Prostate-cancer mortality in the USA and UK in 1975–2004: an ecological study

Summary

Background

There is no conclusive evidence that screening based on serum prostate-specific antigen (PSA) tests decreases prostate-cancer mortality. Since its introduction in the USA around 1990, uptake of PSA testing has been rapid in the USA, but much less common in the UK. Our aim was to study trends over time in prostate-cancer mortality and incidence in the USA and UK in 1975–2004, and compare these patterns with trends in screening and treatment.

Methods

Joinpoint regression analysis of cancer-mortality statistics from Cancer Research UK (London, UK) and from the US National Cancer Institute Surveillance, Epidemiology and End Results (SEER) programme from 1975 to 2004 was used to estimate the annual percentage change in prostate-cancer mortality in both countries and the points in time when trends changed. The ratio of USA to UK age-adjusted prostate-cancer incidence was also assessed.

Findings

Age-specific and age-adjusted prostate-cancer mortality peaked in the early 1990s at almost identical rates in both countries, but age-adjusted mortality in the USA subsequently declined after 1994 by −4·17% (95% CI −4·34 to −3·99) each year, four-times the rate of decline in the UK after 1992 (−1·14% [−1·44 to −0·84]). The mortality decline in the USA was greatest and most sustained in patients aged 75 years or older (−5·32% [−8·23 to −2·32]), whereas death rates had plateaued in this age group in the UK by 2000. The mean ratio of USA to UK age-adjusted prostate-cancer incidence rates in 1975–2003 was 2·5, with a pronounced peak around the time that PSA testing was introduced in the USA. Numbers needed to treat to prevent one death from prostate cancer were 33 000 in the 55–64-year age group.

Interpretation

The striking decline in prostate-cancer mortality in the USA compared with the UK in 1994–2004 coincided with much higher uptake of PSA screening in the USA. Explanations for the different trends in mortality include the possibility of an early effect of initial screening rounds on men with more aggressive asymptomatic disease in the USA, different approaches to treatment in the two countries, and bias related to the misattribution of cause of death. Speculation over the role of screening will continue until evidence from randomised controlled trials is published.

Funding

ProMPT (Prostate Cancer: Mechanisms of Progression and Treatment) collaborative (UK National Cancer Research Institute, London, UK, and UK Medical Research Council, London, UK).