Menarche, menopause, and breast cancer risk

Abstract

The longer a woman is exposed to cycling reproductive hormones the higher her risk of breast cancer. If she has an early menarche or a late menopause, or both, her risk of breast cancer is increased. Additionally, women who bear children (parous) have a decreased risk of breast cancer compared those without children (nulliparous), 1 Brinton LA Schairer C Hoover RN Fraumeni Jr, JF Menstrual factors and risk of breast cancer. Cancer Invest. 1988; 6: 245-254 Crossref PubMed Scopus (184) Google Scholar , 2 MacMahon B Cole P Lin TM et al. Age at first birth and breast cancer risk. Bull World Health Organ. 1970; 43: 209-221 PubMed Google Scholar purportedly because of the break in reproductive cycling. An understanding of how these reproductive behaviours mediate breast cancer risk will help to establish whether the cumulative length of cycling itself increases breast cancer risk, or whether exposure to the mitogenic effects of oestrogen is more important. This is timely research because women in the 21st century are undergoing menarche earlier, going through menopause later, bearing fewer children, and beginning their families later than ever before. 3 Australian Bureau of StatisticsAustralian Social Trends December 2010. http://www.ausstats.abs.gov.au/Ausstats/subscriber.nsf/0/DE5DE30C9CF6E5E3CA25748E00126A25/$File/41020_2008.pdf Google Scholar Menarche, menopause, and breast cancer risk: individual participant meta-analysis, including 118 964 women with breast cancer from 117 epidemiological studiesThe effects of menarche and menopause on breast cancer risk might not be acting merely by lengthening women's total number of reproductive years. Endogenous ovarian hormones are more relevant for oestrogen receptor-positive disease than for oestrogen receptor-negative disease and for lobular than for ductal tumours. Full-Text PDF Open Access