A population-based cohort of young women diagnosed with breast cancer in Geneva, Switzerland

Purpose Breast cancer is the most frequently diagnosed cancer among women worldwide. Despite the fact that breast cancer is more frequent after fifty years of age, breast cancer among young women has recently drawn particular attention due to an increase in incidence in several western countries. With the exception of individuals with a high genetic risk, breast cancer occurring in younger women remains poorly understood. This project aims at investigating the patient, tumour and treatment characteristics as well as the long-term health outcomes of these women by evaluating numerous variables that were collected from their pathology and medical files, including the social environment, family history, fertility and pregnancy. Participants We constituted a population-based cohort from the Geneva Cancer Registry of 1586 patients with breast cancer who were aged less than 46 years at the time of diagnosis. Findings to date Breast cancer was diagnosed before the age of 35 years in 225 women (14.2%), between 35 and 39 years of age in 368 women (23.2%) and between 40 and 45 years of age in 993 women (62.6%). Most of the patients were diagnosed with luminal A or luminal B molecular subtypes (32.8 and 37.5%, respectively), stage I or II tumours (75.2%), and estrogen (74.8%) and progesterone (67.5%) positive receptors. During the study period, 16.7% of these women developed loco-regional recurrences and 25.4% developed distant metastases; the majority (66.3%) did not have a recurrence. Regarding mortality, 474 (29.9%) women died during the study period, 347 (73.2%) from breast cancer. Future plans The results of this study will help filling the knowledge gap about treatment of young breast cancer patients and having a child after breast cancer, and will provide clinicians and public health professionals’ with additional information to improve quality of care and decrease the impact of breast cancer in young women.