New research from the US suggests that most American men diagnosed with prostate cancer receive aggressive treatment, even if their prostate-specific antigen (PSA) level is below the current recommended 4.0 nanograms per milliliter threshold for biopsy and their diagnosis indicates low-risk disease; the researchers argue against lowering the threshold, suggesting there is no evidence that waiting for PSA to reach the current threshold before doing a biopsy leads to significant increases in non-curable cases, whereas lowering it is likely to lead to overdiagnosis and overtreatment.
Dr Yu-Hsuan Shao, of the Cancer Institute of New Jersey, New Brunswick, and colleagues report their findings in a paper that was published online on 26 July in the Archives of Internal Medicine, a JAMA/Archives journal.
We must not forget that the big picture on prostate cancer is good news: the five-year survival rate in the US from all stages of the disease has shot up from 69 per cent in 1975 to 99 per cent in 2003, and nowadays more than 90 per cent of cases are diagnosed before the cancer has spread to other parts of the body, wrote the authors in their background information.
We can thank earlier detection and treatment for this success, but now there are concerns that perhaps localized prostate cancer is being overdiagnosed and overtreated.
Despite these concerns, some experts are pushing to bring the PSA threshold for biopsy below the currrent 4.0 nanograms per milliliter (4.0 ng/mL) threshold, based on the argument that “PSA level is associated with a continuum of cancer risk”, wrote the researchers (ie there is no cut off point).
But this push appears to lack any evidence on the risk profiles and treatment patterns in men diagnosed with prostate cancer and PSA levels of 4.0 ng/mL and under, so the authors decided to look for some.
From the Surveillance, Epidemiology and End Results (SEER) system, they found records of 123,934 American men with newly diagnosed prostate cancer from 2004 to 2006.
The researchers noted that 14 per cent of these newly diagnosed prostate cancer patients had PSA levels of 4.0 ng/mL and under, they were less likely to have a diagnosis of high-grade cancer, and more than half of them were diagnosed with low-risk cancer.
Yet when they analysed the results, the researchers found that despite the fact they had a lower risk of clinically significant disease, the treatment rates for patients with PSA levels of 4.0 ng/mL and under were similar to those whose PSA levels were between 4.0 and 20.0 ng/mL.
They also found that:
- More than 70 per cent of patients with PSA levels below 20.0 ng/mL had radical prostatectomy (complete removal of the prostate gland) or radiation therapy.
- Of patients with PSA levels at or below 4.0 ng/mL, 44 per cent had radical prostatectomy, as did 38 per cent of those with PSA levels between 4.1 and 10.0 ng/mL, and 24 per cent of those whose PSA fell between 10.1 and 20 ng/mL.
- 33 per cent of patients with PSA levels at or below 4.0 ng/mL received radiation therapy, as did 40 per cent of those with PSA values between 4.1 and 10.0 ng/mL, and 41.3 per cent of those with PSA values between 10.1 and 20 ng/mL.
The researchers estimated that if the PSA threshold for biopsy was brought down to 2.5 ng/mL, this would double to 6 million the number of men diagnosed with abnormal PSA in the US, and 32 per cent of them (1.9 million) would be diagnosed as having prostate cancer from their needle biopsy.
From these 1.9 million men, they reckoned that while 82.5 per cent would undergo treatment, only 2.4 per cent would have high-grade cancer, despite there being no evidence that delaying biopsy until the PSA level reaches 4.0 ng/mL would lead to an excessive number of potentially non-curable prostate cancers.
The researchers concluded that most men diagnosed with prostate cancer with a PSA value below the 4.0 ng/mL mark had low-risk disease but underwent aggressive local therapy and that:
“These results underscore the fact that PSA level, the current biomarker, is not a sufficient basis for treatment decisions.”
“Without the ability to distinguish indolent from aggressive cancers, lowering the biopsy threshold might increase the risk of overdiagnosis and overtreatment,” they warned.
The study was funded by the National Cancer Institute, Cancer Institute of New Jersey and Robert Wood Johnson Foundation.
“Risk Profiles and Treatment Patterns Among Men Diagnosed as Having Prostate Cancer and a Prostate-Specific Antigen Level Below 4.0 ng/mL”
Yu-Hsuan Shao; Peter C. Albertsen; Calpurnyia B. Roberts; Yong Lin; Amit R. Mehta; Mark N. Stein; Robert S. DiPaola; Grace L. Lu-Yao
DOI:10.1001/archinternmed.2010.221
Additional source: JAMA Archives.
Written by: Catharine Paddock, PhD