The worst news for cancer survivors is finding out their disease has returned. Unfortunately, this threat is ever looming, but scientists are exploring ways of accurately determining the risk of recurrence. By analyzing samples from 62 patients, researchers from the University of Edinburgh have identified genetic changes that may indicate the likelihood of breast cancer relapse in women taking a common form of hormone therapy.
Years or even decades after surgery and apparently successful adjuvant therapy, the possibility of the disease manifesting again persists. While aromatase inhibitors have been shown to increase outcomes, by up to 40%, this type of treatment is only effective for patients who have estrogen receptor (ER) alpha-positive tumors. Estrogen is still produced in the body after menopause and can stimulate tumor growth, which is why Letrozole or other hormone therapy drugs are prescribed.
Investigators noticed that hormone therapy almost immediately initiated alterations in the genes that were switched on in the tumors. After treatment with Letrozole, samples that had at least a 40% initial reduction in tumor size were placed in either of two groups, “dormant” or “acquired resistant”.
“Treatment resistance is hard to study and laboratory experiments often do not closely resemble the situation in patients. This is the first time we have been able to investigate genetic changes in individual patients’ tumours over time”, noted Dr. Andy Sims, Senior Research Fellow at MRC Institute of Genetics and Molecular Medicine.
The cancer cells displayed epigenetic changes, chemical signatures that were absent in samples that developed resistance to hormone therapy but were present in tumors that had started growing again after shrinking initially.
“This is a promising early finding that could help us better understand how some breast cancers become resistant to therapy and what we can do about it. Drug resistance is a major hurdle that we must overcome if we are to finally stop women dying from breast cancer”, added Dr. Simon Vincent, Director of Research, Breast Cancer Now.
The changes in epigenetics pathways including DNA methylation and histone acetylation could become a target for new treatments. Reducing treatment resistance and lowering the risk of relapse would significantly improve the lives of cancer patients.
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