EPR19-072: Breast Cancer Laterality and Immunohistochemical Characteristics

Abstract

Background: Differences between left and right breast cancer have been investigated in the past in terms of incidence; it is higher on the left side than on the right. This difference has ranged from 2% to 5%. However, there are no publications looking at differences in immunohistochemical characteristics between left and right sided breast cancer. This study aims to assess the incidence and age distribution as well as the following immunohistochemical characteristics: estrogen receptor (ER), progesterone receptor (PR), and epidermal growth factor 2 (HER-2). We compared the age distribution to U.S. population as well as other Arab populations. In addition we compared these and other characteristics with respect to the laterality of the breast cancer. Methods: In this pilot retrospective descriptive study, data was collected anonymously on 300 patients who presented to the Saint George Hospital University Medical Center in Beirut. They were extracted from the inpatient files with a diagnosis of breast cancer in order of presentation from 2012 until the total number of files was reached. The measured parameters included the sex of the patient, the age at diagnosis, breast cancer laterality and stage, the need for surgical treatment, and ER status, PR status, and HER-2 status as shown on the official biopsy results of the cases studied. Results: HER-2, PR-, and ER-positive receptors were found to be more frequent by 4%, 9%, and 1% on the left side as compared with the right side, respectively. These numerical differences, however, were not statistically significant. Moreover, our data analysis shows that the Lebanese population distribution of breast cancer is skewed towards a younger age when compared to the U.S., with a median age of diagnosis of 53 and 62, respectively. Finally, in term of incidence, there was a 12% increase in incidence of left side breast cancer over the right side but this value did not reach statistical significance. Conclusions: This is the first study to show the relationship between hormonal receptors and laterality of breast cancer. We concluded that there is a trend towards statistically significant differences between laterality immunohistochemical characteristics. Epidemiological relationships between the Lebanese population, the Arab population, and the U.S. population were discussed. Further researches on larger population may be needed to show some of the trends presented in this article to be statistically significant.