The pinprick that improves cancer diagnosis: rapid blood test brings prostate cancer hope

A new blood test, used in combination with the current prostate specific antigen (PSA) test, could help men avoid unnecessary and invasive biopsies, over-diagnosis and over-treatment.

Prostate cancer is the most common cancer in Western men, with 1.3 million new cases being diagnosed each year worldwide. It’s currently detected using a blood test that measures PSA levels.

Although it provides early diagnosis, the PSA blood test has a high false positive rate, with about 75 per cent of all PSA positive results ending up with negative biopsies that don’t find cancer.

Existing risks and treatment concerns

When high PSA levels are detected in the patient’s blood, they then have to undergo an invasive tissue biopsy of the prostate gland. This procedure carries a significant risk of bleeding and infection. Moreover, the majority of these patient biopsies do not find any cancer present in the tissue.

However, most diagnosed early-stage prostate cancers are not fatal if left untreated. This means that the current practice of the combined PSA test and biopsy for prostate cancer patients results in unnecessary biopsies and over-diagnosis and overtreatment of many men.

Accuracy and speed of diagnosis

The new prostate cancer test (the Parsortix® system from ANGLE plc) detects early cancer cells, or circulating tumor cells (CTCs), that have left the original tumour and entered the bloodstream before spreading around the body.

By measuring intact living cancer cells in the patient’s blood, rather than the PSA protein that may be present in the blood for reasons other than cancer, the test potentially offers a more accurate result.

The study, published in the Journal of Urology in 2020, looked at the use of the CTC test in 98 pre-biopsy patients and 155 newly diagnosed prostate cancer patients enrolled at St Bartholomew’s Hospital in London.

Professor Lu’s research team found that the presence of CTCs in pre-biopsy blood samples were indicative of the presence of aggressive prostate cancer, and efficiently and non-invasively predicted the later outcome of biopsy results.

Discovering the presence of aggressive prostate cancer

When the CTC tests were used in combination with the current PSA test, it was able to predict the presence of aggressive prostate cancer in subsequent biopsies with over 90 per cent accuracy, better than any previously reported biomarkers.

Moreover, the number and type of CTCs present in the blood was also indicative of the aggressiveness of the cancer. Focusing on more aggressive prostate cancer may reduce over-treatment and unnecessary biopsies for benign and non-aggressive conditions.

‘A paradigm shift in the way we diagnose prostate cancer’

Commenting on the research, Professor Yong-Jie Lu from Queen Mary’s Barts Cancer Institute notes: “The current prostate cancer test often leads to unnecessary invasive biopsies and over-diagnosis and overtreatment of many men, causing significant harm to patients and a waste of valuable healthcare resources. There is clearly a need for better selection of patients to undergo the biopsy procedure.

“Testing for circulating tumour cells is efficient, non-invasive and potentially accurate, and we’ve now demonstrated its potential to improve the current standard of care. By combining the new CTC analysis with the current PSA test, we were able to detect prostate cancer with the highest level of accuracy ever seen in any biomarker test, which could spare many patients unnecessary biopsies. This could lead to a paradigm shift in the way we diagnose prostate cancer.”

As this is a single centre study, the results need to be further validated in other independent research centres before the CTC test is available either privately or on the NHS in the UK, which could take a further 3–5 years. Clearance by the US Food and Drug Administration could also take 3–5 years.

This work was funded by Orchid Cancer Appeal, Cancer Research UK and ANGLE plc (which manufactures the Parsortix system). The funding sources had no role in the design of the study; the collection, analysis, or interpretation of the data; or the writing of the research paper.