The failure of prostate cancer screening


The early detection of various types of cancer has been one of the key factors in significantly increasing the chances of recovery, along with substantial improvements in various treatments. In fact, the five-year survival rate for cancer patients in Spain has doubled in the last forty years (it is currently 55% for men and 61% for women). Among all types of cancer, breast and prostate cancer stand out for their excellent prognosis in the vast majority of cases: more than 90% of patients survive for five years.

There are currently three national cancer screening programmes in Spain: mammography for women aged 50–69 to detect possible breast cancer; faecal occult blood testing for people aged 50–69 to detect possible colorectal cancer; and cervicovaginal cytology and human papillomavirus screening for women aged 25–65 to detect possible cervical cancer.

For decades, doctors in many countries used a screening method for prostate cancer that was eventually discouraged worldwide after a long scientific controversy: the prostate-specific antigen (PSA) test. PSA was first identified in 1970 through the research of pathologist Richard Ablin and his team. This protein, secreted by the prostate gland, is found in high concentrations in semen. However, it was soon discovered that PSA was also elevated in the blood of men with prostate cancer.

The knowledge that it was possible to detect potential prostate cancer with an inexpensive and simple (blood) test soon led to PSA testing in men as an opportunistic screening method (where the test is performed when the patient comes to the doctor’s office for other reasons). At the time, however, there were few scientific studies that rigorously assessed the risk/benefit of this practice for improving the prognosis of prostate cancer. Its benefit was simply assumed.

Over the decades, however, the emergence of large clinical trials (comparing outcomes between groups of men who were screened for PSA and those who were not) confirmed the bad news: men who were screened with a PSA test experienced no health benefit. At best, there was little or no reduction in prostate cancer mortality. They were also exposed to more harm from unnecessary treatment. Since 2012, various health bodies (such as the US Preventive Services Task Force) and medical associations have come out against the test.

It may seem counterintuitive. If we detect cancer earlier, when the cancer cells are still limited in their ability to spread, we have a better chance of cure if we treat it earlier. So why has PSA not worked for this purpose?

The main reason is the nature of prostate cancer: in many cases, the tumour that starts in the prostate grows so slowly that even if it is allowed to grow, it does not pose a threat to a man’s health. What happens when we do a PSA test in these cases? Well, we might diagnose and treat as cancer something that would never have caused any harm if we had not seen it. Predicting cancer is important, but sometimes it is not the best strategy.

© Mètode 2023 - 119. #Storytelling - Volume 4 (2023)
PhD in Regenerative Medicine and disseminator (Madrid, Spain). Author of Si escuece, cura (Cálamo, 2019).