Prostate Cancer Test Results Vary Based on Liquid Biopsy Panel

A small number of liquid biopsy test results from different providers matched for overlapping genetic sequences.

Patients who are being tested for prostate cancer may receive drastically different results depending on the provider of commercial liquid biopsies , according to a study published by JAMA Oncology.

Liquid biopsy is a non-invasive technique used to detect and sequence circulating tumor DNA as an alternative to tumor tissue sequencing. Physicians use the test results to personalize treatment for patients depending on their profiles.

The authors said the study results suggest that what patients with prostate cancer are prescribed could be affected by the commercial provider that is used for the biopsy, according to the study.

The researchers compared the results of the Guardant360, which sequenced at least part of the coding sequences for 73 genes, and the PlasmaSELECT, which sequenced the coding segments for 64 genes.

Both laboratories were licensed by Clinical Laboratory Improvements and accredited by the College of American Pathologists, in addition to reporting high sensitivity and high specificity, according to the authors.

The study authors found that the panels differed in which genes were assessed. Of the 40 patients included in the study, 25 had 1 or more mutations that were reported by both tests, according to the study.

Significantly, even when the panels were analyzing DNA from the same blood sample, the results varied. When results within the overlapping genetic sequences were compared, the companies’ results matched in only 7.5% of cases, according to the study.

The authors found that the companies’ results matched for at least 1 of the mutations in 15% of patients.

However, no mutations covered by the tests were detected in 40% of patients, highlighting significant gaps in efficacy, according to the authors.

The goal of the study was to determine the best lab test for patients being seen at a cancer clinic.

“We wanted to make the best choice for our patients, so we started submitting the samples to both places at the same time to compare results,” said researcher Gonzalo Torga, MD.

Patients with prostate cancer respond differently to treatments based on the type of mutations their tumors have. To address this challenges, oncologists use liquid biopsies to guide their treatment approach and monitor patient response.

Because liquid biopsies are costly, patients typically only have 1 sent out. These findings suggest that the results of the tests may not be entirely accurate, which could have an impact on treatment, according to the study.

“Liquid biopsy is a promising technology, with an exceptional potential to impact our ability to treat patients, but it is a new technology that may need more time and experience to improve,” Dr Torga said. “We can’t tell from these studies which laboratory’s panel is better, but we can say that certification for these laboratories must improve.”