversely affect their prognosis. Tumour pathology and outcomes were compared in young British patients with breast cancer with and without a family history of breast cancer. METHODS: Prospective Outcomes in Sporadic versus Hereditary breast cancer (POSH) is a large prospective cohort study of women aged less than 41 years with breast cancer diagnosed and treated in the UK using modern oncological management. Personal characteristics, tumour pathology, treatment and family history of breast/ovarian cancer were recorded. Follow-up data were collected annually. RESULTS: Family history data were available for 2850 patients. No family history was reported by 65·9 per cent, and 34·1 per cent reported breast/ovarian cancer in at least one first- or second-degree relative. Patients with a family history were more likely to have grade 3 tumours (63·3 versus 58·9 per cent) and less likely to have human epidermal growth factor receptor 2-positive tumours (24·7 versus 28·8 per cent) than those with no family history. In multivariable analyses, there were no significant differences in distant disease-free intervals for patients with versus those without a family history, either for the whole cohort (hazard ratio (HR) 0·89, 95 per cent c.i. 0·76 to 1·03; P = 0·120) or when stratified by oestrogen receptor (ER) status (ER-negative: HR 0·80, 0·62 to 1·04, P = 0·101; ER-positive: HR 0·95, 0·78 to 1·15, P = 0·589). CONCLUSION: Young British patients presenting to breast surgical clinics with a positive family history can be reassured that this is not a significant independent risk factor for breast cancer outcome.