How the results were obtained
419 breast cancer patients were enrolled in the study, and each patient had their blood serum taken twice over the course of the progression of their cancer. The first sample was taken before the patient underwent their first round of chemotherapy, and the second round was taken after chemotherapy as completed. The results of the blood serum analyses showed that abnormal DNA methylation in the blood serum prior to chemotherapy was a clear marker of poor prognosis. Most significantly, cancer cells did not need to be present in the bloodstream for the DNA methylation test to give these results.