Reproductive factors and risk of breast carcinoma in a study of white and African‐American women

Abstract

BACKGROUNDFew studies have investigated the association between reproductive factors and the risk of breast carcinoma among African‐American women. The authors assessed whether the number of full‐term pregnancies, age at first full‐term pregnancy, and total duration of breastfeeding were associated with similar relative risk estimates in white and African‐American women in a large multicenter, population‐based case–control study of breast carcinoma.METHODSCase patients were 4567 women (2950 white women and 1617 African‐American women) ages 35–64 years with newly diagnosed invasive breast carcinoma between 1994 and 1998. Control patients were 4668 women (3012 white women and 1656 African‐American women) who were identified by random‐digit dialing and were frequency matched to case patients according to study center, race, and age. Adjusted odds ratios and 95% confidence intervals were estimated using unconditional logistic regression.RESULTSFor white women, the reduction in risk of breast carcinoma per full‐term pregnancy was 13% among younger women (ages 35–49 years) and 10% among older women (ages 50–64 years). The corresponding risk reductions for African‐American women were 10% and 6%, respectively. Risk decreased significantly with increasing number of full‐term pregnancies for both races and both age categories. Duration of lactation was inversely associated with breast carcinoma risk among younger parous white (trend P = 0.0001) and African‐American (trend P = 0.01) women. African‐American women tended to have more children compared with white women, but parity rates were lower in younger women than in older women in both racial groups. However, breastfeeding was substantially more common in young white women than in young African‐American women.CONCLUSIONSOverall, parity and lactation had similar effects on breast carcinoma risk in white and African‐American women. If younger African‐American women now are giving birth to fewer children than in the past, without a substantial increase in breastfeeding, breast carcinoma rates may continue to increase at a more rapid rate among these women compared with white women. Cancer 2004. Published 2004 by the American Cancer Society.

Reproductive factors and subtypes of breast cancer defined by hormone receptor and histology

“…We recently confirmed these findings in the Women's Contraceptive and Reproductive Experiences (CARE) Study and showed that these effects are similar in African-American and White women (Ursin et al, 2004).…”

“…Our recent evaluation of reproductive factors from the CARE study (Ursin et al, 2004) found that the effects of reproductive factors were in general very similar in African-American and White women. In particular, parity and lactation had similar protective effects in the two racial groups.…”

Breast Cancer Epidemiology in Blacks and Whites: Disparities in Incidence, Mortality, Survival Rates and Histology

“…There is some evidence to suggest that, unlike the protective effect of pregnancy on breast cancer risk among women after age 45, early childbearing and higher birth rate observed among black women could increase the likelihood of higher incidence of premenopausal breast cancer [28][29][30] . Moreover, among younger black women, multiparity 31 coupled with lower likelihood of lactation and shorter duration of lactation 32 may also contribute to a higher incidence rate. The reduction in modifiable risk factors including, hormone replace therapy, alcohol consumption, physical activity, and duration of breast-feeding, could substantially reduce breast cancer incidence 33 .…”

Mammary developmental fate and breast cancer risk

“…Reproductive history is the strongest and most consistent risk factor outside of genetic background and age (McPherson et al 2000, Harris et al 1992, Kelsey & Gammon 1991, Althuis et al 2004, Ursin et al 2004. Early menarche, late menopause, parity, and late age of first pregnancy are each independent risk factors.…”