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Scintigraphy Predicts Success of Hormone Therapy for Breast Cancer Patients
A new protocol that involves imaging at the molecular level could help physicians predict which breast cancer patients will respond best to hormone therapy, according to a new study.
Because the hormone estrogen promotes the growth of breast cancer in many women, physicians may try to treat the cancer by blocking estrogen’s effects or lowering levels of the hormone. However, with conventional imaging techniques like computed tomography and magnetic resonance, it can take several months to determine if hormone therapy is working.
Researchers studied somatostatin receptor scintigraphy as a predictor of which patients would respond to hormone therapy. Somatostatin is a hormone that inhibits the secretion of growth hormone. Approximately 15 percent of breast cancers have somatostatin receptors on their surface. Effective estrogen therapy in patients may result in reduced somatostatin uptake at the cell surface in breast tumors, which could be seen on scintigraphy.
In the study, the researchers looked at 20 patients with a diagnosis of advanced breast cancer who were scheduled for hormone therapy. The patients underwent technetium-99m, or 99mTc, depreotide scintigraphy before and three weeks after initiating hormone therapy. Depreotide is an analog of somatostatin. The researchers obtained follow-up data by means of physical examination, imaging and blood analysis.
At six months after initiation of treatment, eight patients had stable disease and appeared to be responding to hormone therapy, while 10 patients had progressive disease, which put them in the nonresponder category.
Baseline scintigraphy had a positive predictive value of 73 percent and a negative predictive value of 100 percent. Radiopharmaceutical uptake decreased in responders to treatment and increased in nonresponders.
“As such, baseline 99mTc-depreotide scintigraphy combined with the changes in tracer uptake between the baseline and follow-up scan predicted endocrine responsiveness with an accuracy of 100 percent,” said Bieke Van Den Bossche, M.D., Ph.D., of Ghent University Hospital in Ghent, Belgium. “Sequential 99mTc-depreotide scintigraphy could allow for separation of responders and nonresponders immediately or as early as three weeks after initiation of treatment.” The study appeared in the January edition of the Journal of Nuclear Medicine.
Dr. Van Den Bossche suggested a protocol that would begin with a baseline scintigraphy scan. Patients with negative scans would be considered nonresponders to hormone therapy, while patients with positive scans would undergo a repeat scan three weeks after the baseline scan. If the radiotracer uptake had decreased, they would be considered responders to hormone therapy, while those who experienced an increase in radiotracer would be considered nonresponders, and physicians would consider alternative treatments.
The researchers plan to confirm their findings on a larger group of patients.