Prostate Cancer Overdiagnosis
Overdiagnosis
Overdiagnosis refers to the detection by screening of conditions that would not have become clinically significant.
When screening finds cancer that would never have become clinically significant, patients are subject to the risks of screening, confirmatory diagnosis, and treatment, as well as suffering potential psychosocial harm from anxiety and labeling.
Overdiagnosis is of particular concern because most men with screening-detected prostate cancers have early-stage disease and will be offered aggressive treatment.
A number of reports have raised concerns about the risk of overdiagnosis with screening:
Overdiagnosis refers to the detection by screening of conditions that would not have become clinically significant.
When screening finds cancer that would never have become clinically significant, patients are subject to the risks of screening, confirmatory diagnosis, and treatment, as well as suffering potential psychosocial harm from anxiety and labeling.
Overdiagnosis is of particular concern because most men with screening-detected prostate cancers have early-stage disease and will be offered aggressive treatment.
A number of reports have raised concerns about the risk of overdiagnosis with screening:
- While the lifetime risk of being diagnosed with prostate cancer has increased from 1 in 11 to 1 in 6, the lifetime risk of dying from prostate cancer has remained around 1 in 34 following the advent of PSA testing [3].
- Although about 80 percent of detected cancers are considered clinically important based on tumor size and grade [149], these are relatively crude prognostic markers. Autopsy series in men who died from other causes have shown a 30 to 45 percent prevalence of prostate cancer in men in their fifties and an 80 percent prevalence in men in their seventies [150-152].
- A study that applied computer-simulation models of PSA testing to SEER cancer incidence data estimated that 29 percent of cancers detected in whites and 44 percent of cancers detected in blacks were overdiagnosed [153]. An updated analysis, that also used ERSPC Rotterdam clinical data, estimated an overdiagnosis fraction ranging from 23 to 42 percent among cancers diagnosed by PSA screening [154].
- Similarly, a study that applied simulation models to the results of the ERSPC estimated a 50 percent overdetection rate with annual screening for men ages 55 to 67 [17]. Given that the screening group in the ERSPC had a 71 percent higher cumulative incidence of prostate cancer than the control group (8.2 versus 4.8 percent) [13], the potential absolute risk for overdiagnosis is substantial.
- A study examined the number of men diagnosed and treated for prostate cancer in the United States (US) each year after 1986, the year before PSA screening was introduced, until 2005 [155]. The study estimated that approximately 1.3 million additional men were diagnosed with prostate cancer as a result of screening, of whom approximately 1 million were treated. Assuming that the entire decline in prostate cancer mortality in the US from 1986 through 2005 was due to screening, an extremely optimistic assumption for PSA screening, approximately 23 men had to be diagnosed and 18 men treated for prostate cancer to prevent one death. The authors concluded that most of the additional cases of prostate cancer found since 1986 represent overdiagnosis.