Blood Test Can Identify Patient Response to Prostate Cancer Treatments

A blood test can help detect whether patients with advanced prostate cancer will respond to a certain treatment, according to a new study. This approach could help better inform the choice of therapy and lead to improved outcomes.

In the study, researchers used a liquid biopsy test developed by Epic Sciences to examine circulating tumor cells (CTCs) in blood samples from 142 patients with advanced prostate cancer deciding whether to switch from hormone-targeting therapy to chemotherapy.

Most patients undergo therapy with androgen-receptor signaling (ARS) inhibitors as the first-line treatment for the disease. These drugs target the hormones that fuel prostate cancer cell growth, making them an effective first-line therapy, the researchers wrote. However, cancer cells can become resistant to ARS inhibitors through the production of a protein called AR-V7, leading patients to second-line therapy options, such as chemotherapy.

According to the researchers, the test identifies whether or not a patient’s CTCs contain AR-V7 in the cell’s nucleus. They found that patients who tested positively for this protein responded best to taxane-based chemotherapy, while those who tested negative responded best to hormone-targeting therapy with ARS inhibitors.

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The researchers noted that the approach enables a higher sensitivity of CTC detection than the only assay cleared by the FDA, as well as a protein biomarker assessment on individual CTCs.

The study aimed to predict the best treatment for patients who had already undergone at least 1 round of hormone-target therapy. However, future studies could work to assess the use of CTC blood tests in determining the optimal therapy earlier at earlier care decisions for advanced prostate cancer, the researchers noted.

“The study focused on a critical decision point when patients and their oncologists are choosing what therapy to pursue next,” Allison Allan, PhD, scientist at Lawson and Chair, Department of Anatomy and Cell Biology at Western University’s Schulich School of Medicine and Dentistry, said in a press release. “We are addressing a critical unmet need by validating that a blood test or liquid biopsy can be used to select a therapy most likely to extend a patient’s life.”

The research team intends to collaborate further with Epic Sciences to study different versions of the CTC blood test for other types of cancer. The test is now commercially available in the United States as the Oncotype DX AR-V7 Nucleus Detect.

References

Scher HI, Graf RP, Schreiber NA, et al. Assessment of the validity of nuclear-localized androgen receptor splice variant 7 in circulating tumor cells as a predictive biomarker for castration-resistant prostate cancer. JAMA Oncology. 2018. doi:10.1001/jamaoncol.2018.1621

Blood test can predict optimal treatment for advanced prostate cancer, study finds [news release]. Lawson Health Research Institute’s website. 2018. https://www.lawsonresearch.ca/blood-test-can-predict-optimal-treatment-advanced-prostate-cancer-study-finds. Accessed January 25, 2018.