A new, noninvasive blood test can reliably detect prostate cancer in patients with inconclusive PSA tests, the test’s developer, CellMax Life, recently announced.
Researchers say the company’s circulating tumor cell (CTC) blood test could reduce the number of unnecessary biopsies by up to 90 percent.
A study highlighting the test’s positive results, titled, “Prospective clinical study of a prostate cancer (PCa) rule-out blood test for PSA gray zone patients using a sensitive circulating tumor cell assay,” was presented by lead author Jacob See-Tong Pang at the 2018 ASCO Genitourinary Cancers Symposium in San Francisco, California, on Feb. 8.
A significant number of men who undergo PSA screening receive an indeterminate, or “gray zone,” result. Three out of four of these patients have a negative biopsy. Unnecessary prostate biopsies present a significant risk for side effects, including fever, infection, and bleeding. Some of these patients may require hospitalization.
Tests currently used to determine the need for biopsy, based on elevated PSA levels, have insufficient specificity and sensitivity, which leads to unnecessary biopsies in a large number of men.
“Our results suggest that this novel blood test, based on [CTCs], may offer a solution for this clinical unmet need,” See-Tong Pang said in a press release.
The company used its CMx platform to develop a blood test focused on circulating tumor cells. CTCs are cancer cells from a primary tumor that escaped into the bloodstream and are a critical factor in metastasis.
The presence of CTCs may help identify patients who would benefit from additional treatments. Research shows that CTC levels correlate with disease outcome in prostate, breast, and colon cancers. However, available methods to quantify CTCs are only useful for late-stage disease.
But the new test quantifies CTCs by using antibodies to specific proteins. Results showed that the CTC score reliably detected prostate cancer, even in patients with “gray zone” levels of PSA.
A total of 200 adults were included in the study. All patients underwent routine testing with PSA screening and a digital rectal exam. Patients with a prostate cancer diagnosis and those with PSA levels in the “gray zone” underwent a biopsy with the CellMax CTC test, which requires only 2 milliliters (about half a teaspoon) of blood.
The test demonstrated a sensitivity of 80 percent and a specificity of over 90 percent. Importantly, the researchers estimate that the new test may lead to a reduction in unnecessary prostate biopsies by up to 90 percent.
“These results are also significant because they are among the first to show that CTCs can be used for early detection of prostate cancer,” See-Tong Pang said. As a result, the company is expanding the test to 250 additional patients and to locations in the U.S.
“These results show that the CellMaxCTC test could enhance the utility of PSA testing,” said Mahul Amin, one of the study’s co-authors. Amin added that unlike current tests, which can cost between $400 and $1,000 and may not be covered by medical insurance, CellMax aims to market its test for $150.
In addition, as the biological mechanism driving the appearance of CTCs is common to all solid tumors, Cell Max expects the new blood test to be used in other cancer types, such as breast and lung cancers. CellMax CTC is currently marketed in Asia.