"Although further studies are needed before the PET scan biomarker can be reliably used on a wide scale, the results of this study have the potential to advance the options for precision medicine in women with breast cancer," says Vered Stearns, M.D., professor of oncology, co-director of the Breast and Ovarian Cancer Program at Johns Hopkins and senior author of the manuscript published in the February 2019 issue of Journal of Clinical Oncology. "This study, coupled with other complete and ongoing investigations at the Breast and Ovarian Cancer Program at Johns Hopkins, is at the forefront of providing true precision medicine to patients with breast cancer."
For the study, investigators fully evaluated 83 of 88 women with stage II or stage III estrogen receptor (ER)-negative, HER2-positive breast cancer recruited from nine Translational Breast Cancer Research Consortium (TBCRC) medical facilities across the United States, including The Johns Hopkins Hospital.
PET scans that use radioactive tracers to detect sugar uptake in cancer cells were conducted prior to and 15 days after patients were given the first of four cycles of pertuzumab and trastuzumab (without chemotherapy) over a 12-week period. Those two drugs are monoclonal antibodies that precisely target particular proteins on HER2-positive cancer cells and are widely used to treat HER2-positive breast cancers, usually in combination with chemotherapy drugs that poison such cells and carry more toxic side effects.
The researchers sought to evaluate whether early changes on a PET scan - images taken during the first stages of targeted therapy - can help determine whose tumor will disappear completely following HER2-targeted treatment.
After two weeks of treatment, researchers found they could predict whether a patient would respond to HER2-targeted treatment without chemotherapy. In approximately 56 percent of cases (44 patients), a predictive biomarker was identified that could have the potential to be a useful early response assessment tool.
Lead author Roisin Connolly, M.B.B.Ch., M.D., associate professor of oncology at the Kimmel Cancer Center, said the change in sugar uptake on PET scans from baseline to two weeks after starting treatment, and the value at the two-week time point itself, had the best ability to predict response to HER2-directed therapy with high sensitivity and very high negative predictive value. High sugar levels two weeks after treatment, says Connolly, indicate the tumor likely will not fully respond to antibodies alone and will need chemotherapy.
MEDICA-tradefair.com; Source: Johns Hopkins Medicine
