Rethinking hormonal contraception in breast cancer survivors

Abstract

Abstract Approximately 7% of women with breast cancer have less than 40 years at diagnosis. Despite of more aggressive characteristics of these tumors, earlier diagnosis and better treatments had increased the number of cancer survivors, and topics such as hormonal treatments, previously unimportant, have now to be discussed. As the concentration of the progestin in breast tissue of patients using Levonorgestrel intrauterine system is very low, there may be a safe alternative for this population. Here we show that low-dose Levonorgestrel did not increase proliferation of breast cells suggesting that, in well-defined situations, some exogenous hormones might be used in breast cancer survivors, thus improving their quality of life. We found in controlled in vitro assays that two mammary cell lines, MCF10A and MCF7, did not show cellular proliferation when exposed to the concentration of 0.01μM Levonorgestrel, even with positive controls of proliferation carried out with Estradiol showing significant difference in both strains. Our results demonstrate that this progestin alone does not seems to be the cause of breast cancer, and our assay may be a “restarting” point for more sophisticated in vitro models that can really explain what is safe, and what is not, for breast cancer survivors.