Exploring the Role of Breast Density on Cancer Prognosis among Women Attending Population-Based Screening Programmes

Abstract

CAMISS Study Group (in alphabetical order): IMIM (Hospital del Mar Medical Research Institute), Barcelona: Xavier Castells, Merce` Comas, Laia Domingo, Francesc Macia`, Marta Roman, Anabel Romero, Maria Sala; Canary Islands Health Service: Teresa Barata, Isabel Diez de la Lastra, Mariola de la Vega; Corporacio´ Sanitaria Parc Taul´ı, Sabadell: Marisa Bare´, Nu´ria Tora`; Hospital Santa Caterina, Girona: Joana Ferrer; Epidemiology Unit and Girona Cancer Registry: Maria Carmen Carmona-Garcia; Hospital GaldakaoUsansolo, Vizcaya: Susana Garc´ıa, Maximina Mart´ın, Miren Orive, Maria Amparo Valverde; Canary Islands Foundation for Health Research: Jeanette Pe´rez, Amado Rivero, Cristina Valca´rcel; Hospital Costa del Sol, University of Ma´laga: Mar´ıa del Carmen Padilla, Maximino Redondo, Teresa Te´llez, Irene Zarcos; Hospital Universitario Donostia/Biodonostia: Cristina Churruca, Amaia Perales, Javier Recio, Irune Ruiz, Cristina Sarasqueta, Jose Mar´ıa Urraca; Instituto Oncolo´gico de Guipu´zcoa-Onkologikoa: Maria Jesu´s Michelena; Hospital Universitario Basurto: Julio Moreno; Hospital Universitario Cruces: Gaizka Mallabiabarrena, Patricia Cobos, Borja Otero; Hospital Universitario Txagorritxu: Javier Gorostiaga, Itsaso Troya

Background. Our aim was to assess the role of breast density on breast cancer mortality and recurrences, considering patient and tumour characteristics and the treatments received among women attending population-based screening programmes. Methods. We conducted a retrospective cohort study among women aged 50–69 years attending population-based screening programmes, diagnosed with invasive breast cancer between 2000 and 2009, and followed up to 2014. Breast density was categorised as low density (≤25% dense tissue), intermediate density (25–50%), and high density (≥50%). Cox proportional hazards regression models were fitted to estimate the adjusted hazard ratios (aHR) and 95% confidence intervals (95% CI) for death and recurrences, adjusting by patient characteristics, mode of detection (screen-detected vs. interval cancer), and tumour features. Results. The percentage of deaths and recurrences was higher among women with intermediate- and high-density breasts than among women with low-density breasts ( for death; for recurrences). Adjusted Cox proportional hazards regression models revealed that women with intermediate- and high-density breasts had a higher risk of death than women with low-density breasts, being statistically significant for intermediate densities (aHR = 2.19 [95% CI: 1.16–4.13], aHR = 1.44 [95% CI: 0.67–3.1], respectively). No association was found between breast density and recurrences. Conclusions. Breast density was associated with a higher risk of death, but not of recurrences, among women participating in breast cancer screening. These findings reinforce the need to improve screening sensitivity among women with dense breasts and to routinely assess breast density, not only for its role as a risk factor for breast cancer but also for its potential influence on cancer prognosis

*is study was supported by grants from Instituto de Salud Carlos III FEDER (grant numbers: PS09/01153, PI12/00387, PI11/01296, PI15/ 00098, and PI16/00244) and by the Research Network on Health Services in Chronic Diseases (Instituto de Salud Carlos III) (REDISSEC: RD12/0001/0015, RD12/0001/ 0007, and RD16/0001/0013)