Reproductive factors and risk of breast cancer by tumor subtypes among Ghanaian women: A population‐based case–control study. Issue 6 (13th March 2020)

• Record Type: Journal Article
• Authors: Figueroa, Jonine D.; Davis Lynn, Brittny C.; Edusei, Lawrence; Titiloye, Nicholas; Adjei, Ernest; Clegg‐Lamptey, Joe‐Nat; Yarney, Joel; Wiafe‐Addai, Beatrice; Awuah, Baffour; Duggan, Maire A.; Wiafe, Seth; Nyarko, Kofi; Aitpillah, Francis; Ansong, Daniel; Hewitt, Stephen M.; Ahearn, Thomas; Garcia‐Closas, Montserrat; Brinton, Louise A.
• Is Part Of: International journal of cancer. Volume 147:Issue 6(2020)
• Page Start: 1535
• Page End: 1547
• Publication Date: 2020-03-13
• Subjects: reproductive risk factors -- subtype heterogeneity -- racial disparities -- breast cancer; Cancer -- Periodicals; Cancer -- Prevention -- Periodicals; 616.994
• DOI: 10.1002/ijc.32929
• Languages: English
• ISSNs: 0020-7136

Abstract

Abstract : Higher proportions of early‐onset and estrogen receptor (ER) negative cancers are observed in women of African ancestry than in women of European ancestry. Differences in risk factor distributions and associations by age at diagnosis and ER status may explain this disparity. We analyzed data from 1, 126 cases (aged 18–74 years) with invasive breast cancer and 2, 106 controls recruited from a population‐based case–control study in Ghana. Odds ratios (OR) and 95% confidence intervals (CI) were estimated for menstrual and reproductive factors using polytomous logistic regression models adjusted for potential confounders. Among controls, medians for age at menarche, parity, age at first birth, and breastfeeding/pregnancy were 15 years, 4 births, 20 years and 18 months, respectively. For women ≥50 years, parity and extended breastfeeding were associated with decreased risks: >5 births vs . nulliparous, OR 0.40 (95% CI 0.20–0.83) and 0.71 (95% CI 0.51–0.98) for ≥19 vs . <13 breastfeeding months/pregnancy, which did not differ by ER. In contrast, for earlier onset cases (<50 years) parity was associated with increased risk for ER‐negative tumors ( p ‐heterogeneity by ER = 0.02), which was offset by extended breastfeeding. Similar associations were observed by intrinsic‐like subtypes. Less consistent relationships were observed with ages at menarche and first birth. Reproductive risk factor distributions are different from European populations but exhibited etiologic heterogeneity by age at diagnosis and ER status similar to other populations. Differences in reproductive patterns and subtype heterogeneity are consistent with racial disparities in subtype distributions. Abstract : What's new? Breast‐cancer risks differ between women of African ancestry and women of European ancestry, especially for aggressive, hormone‐negative tumors. In this large African study, the authors found that, while increased parity reduced the risk of all breast‐cancer subtypes after age 50, the opposite was true for risk of developing estrogen‐receptor (ER) negative tumors at a younger age. However, longer breastfeeding appeared to reduce the risk both for early‐onset, ER‐negative tumors and for all tumor subtypes with later onset. Efforts to promote extended breastfeeding may thus help reduce many breast cancers in this population.