Abstract
PURPOSE: Breast cancer (BC) in young women is uncommon and tends to present with more aggressive characteristics. To better understand and characterize this scenario in Brazil through real-world data, we performed a subanalysis of AMAZONA III study (ClinicalTrials.gov identifier: NCT02663973). METHODS: The AMAZONA III study (GBECAM 0115) is a prospective registry that included 2,950 women newly diagnosed with invasive BC in Brazil from January 2016 until March 2018 at 22 sites. Valid data were obtained from 2,888 patients regarding age at diagnosis and complete baseline information. To compare epidemiologic and clinicopathological features at the time of diagnosis, patients with BC were divided into two groups according to age: ≤ 40 years and > 40 years. Quantitative variables were described as means, and categorical variables were described as frequencies and percentages and compared using the Pearson's χ(2) test. RESULTS: Of 2,888 women diagnosed with BC, 486 (17%) were ≤ 40 years old. Young women had higher educational level, most were employed and a significant number were married (P < .001 for all associations). Younger patients were more symptomatic at BC diagnosis (P < .001), and they also presented more frequently with stage III, T3/T4, grade 3 tumors, HER-2-positive, luminal B, and triple-negative subtypes. CONCLUSION: Brazilian women younger than age 40 years have unfavorable clinicopathological features of BC at diagnosis, with more aggressive subtypes and advanced stage when compared with older women. These differences are not explained by socioeconomic or ethnic imbalances. The causes of a higher prevalence of BC among young women in Brazil deserve additional investigation.