Abstract Background: In Mexico, it is recognized that breast cancer (BC) is diagnosed at younger ages than that reported in the US and other populations. Although national data is not available regarding BC age of diagnosis distribution, data from the INCAN, the main referral center in Mexico, showed that 17% of the total 893 newly diagnosed BC patients seen in 2012 were younger than 40 years old (which is more than twice that -7%- reported for US BC patients). We conducted a retrospective study in order to describe the frequency of BC among young Mexican BC patients, as well as their pathological characteristics at diagnosis and patters of recurrence. Methods: Clinical and pathologic data from young pts (≤42 years old) who were newly diagnosed with invasive BC between January 2007 and December 2010 at the INCAN in Mexico and were followed for at least 2 years were identified. Clinical stage at diagnosis was recorded and estrogen receptor, progesterone receptor and HER2 expression were determined by immunohistochemistry and/or FISH. Proportion differences were tested using the Chi-square test. Results: 445 young patients were identified from a total of 2919 BC patients (15%). A total of 320 patients met the inclusion criteria for analysis. Median age of diagnosis was 36 years (19-42). 49% of patients were very young patients (≤ 35 years). 19% were diagnosed as early disease, 67.5% as locally advanced BC and 13.5% as metastatic. 32% of patients had triple negative BC disease, while 27% were HER2 positive. From the non-metastatic patients at diagnosis, 31% developed recurrence (65% systemic, 21% loco regional and 14% both). After a median follow-up of 26 months, 18% of the 320 patients died secondary to BC disease progression. Conclusions: Although this series corresponds to patients treated at a reference national center, the data reported in this study suggests that BC among young women is very prevalent in Mexico compared to other populations. The causes underlying the striking difference in age at diagnosis in Mexican BC patients are unknown and have not been investigated, including the genetic contributing factors. As reported in non-Hispanic population studies, BC among young women is diagnosed in more advanced stages, and triple-negative and HER2 positive diseases are more frequent. It is associated with a high proportion of systemic and loco regional recurrence, with a dismal prognosis. Due to the substantial number of BC cases among young women in Mexico, its prospective study is more than justified. In order to meet with this goal, our group is preparing the establishment of the Mexican Young Women's Breast Cancer Cohort Program at the INCAN in Mexico and to launch the related scientific projects related to this plan. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-12-10.
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