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Reproductive factors and risk of breast cancer by tumor subtypes among Ghanaian women: A population‐based case–control study
Author(s) -
Figueroa Jonine D.,
Davis Lynn Brittny C.,
Edusei Lawrence,
Titiloye Nicholas,
Adjei Ernest,
CleggLamptey JoeNat,
Yarney Joel,
WiafeAddai Beatrice,
Awuah Baffour,
Duggan Maire A.,
Wiafe Seth,
Nyarko Kofi,
Aitpillah Francis,
Ansong Daniel,
Hewitt Stephen M.,
Ahearn Thomas,
GarciaClosas Montserrat,
Brinton Louise A.
Publication year - 2020
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.32929
Subject(s) - menarche , medicine , breastfeeding , odds ratio , parity (physics) , demography , population , breast cancer , case control study , pregnancy , obstetrics , risk factor , logistic regression , gynecology , confounding , cancer , pediatrics , biology , genetics , environmental health , physics , particle physics , sociology
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.