Risk factors for breast cancer in a cohort of mammographic screening program: a nested case–control study within the FRiCaM study

• Published in: Cancer medicine (Malden, MA) Vol. 7; no. 5; pp. 2145 - 2152
• Main Authors: Bravi, Francesca, Decarli, Adriano, Russo, Antonio Giampiero
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01-05-2018; John Wiley and Sons Inc; Wiley
• Subjects: Adipose tissue; Adult; Age Factors; Aged; Body Mass Index; Breast - diagnostic imaging; Breast - pathology; Breast cancer; Breast Density - physiology; Breast Neoplasms - epidemiology; Cancer Prevention; Case-Control Studies; cohort; Cohort Studies; Early Detection of Cancer - methods; Early Detection of Cancer - statistics & numerical data; Female; Health risk assessment; Humans; Italy - epidemiology; Life Style; Mammography; Mammography - statistics & numerical data; Menarche; Menopause; Middle Aged; nested case–control study; Original Research; Pregnancy; prevention; Regression analysis; Reproductive History; Risk Factors; Surveys and Questionnaires; Womens health; Young Adult; Italy; cohort; risk factors; Breast cancer; nested case-control study; prevention
• ISSN: 2045-7634; 2045-7634
• DOI: 10.1002/cam4.1427

Breast cancer is the most common cancer diagnosis and the leading cause of cancer death among women in the world, and differences across populations indicate a role of hormonal, reproductive and lifestyle factors. This study is based on a cohort of 78,050 women invited to undergo a mammogram by Local Health Authority of Milan, between 2003 and 2007. We carried out a nested case–control study including all the 3303 incident breast cancer cases diagnosed up to 2015, and 9909 controls matched by age and year of enrollment. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated using logistic regression models. The ORs were 0.88 (95% CI: 0.78–0.98) for an age at menarche ≥14 years and 1.39 (95% CI: 1.07–1.81) for an age of 30 years or older at first pregnancy. Body mass index (BMI) was positively associated with breast cancer risk in women older than 50 years (OR = 1.89, 95% CI: 1.54–2.31, for BMI≥30 vs. <20), while the association tended to be inverse in younger women. A high mammographic density increased breast cancer risk (OR = 2.61, 95% CI: 2.02–3.38 for density >75% vs. adipose tissue). The ORs were 1.67 (95% CI: 1.47–1.89) and 2.04 (95% CI: 1.38–3.00) for one first‐degree relative and two or more relatives affected by breast cancer, respectively. Our study confirms the role of major recognized risk factors for breast cancer in our population and provides the basis for a stratification of the participants in the mammographic screening according to different levels of risk.
This study is based on a uniquely large Italian cohort of participants of mammographic screening program and investigated several risk factors. Late menarche, and an early age at first pregnancy protected against breast cancer. A higher mammographic density, family history of breast cancer, and a higher body weight (in postmenopause) increased breast cancer risk. Our study provides the basis for a stratification of participants in the mammographic screening according to different levels of risk.