A Study of Serum Folate Levels in Patients Treated With Olaparib

This is a study investigating folate deficiency (lack of folic acid in the blood) in patients who take the drug olaparib to treat their advanced ovarian or breast cancer. The primary goal of this study is to determine the frequency and timing of folate deficiency, and to learn more about whether giving folic acid supplementation (vitamin) will help delay or avoid deficiency in these patients. Deficiency can cause doctors to reduce or stop treatment with olaparib. In this case, patients are not getting the best treatment for their cancer due to the unwanted side effect.