Abstract PO3-02-09: Breast cancer in women under the age of 40 years.A south Wales UK reflection on incidence, tumour biology and outcomes over 10 years

Abstract Introduction: The incidence of breast cancer in the under 40-year-old age group is approximately 7% (Anders et al., 2009). Studies suggests that the management of Breast cancer in adolescent and young women is more challenging, with this age group under-represented in clinical trials. We investigated the management and outcomes of a cohort of 98 patients seen between 2013 and 2023 in the Hywel Dda NHS University Health Board, Wales, UK. Methods: A retrospective review was performed. Demographic, surgical and outcome data for patients under the age of 40 years was collated and analysed. Results: The cohort size was 98, representing 2.45% of the breast cancer population treated in the Health Board during this timeframe. The age of the cohort ranged from 23 years to 40 years, 12 out of 98 (12.24%) were under 30 years. Mean age was 35.28 years. Unfortunately, 8.16% (8/98) of the cohort died between 12 months to 96 months. Two patients were lost to follow up. Tumour biology results confirmed that most of the cohort had invasive ductal carcinoma (IDC), with 13.27% Grade 1, 37.76 % Grade 2 and 40.82% Grade 3. There were 4 (4.08%) invasive lobular carcinomas (ILC) in the cohort, 2 Grade 2 and 2 Grade 3. The remaining tumour groups were, 1 case of DCIS (Grade-2 intermediate grade), Grade-1 mucinous carcinoma, 1 Grade-1 ductal-lobular breast cancer and 1 medullary carcinoma. 10.20% of the cohort had triple negative cancers (ER, PR, Her-2 negative) and 10.20% were ER, PR, HER2 positive Triple positive. 40.82% metastatic axillary lymph nodes involvement on histology either on presentation or following sentinel node biopsy. Operative details confirmed that the 51.02% (50/98) of the cohort underwent mastectomy. 10 out of those 50 patients underwent contralateral risk reducing mastectomy .46 patients had breast conservation surgery. One patient is awaiting surgery, the other has been diagnosed with metastatic breast cancer at diagnosis. Patients received both neoadjuvant and adjuvant chemotherapy depending on initial assessment and MDT discussion ACP, FEC, Taxane and platinum-based chemotherapy, Anti Her-2. NAC was provided for all HER-2+ patients. Endocrine treatment and ovarian function suppression, and adjuvant Radiotherapy was also given. Some patients had a complete pathological response to NAC; however, some did not respond well. In addition, 10.20% of the cohort underwent bilateral salpingo-oophorectomy during their treatment and follow up. Genetic assessment confirmed that 3/98 (3.06%) of the cohort were BRCA2 positive, one BRCA1 carrier, 2 patients were BRCA negative, two have been referred for genetics assessment and two still awaiting consultation with genetics. In one patient somatic mutation was found in PTEN, BIRC3, HRAS, TP53, PMS, (5 gene panel). In one patient, panel was reassuring. PALB-2, TP53 was also reassuring in one patient. One patient who passed away at the age of 34 did not have any alteration in 5 gene panel. Three patients developed other malignancies during the 10-year period: 1 uterine, 1 cervix, 1 papillary thyroid cancer. 6/98 (6.12%) developed metastatic disease and one developed a local recurrence. One patient developed metastasis while pregnant, and by contrast one patient gave birth to a baby after stopping her endocrine treatment. One patient who passed away had no response to neoadjuvant chemotherapy (NAC). Discussion: The results from the cohort confirm that the incidence of TNBC and triple positive cancers is like that found in the general breast cancer population (10-15%). Our engagement with the genetics team has increased since the initial 2013 cohort. There is now an established system for referrals for young women with breast cancer. It is probably not surprising that other primary invasive cancers were found, whilst on follow up. Citation Format: Sohail Khan, Saira Khawaja, Yousef Sharaiha, Asma Munir, Anita Huws. Breast cancer in women under the age of 40 years.A south Wales UK reflection on incidence, tumour biology and outcomes over 10 years abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-02-09.