Association of use of oral contraceptive pill (OCP) with expression pattern of different molecular subtypes of breast cancer

Abstract

Background: Triple negative breast carcinoma (TNBC) is a breast cancer subtype associated with high mortality and inadequate therapeutic options when compared to non TNBC. Clinical data indirectly suggests where Oral Contraceptive Pill (OCP) usage is high, prevalence of Estrogen Receptor+ (ER+) breast cancer is high and prevalence of TNBC is low. This has lead to our hypothesis that OCP use may increase risk of ER+ breast cancer and OCP use may reduce the risk of TNBC. We aimed at to comparing the prevalence and association of subtypes of breast cancer in OCP users with that of non-users among woman 30 to 60 years of age. Methods: This hospital based observational study of three year duration included 155 subjects of primary invasive breast cancer who got admitted in our institution. The data was obtained for ER, PR, HER2 status, clinical classification and data in relation to demographic factors, reproductive history, and history of OCP use. 155 subjects were divided into two groups. Group-1 included 48 patients with history of OCP use and group-2 included 107 patients who have not used OCP. Data was analysed using SPSS-20. Results: A significant increase in prevalence of molecular subtypes ER+, Progesterone Receptor+ (PR+) and Luminal B breast cancer in OCP users was observed compared to non-users. There was significant decrease in the age at the time of admission in ER+ cancer in OCP users (45.3 years) compared to non-users (52.2years). While age at the time of admission of Basal (TNBC) cancer patients in OCP users (53.1 years) was higher when compared to non-users (45.4years). Upon logistic regression the likelihood of ER+, PR+ and Luminal B in OCP users was 11%,10% and 13% less respectively with 1 year of higher age and the likelihood of TNBC in OCP users was 18% more and 8% less in non-users. Conclusion: OCP use may be associated with increased prevalence of ER+, PR+ and Luminal B breast cancer. On the contrary OCP use is may be associated with delay in the progression of the TNBC.