The acute effects of chemotherapy and radiotherapy on peripheral blood epigenetic age in early stage breast cancer patients

Genome wide DNA methylation profiling of human blood samples. The Illumina Infinium EPIC DNA methylation Beadchip was used to obtain DNA methylation profiles Survival has increased in early stage breast cancer (BC), and the late effects of cancer treatment can persist for decades. The molecular mechanisms underlying acceleration of age-related diseases after chemotherapy and radiotherapy are poorly understood. We examined epigenetic changes in peripheral blood in early stage BC patients undergoing either adjuvant radiotherapy, or adjuvant chemotherapy and radiotherapy. DNA methylation experiments were performed on peripheral blood samples from women collected prior to and following completion of adjuvant therapy. Methylation profiles were used to estimate three measures of epigenetic age acceleration - intrinsic, extrinsic, and phenotypic - as well as estimated cell counts. N=144 methylation arrays from women with breast cancer. Blood was drawn before treatment (time point 0, baseline) and after treatment. Some women were treated with radiation therapy.