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Prostate specific antigen testing and digital rectal examination before and during a randomized trial of screening
P M Beemsterboer1, H J de Koning, R Kranse
1Departments of Public Health and Urology, Erasmus University Rotterdam, Health Council of The Netherlands.
Purpose:
Worldwide 2 large-scale randomized screening trials for prostate cancer have been initiated. Determining prostate specific antigen (PSA) involves a simple test that may influence the outcome of these trials if frequently done in the control arm or before study enrollment. We quantified PSA and digital rectal examination before and during the screening trial in Rotterdam, The Netherlands and in the general population.
Materials And Methods:
Trial participants were administered study intake questionnaires on tests done before study participation. Data on PSA from the regional general practice laboratory were correlated with participant data. Various sources were used to quantify PSA tests and digital rectal examinations in the general population.
Results:
Of men 55 to 74 years old 45% underwent digital rectal examination at 1 time and 13% reported that PSA was tested before trial participation. Each rate increased with age. No statistically significant effect of former PSA testing or digital rectal examination on the cancer detection rate was identified. The rate of PSA determination after initial screening and/or randomization in the control arm was 2-fold that in the screening arm (76 versus 33/1,000 person-years). PSA determination initially decreased in the screening arm but increased rapidly after some time. The number of PSA determinations in the general population was estimated to be 45/1,000 person-years at ages 55 to 69 years.
Conclusions:
PSA testing was moderate in the control arm but if different men undergo this test each year, the contamination rate may become rather high. In the final analysis of mortality PSA testing should be considered.