A simple blood test that detects tumor cells circulating in the blood shows promise as a new way to predict high or low risk of a breast cancer relapse. This is according to data presented today at the 40th annual San Antonio Breast Cancer Symposium. A proof-of-concept study by the ECOG-ACRIN Cancer Research Group (ECOG-ACRIN) measured the prevalence of circulating tumor cells (CTCs) in blood samples from patients cancer-free five years or more after diagnosis, then associated CTC presence with a later recurrence.
"Late recurrence five or more years after surgery accounts for at least one-half of recurrences of breast cancer, and there are no tests that identify who is at highest risk. We found that in women who were cancer-free five years after diagnosis, about 5 percent had a positive CTC test," said lead researcher Joseph A. Sparano, MD, vice chair of the ECOG-ACRIN Cancer Research Group, Philadelphia, and associate director for clinical research at Montefiore Medical Center, Albert Einstein Cancer Center, New York.
"More importantly ...", Dr. Sparano continued, "...we also found that a positive test was associated with a 35 percent recurrence risk after two years, compared with only 2 percent for those with a negative CTC test."
The concept is to explore the use of the CTC blood test in a new way. Currently, the test is FDA-approved for use by physicians to monitor response to treatment in patients with advanced breast, colon or prostate cancer, but not early stage cancer. A rise in the number of circulating tumor cells in the blood in patients with advanced disease may indicate trouble before it shows up on a scan. In this study, the research team evaluated this test in a different setting--individuals alive and cancer-free about five years after their diagnosis and potentially cured, but still at risk for having a recurrence of their disease.
"Our ultimate goal is to use blood tests like this to tailor treatment in a way that minimizes recurrence risk for those at high risk, and spare treatment for those at low risk who may be unlikely to benefit from it," Dr. Sparano said. "The findings of this analysis provide strong evidence to further evaluate this new risk assessment approach using CTC and other blood-based tests in this setting".
The test was done on a single blood sample provided by 547 breast cancer patients who had been diagnosed more than five years prior and treated as part of a large ECOG-ACRIN breast cancer treatment trial, E5103. This group of patients had stage two or three breast cancer, and the cells in their tumors were HER2-negative.
Many women in E5103 remain cancer free and are being followed for their breast cancer status as part of standard care. Dr. Sparano and colleagues set up a biobank and invited these patients to contribute additional specimens for future research into the reasons for late recurrence. The biobank was established by ECOG-ACRIN and the Coalition of Cancer Cooperative Groups with funding from the Breast Cancer Research Foundation, National Cancer Institute, and Susan G. Komen.