Usefulness of PSA test to identify prostate cancer may be diminishing
MedWire News: US study results show that the usefulness of the prostate-specific antigen (PSA) test as a screening tool for prostate cancer may be diminishing over time.
Using patient data gathered between 1990 and 2006 at the Cleveland Clinic in Ohio, Jeanette Potts (University Hospitals, Cleveland) and colleagues report that PSA sensitivity and specificity decreased consistently over time, such that in recent years it showed “a predictive value comparable to a coin toss.”
The research was prompted by the disparity in prostate cancer incidence and mortality between Black and White men in the USA, which could be caused by modifiable factors such as screening practices, the team explains in the journal Cancer.
The average age at first biopsy was not significantly different between the 911 Black and 4659 White men whose data was included in the study, at 65.9 years and 65.6 years, respectively.
However, despite a change in standard community practice to begin screening Black men earlier than White men, at age 40 years, and the lowering of PSA thresholds for biopsy from 4.0 to 2.5 ng/ml, in 2000 the researchers found no significant decrease in the average age at first prostate biopsy following an abnormal PSA test result.
The average age at initial biopsy was approximately 68 years among White men and 67 years among Black men in 1990–1991, dropping only slightly to approximately 66 years and 65 years among White and Black men, respectively, in 2006.
“This observation was unexpected,” writes the team.
Higher median PSA levels prior to first biopsy were observed in Black men than in White men overall during the study period, at 8.0 versus 6.7 ng/ml. However, PSA measurements decreased by an average of 4.6% and 2.3% per year in each race, respectively, and differences between the races diminished over time.
The association between PSA levels and cancer detection also became nonsignificant as PSA levels lowered over the years. The area under the receiver-operator characteristics curve was close to 0.5 during most years after 2000, indicating that “PSA elevation was as effective as a coin toss in predicting subsequent cancer detection on biopsy,” say Potts et al.
Overall, cancer was detected by biopsy more frequently in Black than in White men, with an odds ratio of 1.34. However, this difference became nonsignificant after adjustment for PSA level.
The researchers believe their results highlight that significant differences exist between expectations based on published recommendations and the realities of clinical practice.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010
By Sarah Guy