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Breast cancer subtypes in Chinese Americans: A study from the Mount Sinai Health System.

39 Background: Breast cancer has been increasing in many Asian countries, as well as among Asian Americans. While many studies have examined breast cancer subtypes in African American and Caucasian populations, few have looked at tumor subtypes in the Asian population. We aimed to examine breast cancer subtypes in Chinese Americans.


METHODS
We identified all Chinese patients diagnosed with invasive breast cancers between 2005 and 2012 from the Cancer Registry of Mount Sinai Beth Israel, Mount Sinai St. Luke's, and Roosevelt Hospitals. The following clinical data were collected for each patient: age at diagnosis, year of diagnosis, largest tumor size (cm), lymph node status, estrogen receptor (ER), progesterone receptor (PR) and HER2 status. Based on ER, PR, and HER2, patients were categorized into three molecular subtypes: 1) Hormone receptor (HR)+ (ER and/or PR positive, HER2 negative), HER2+ and triple negative (TN) (ER, PR, and HER2 negative). Descriptive variables were analyzed using one-way Anova test. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated from logistic regression models.


RESULTS
There were 175 Chinese patients diagnosed with invasive breast cancers from 2005 to 2012. Median age at diagnosis was 54 (range 27-90). One hundred fourteen (65%) were HR+, 41 (23%) were HER2+, and 20 (11%) were TN. There were 59 (34%) patients diagnosed at age ≤ 50 and twelve patients (7%) were diagnosed at age < 40. There were more HER2+ and TN breast cancers diagnosed in women age ≤ 50 compared to age > 50, but the difference was not statistically significant. Women in the HR+ group were diagnosed at an older age compared to the other two subgroups (57 ± 12, 52 ± 8, and 52 ± 10 for HR+, HER2+, and TN, respectively, p = 0.036). Patients with TN breast cancers were more likely to have lymph node involvement compared to HR+ or HER2+ patients (p = 0.02). There was a trend of increasing prevalence of HER2+ breast cancer observed in recent years: 18.5% in 2005-2006, 23.8% in 2007-2008, 18.4% in 2009-2010, and 29.8% in 2011-2012.


CONCLUSIONS
We observed a high proportion of breast cancer among young Chinese Americans as well as an increasing prevalence of HER2+ breast cancer in this population in recent years. Further studies are warranted.