Assessment of HER-2 status in invasive breast cancer in Brazil

To characterize the frequency of HER-2-positive breast cancer in Brazil.

In this prospective observational study, we first ascertained the HER-2 status of invasive breast cancer specimens by automated immunohistochemistry (IHC). For specimens classified as 2+ by IHC, we performed in situ hybridization (ISH).

From February, 2011 to December, 2012, 1,495 breast specimens were registered, and 1,310 samples collected at 24 centers were analyzed. Median patient age was 54 years, and the majority of samples were obtained from segmental (46.9%) or radical mastectomy (34.4%). The predominant histological type was invasive breast carcinoma of no special type (85%), 64.3% had tubule formation (grade 3), and estrogen/progesterone receptors (ER/PR) were positive in 77.4/67.8% of the specimens analyzed, respectively. Using IHC, we found a negative HER-2 status (0 or 1+) in 72.2% of specimens, and 3+ in 18.5%; the 9.3% scored as 2+ were further analyzed by ISH, of which 15.7% were positive (thus, 20.0% of samples were HER-2- -positive by either method). We found no association between HER-2 scores and menopausal status or histological type. Tumors classified as 3+ came from younger patients, and had higher histological grade and less frequent expression of ER/PR. In the North region of Brazil, 34.7% of samples were 3+, with lower frequencies in the other four regions of the country.

Our findings provide estimates for the frequency of HER-2 positivity in Brazil and raise the hypothesis that biological differences may underlie the different distribution of breast-cancer phenotypes among different Brazilian regions.