Reproductive Risk Factors for Female Breast Cancer: A Case – Control Study

Abstract

Background:  Breast cancer is the most common female cancer in Pakistan. Its incidence in Pakistan is 2.5 times higher than that in neighboring countries like Iran and India. Association of reproductive factors with breast cancer is unclear in our population.

Objectives:  To find out the association of reproductive factors like parity, age at first live birth and lactation with breast cancer.

Design, Setting and Participants:  It was a case-control study comprising 150 breast cancer patients and 300 control subjects. The study was done in Mayo Hospital Lahore between October, 2008 and April, 2009.

Methods:  Both cases and controls were interviewed in wards after taking verbal consent. A short structured questionnaire was used to obtain information regarding basic demographic, menstrual and reproductive characteristics.

Results:  Breast cancer patients and control subjects did not differ regarding age (p = 0.9), early menarche (OR for menarche at < 12 years vs. ≥ 12 = 1.6, 95% CI = 0.6 - 4.3), and late menopause (OR for menopause at ≥ 50 vs. < 50 = 1.0, 95% CI = 0.5 - 2.0). History of breast cancer in 1^st degree relatives did not increase breast cancer risk (OR = 1.0, 95% CI = 0.5 - 2.1). Nulliparous women had significantly higher risk than parous women (OR = 4.7, 95% CI = 1.9 - 11.0). Women with younger age at first live birth (< 30 years) had less breast cancer risk as compared to women with ≥ 30 years of age at first live birth (OR = 0.2, 95% CI = 0.1 - 0.5). Breastfeeding had no effect on the risk of breast cancer in parous women.

Conclusion:  Nulliparity and more age at first live birth was associated with increased breast cancer risk. Breastfeeding was not protective against breast cancer.

Keywords:  breast cancer, nulliparity, lactation, risk factors.