An epidemiologist's viewpoint on screening.

Prostate cancer is an important disease causing a considerable number of new cases, deaths and premature loss of life each year. Three screening tests have been suggested: DRE, TRUS and PSA measurement in venous blood. From aggregated data from studies examining the performance of these tests, DRE or PSA measurement look the most promising with respect to their estimated detection rates and false positive rates (detection rate [DR] = 68%, false positive rate [FPR] = 5% for DRE and DR = 79%, FPR = 8% for PSA with a cut off of > 4 micrograms/l). However, these results are tentative-more research is needed on the performance of these screening tests. In particular, the prevalence of prostate cancer in the studies was considerably higher than that expected in the general population and so the OAPR estimates derived are more favourable than predicted. A randomized controlled trial of prostate cancer screening is needed to know whether screening reduces mortality from this disease, although this would take about 10 years to perform. Current stage distribution and 5 year survival data suggest that if screening could increase the proportion of cancers diagnosed at the localized clinically inapparent stage from 23% (currently diagnosed) to 100%, this would represent an equivalent reduction in mortality of 48%-about 1500 lives saved per year if screening were offered to 55-74 year old men. When more substantive information is available on the potential screening tests, it may be appropriate to conduct a randomized controlled trial. In the meantime, any ad hoc screening should be strongly discouraged.

Feasibility study of a randomised trial of ovarian cancer screening among the general population.

OBJECTIVE: To determine the feasibility of a randomised trial of ovarian cancer screening among women attending a breast cancer screening centre. DESIGN: Randomised controlled trial of ovarian cancer screening using transvaginal ultrasonography as a primary screening test and colour Doppler imaging as a secondary screening test in the screened group and no intervention in the control group. SETTING: Reading breast cancer screening centre (United Kingdom). SUBJECTS: 8678 women, without a bilateral oophorectomy or hysterectomy, aged between 50 and 64 attending for NHS breast cancer screening between September 1989 and February 1993. MAIN OUTCOME MEASURES: Uptake of ovarian cancer screening among eligible women and the screening false positive rate (considered as the referral rate to a gynaecologist for surgical intervention). RESULTS: 82% (7124/8678) of eligible women agreed to join the trial and were randomly allocated in equal numbers to each arm of the trial. 3280 women had an initial scan. The false positive rate after ultrasonography alone was 2.9% (86/2952), but this dropped to 0.5% after colour Doppler as a secondary screening test. One stage I primary ovarian cancer was detected at screening in a 58 year old women. CONCLUSIONS: A randomised trial of ovarian cancer screening using ultrasonography and colour Doppler imaging is feasible and acceptable among women attending a breast cancer screening centre. The results indicate that the expected odds of being affected given a positive result in the general population would be about 1:12. A full randomised trial of ovarian cancer screening with mortality as the end point is needed to assess whether screening reduces mortality from this disease. A multicentre European trial is currently in progress.