Abstract PS7-83: Outcomes and risk factors associated with breast cancer in women aged 35 and under: Single centre retrospective analysis
Authors: Dodkins Joanna , Harvey-Jones Elizabeth , Sengupta Sameer , Timbres Jasmine , Swampillai Angela , Sawyer Elinor 
Published: February 2021

Abstract
Introduction Breast cancer is the most common malignancy affecting women under the age of 35 and young age at diagnosis is associated with a poor prognosis. Previous studies have shown that these patients have adverse tumour biology including high grade morphology, lymph node involvement and lack of hormone receptor expression. The aim of this study was to assess the outcomes and risk factors associated with the different subtypes of breast cancer as defined by receptor status in a cohort of young patients in a central London cancer centre. Methods Women diagnosed with breast cancer at the age of 35 or younger between 1st January 2010 and 1st June 2020, at Guys and St Thomas’ NHS Foundation Trust (GSTT) were identified from the GSTT Breast Cancer Clinical Database. Data on patient demographics, histopathology, treatment, family history of breast or ovarian cancer, recent use of oral contraceptive pill (OCP) and outcome were collected from electronic hospital records. Risk factor data was analysed using chi-squared (χ2) statistical analysis; survival data (Overall survival (OS) and recurrence free survival (RFS)) was assessed using cox-regression analysis and formulation of Kaplan-Meier curves. Results We identified 119 patients with a median age of 32.5 years (range 22-35 years). Four were diagnosed with in situ carcinoma (3 DCIS, 1 LCIS) and the remainder were invasive cancers. Of the invasive cancers, 54% (n= 62) were ER+HER2-, 23% (n=26) ER-HER2-, 19% (n=22) ER+HER2+ and 4% (n=5) ER-HER2+. The majority of patients presented with stage 1 or 2 disease and a small number presented with metastatic disease, irrespective of subtype. Approximately 23% (n= 28) of patients had taken the OCP and 15% (n=18) of patients were pregnant or breast feeding at the time of diagnosis, with no variation by subtype. ER+HER2+ patients were less likely to have had children (p=0.0008). ER+HER2- patients were more likely than ER-HER2- patients to have a family history of breast cancer (P=0.03), but were less likely to be referred for genetic testing (52% (n=38) vs 81% (n=21)). 11.8% (n=14) were found to have a germline mutation, two occurred with in situ cancer (BRCA2 in the case of LCIS and TP53 in a case of ER+HER2+ DCIS). Of the ER+HER2- cases that underwent genetic testing 12.5% (n=4) had a germline mutation (2 BRCA2, 1 PALB2, 1 CHEK2) and 38% (n=8) of the ER-HER2-subgroup (6 BRCA1, 2 BRCA2). With a median follow up of 29 months (range 3.1 to 103.3 months), 23% of ER-HER2-, 10% of ER+HER2- and no HER2+ cases had developed a recurrence (loco-regional or distant). 5-year RFS in ER+HER2- was 79.5% vs. 61.9% in ER-HER2- (HR 2.96, 95%CI 0.95-9.20; p=0.061). Of the ER+HER2- patients that recurred, 83% (n=5) had full ovarian function suppression (OFS) with Goserelin. Mean survival was 36.4 months; 12 out of 115 patients died, the 5-year OS across all subgroups was 76.7%. ER-HER2- patients were more likely to have died (27% (n=7) (HR 5.9 95%CI 1.69-20.46; p=0.005), with a 5-year OS of only 47%. Only 6% (n=4) of ER+HER2- patients died, they had a 5-year OS of 89.3%. Only 5% (n=1) of ER+HER2+ patients died (HR 1.47 95%CI 0.16-13.80; p=0.733) with a 5-year OS of 75%. Conclusions Despite optimum treatment, 23% of women under 35 with ER-HER2- breast cancer still died from their disease. In addition, even with this relatively short follow up, there is a subgroup of ER+HER2- patients who presented with a low nodal burden, were treated with full OFS and still recurred. This group of patients would benefit from somatic molecular testing to identify potential treatment targets. The majority of HER2+ patients in this cohort also had ER+ disease which is similar to previous reports of HER2+ breast cancer in young women. However contrary to that report, HER2+ positive patients in our study had a low risk of recurrence, this is likely due to the widespread use of targeted anti-HER2 therapy.
Citation Format: Joanna Dodkins, Elizabeth Harvey-Jones, Sameer Sengupta, Jasmine Timbres, Angela Swampillai, Elinor Sawyer. Outcomes and risk factors associated with breast cancer in women aged 35 and under: Single centre retrospective analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-83.