Mammographic density among indigenous women in forested areas in the state of Amapá, Brazil: a cross-sectional study

ABSTRACT CONTEXT AND OBJECTIVE: There is no register of breast cancer cases among indigenous populations in Brazil. The objective here was to evaluate the association of clinical and demographic characteristics with mammographic density among indigenous women. DESIGN AND SETTING: Cross-sectional analytical study conducted in indigenous territories in the state of Amapá, Brazil. METHODS: Women were recruited from three indigenous territories and underwent bilateral mammography and blood collection for hormonal analysis. They were interviewed with the aid of an interpreter. Mammographic density was calculated using computer assistance, and was expressed as dense or non-dense. RESULTS: A total of 137 indigenous women were included in this study, with an average age of 50.4 years, and an average age at the menarche of 12.8 years. Half (50.3%) of the 137 participants had not reached the menopause at the time of this study. The women had had an average of 8.7 children, and only two had never breastfed. The average body mass index of the population as a whole was 25.1 kg/m2. The mammographic evaluation showed that 82% of women had non-dense breasts. The clinical characteristics associated with mammographic density were age (P = 0.0001), follicle-stimulating hormone (FSH) (P < 0.001) and estrogen levels (P < 0.01). CONCLUSIONS: The majority of the indigenous women had non-dense breasts. Age, menopausal status and FSH and estrogen levels were associated with mammographic density.

背景与研究目的：巴西原住民群体尚无乳腺癌病例登记系统。本研究旨在探讨原住民女性的临床与人口学特征与乳腺钼靶密度（mammographic density）的关联。
研究设计与研究地点：本研究为横断面分析研究，实施地点为巴西阿马帕州的原住民领地。
研究方法：研究人员从三处原住民领地招募女性受试者，为其进行双侧乳腺钼靶检查，并采集血液样本用于激素分析；研究人员借助翻译人员完成受试者访谈。乳腺钼靶密度通过计算机辅助计算得出，分为致密型与非致密型两类。
研究结果：本研究共纳入137名原住民女性，受试者平均年龄为50.4岁，平均初潮年龄为12.8岁；其中50.3%的受试者在研究开展时尚未绝经。受试者平均生育8.7名子女，仅2人从未进行母乳喂养。全体受试者的平均体质量指数为25.1 kg/m²。乳腺钼靶评估结果显示，82%的受试者乳腺为非致密型。与乳腺钼靶密度相关的临床特征包括年龄（P=0.0001）、卵泡刺激素（follicle-stimulating hormone, FSH）（P < 0.001）与雌激素水平（P < 0.01）。
研究结论：大部分原住民女性的乳腺为非致密型；年龄、绝经状态以及卵泡刺激素与雌激素水平均与乳腺钼靶密度存在关联。