This year’s San Antonio Breast Cancer Symposium (SABCS), being held December 5-9, 2017 discussed data from many promising and exciting studies. One topic of discussion through the week has been the treatment of Hormone Receptor Positive (HR+) breast cancer, and how to deal with recurrence. HR+ breast cancers account for over half of breast cancer cases, and the disease is characterized by a high rate of recurrence compared to breast cancers that are Hormone Receptor Negative (HR-).
A study presented on Friday, December 8th, focused with the possibility of predicting late recurrence by monitoring Circulating Tumor Cells (CTC) in HR+ breast cancer patients.
We found that results from a single positive Circulating Tumor Cells assay five years after diagnosis, provides independent prognostic information for late recurrence…
Circulating Tumor Cells (CTC)
Results from this study, which was coordinated by the ECOG-ACRIN Research Group and was funded by the Breast Cancer Research Foundation, Susan G. Komen Foundation, and the National Cancer Institute, showed that in patients with hormone receptor (HR+) HER2-negative stage II and III breast cancer, who had no evidence of recurrence, were at an increased risk for late recurrence if they had CTCs found in their blood five years after diagnosis.
Circulating Tumor Cells (CTC), are tumor cells that have detached from the primary tumor, and now make their way around the body through the blood stream of lymphatic system. These cells are then able to travel and potentially create a new source of tumor growth in other organs. This cancer metastasis is responsible for most cancer-related deaths, and unfortunately, CTCs are not easily detected. 
Predicting Risk of Recurrence
The study enrolled 546 patients, 4.8% of which had tested positive for CTC.
Among with HR+ breast cancer, 5.1% tested positive for CTC. After a median follow up of 1.6 years, data showed that HR+ breast cancer patients who had a positive CTC result were nearly 20 times more likely to have recurrence.
Data showed a 35% positive predictive value for these patients who tested CTC positive, and the negative predictive value was 98%. In patients in this study who had hormone receptor negative (HR-) breast cancer, 4.3% tested CTC positive. However, a positive CTC assay was not associated with recurrence for this group.
Researchers in this study obtained this data by measuring CTCs in blood samples using the CELLSEARCH CTC assay. The samples were taken between 4.5 and 7.5 years after initial diagnosis, and no patients had evidence of recurrence at the time. 
“We found that results from a single positive CTC assay five years after diagnosis, provides independent prognostic information for late recurrence,” stated Joseph A. Sparano, MD, associate director for clinical research, Montefiore Einstein Center for Cancer Care, Albert Einstein Cancer Center, New York.
“This provides proof of concept that liquid biopsy-based biomarkers may be used to stratify risk for late recurrence and possibly inform treatment or clinical trial options,” Sparano said.
Clinical Validity of CTC Assays
According to Sparano, the results from the study were surprising. While it was expected that patients with CTCs would have a higher rate of recurrence, researchers did not expecting to see this risk to become so high after a short period of time.
“This study provides strong evidence of the clinical validity of the CTC assay as a prognostic biomarker for late recurrence in HR-positive breast cancer, which accounts for about one-half of all recurrences,” stated Sparano,
“Utilizing the CTC assay for prognostic analysis may aid in a more accurate identification of patients who would most benefit from extended adjuvant endocrine therapy or other treatment options,” he added.
And while this study provides evidence that CTC assays could help identify patients who would benefit from therapies to reduce recurrence risk, they may also help address when further treatments may, on the other hand, not be necessary in the long run. In fact, researchers may now plan to study how a single or multiple negative CTC tests would serve to predict when extended adjuvant endocrine therapy beyond five years may be spared, as it could be unnecessary for certain patients.
Last Editorial Review: December 8, 2017
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