Hormone therapy to reduce levels of estrogen in breast cancer patients, which has long been used for the purposes of tumor reduction prior to surgical extraction, may cause some tumors to mutate and grow, according to a new study published Nature Communications.
For the study, researchers examined 22 breast tumors prior to and post four months of hormone inhibiting therapy. Eighteen of the tumors analyzed were genetically complex and responded dynamically to the hormone deprivation therapy. In one instance, 92 percent of mutations detected in the initial tumor were absent from samples taken four months after the initiation of hormone therapy. The mutations suggest tumors are capable of spawning new sub-clones that can subsequently facilitate tumor survival and growth despite therapy.
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"Estrogen-receptor-positive breast cancers are not created equal," said co-senior author Elaine R. Mardis, PhD, the co-director of the McDonnell Genome Institute at Washington University School of Medicine in St. Louis. "Each woman's disease can have a range of responses to estrogen-lowering drugs. This study demonstrates that reducing estrogen levels in estrogen-receptor-positive breast cancer changes the genetics of the tumor, and these changes may be important for deciding how best to treat a patient after the surgical removal of the tumor."
The findings also suggest tumor reanalysis after hormone therapy and prior to surgery may be highly beneficial in the treatment of breast cancer.
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