PET Measures Breast Cancer Patients Response to Therapy

Noninvasive imaging can measure how well patients with the most common form of breast cancer, estrogen receptor-positive type, respond to standard aromatase inhibitor therapy after only two weeks and demonstrates similar findings that more invasive needle sampling identifies, according to new findings.

Utilizing positron emission tomography (PET) scanning and a glucose analogue called fluorodeoxyglucose (FDG), a research team led by Hannah Linden, M.D. and David Mankoff, M.D., from the Seattle Cancer Care Alliance and the University of Washington (Seattle, USA), scanned 21 patients before and after two weeks of aromatase inhibitor therapy. Many of the patients also underwent a needle biopsy as a control measure to compare the two techniques.

The results--16 of the 21 patients had a greater than 20% decline in FDG values-- "paralleled perfectly” with earlier research performed by UK-based researchers who used needle biopsies to measure whether the proliferation of cancer cells was slowed by therapy, according to Dr. Linden, who is a breast cancer oncologist.

"Our findings are exciting because they suggest that we can measure a patient's response to therapy noninvasively, and PET scanning provides us simultaneous quantitative metabolic measurements at multiple tumor sites,” Dr. Linden said. "PET has the potential to be a powerful tool to help doctors make important treatment decisions in as little as two weeks instead of two or more months.”

Patients with estrogen receptor-positive cancer have remained largely unevaluated in clinical trials because they are very difficult to image, according to Dr. Linden. "Our work allowed us to study a common problem in a way that's not been done before and to help more people. More work needs to be done but in my mind this was a homerun,” Dr. Linden said.

The study's findings were presented at the American Society of Clinical Oncology (ASCO) annual meeting, held May 29-June 2, 2009, Orlando, FL, USA.

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