A new blood test that looks for circulating tumor cells could significantly improve the diagnosis of prostate cancer and avoid unnecessary biopsies and treatments.

Combining the new test with prostate specific antigen (PSA) results can yield a diagnosis of aggressive prostate cancer that is more than 90% accurate, according to a Journal of Urology study.

This level of accuracy is higher than that of any other biomarker for prostate cancer, says senior and corresponding study author Dr. Yong-Jie Lu, a professor of molecular oncology at the Barts Cancer Institute of Queen Mary University of London in the United Kingdom.

"This could lead to a paradigm shift in the way we diagnose prostate cancer," he adds.

Circulating tumor cells are cancer cells that have left the original tumor and entered the bloodstream. Once cancer cells are in the bloodstream, they can spread to other parts of the body.

PSA test not enough to diagnose cancer

PSA is a protein that the prostate produces. If there is cancer in the prostate, the gland releases more PSA into the blood. Therefore, raised levels of PSA in the blood can be a sign of prostate cancer.

However, other prostate conditions, such as inflammation or noncancerous enlargement of the gland, can also raise PSA levels.

So, to confirm the presence of cancer, the individual undergoes a biopsy, an uncomfortable procedure in which the surgeon removes pieces of the prostate and sends them for tissue analysis.

A biopsy of the prostate is not only invasive but also risky, with a high chance of bleeding and infection.

Also, the biopsy results of most men with raised PSA levels show that they do not have cancer.

Even when prostate biopsies do reveal the presence of cancer, in most cases, the tumor is not aggressive and will not be fatal if doctors leave it untreated.

Need for a test better than PSA and biopsy

The current method of diagnosing prostate cancer by combining the PSA test with a biopsy leads to many pointless biopsies, over-diagnoses, and unnecessary treatments.

Such a method can cause harm to individuals and waste precious time and resources in the healthcare system.

"There is clearly a need for better selection of patients to undergo the biopsy procedure," Prof. Lu urges.

For the study, he and his colleagues carried out the new blood test in 98 males who had not yet had a biopsy and 155 others who had just received a diagnosis of prostate cancer but not yet undergone treatment. All the participants were attending St Bartholomew's Hospital in London.

The researchers saw that the presence of circulating tumor cells in the prebiopsy blood samples was predictive of aggressive prostate cancer that subsequent biopsies detected.

In addition, from the level of circulating tumor cells, the team was able to assess the aggressiveness of the cancer.

When combined with the PSA test, the circulating tumor cell test was able to predict with 90% accuracy, which men would receive an aggressive prostate cancer diagnosis from biopsy results.

Test ready 3–5 years after validation

Further studies—using results from several independent centers—should now confirm these findings, note the researchers.

The team expects the test to be available, following regulatory approval, around 3–5 years after researchers have completed validation studies.

Around 1 in 9 men will have prostate cancer during their lifetime, according to the American Cancer Society (ACS).

The ACS estimate that more than 174,000 men will find out that they have prostate cancer and 31,620 will die of it in the United States during 2019.

Although it is a serious disease, most men who have prostate cancer do not die of it. There are more than 3.1 million men alive in the US today who have received a diagnosis of prostate cancer.

"Testing for circulating tumor cells is efficient, noninvasive, and potentially accurate, and we've now demonstrated its potential to improve the current standard of care."

—Prof. Yong-Jie Lu