Volume 176 - Issue 7
Mortality from prostate cancer is decreasing
Authors: Michael Coory and Peter Baade
Med J Aust 2002; 176 (7): 354-355. || doi: 10.5694/j.1326-5377.2002.tb04446.x
Published online: 1 April 2002
Published online: 1 April 2002
To the Editor: We conducted a joinpoint analysis of death certificate data on prostate cancer from the Australian Bureau of Statistics. Between 1979 and 1994, mortality rates increased by 2.1% per year (95% CI, 1.6% to 2.5%). However, between 1994 and 1999, mortality decreased by 4.2% per year (95% CI, – 5.8% to – 2.4%). The total decrease in mortality rates for the five years to 1999 (the most recent year for which data were available) was 22.6% (95% CI, – 32.9% to – 12.7%).
Joinpoint analysis is a statistical method that measures changing trends over time. It chooses the best-fitting points (called joinpoints) at which the rate of increase or decrease changes significantly.1 We did not look at the data and then choose 1994 as the start of the decreasing trend in prostate cancer mortality. The significant decrease since 1994 (and the consistent increase between 1979 and 1994) were identified by the joinpoint analysis.
Whether early diagnosis and treatment of prostate cancer subsequent to screening with prostate-specific antigen (PSA) tests can save lives is still an open question that is best answered by randomised-controlled, long term trials. Nevertheless, it is important that we try to understand the recent decrease in population-based mortality. The mortality decline started in 1995, about five years after PSA testing became widely available in Australia. The use of PSA testing increased dramatically, reaching a peak in most States in 1994 and 1995.2 In 1996, the Australian Health Technology Advisory Committee reviewed the evidence and recommended against screening.3 Since then, the number of PSA tests has decreased.2
Recent mortality declines have also been observed in the United States and the United Kingdom following increases in the use of PSA testing. The mortality decline in the US has been greater than that in the UK, coinciding with more PSA testing in the US than the UK.4
At least three questions arise from these observations:
Is it plausible that the decrease could be due to some factor other than PSA testing, such as better treatment?
How do we explain these results to men who want to make an informed choice about whether to be tested?
Is this type of evidence strong enough to warrant a change in the current recommendations on PSA testing?
References
- Kim HJ, Fay MP, Feuer EJ, Midthume DN. Permutation tests for joinpoint regression with application to cancer rates. Stat Med 2000; 19: 335-351.
- Smith DP, Armstrong BK. Prostate-specific antigen testing in Australia and association with prostate cancer incidence in New South Wales. Med J Aust 1998; 169: 17-20. i1146986
- Australian Health Technology Advisory Committee. Prostate cancer screening. Canberra: AGPS, 1996.
- Shibata A, Whittemore AS. Prostate cancer incidence and mortality in the United States and the United Kingdom. J Natl Cancer Inst 2001; 93: 1109-1110. i1146990
- Rothman KJ. Modern epidemiology. Boston: Little, Brown, 1986. CBBJHHAG
- Norrish AE, Jackson RT, Sharpe SJ, Skeaff CM. Prostate cancer and dietary carotenoids. Am J Epidemiol 2000; 151: 119-123. i1146993
- Volk RJ, Cass AR, Spann SJ. A randomized controlled trial of shared decision making for prostate cancer screening. Arch Fam Med 1999; 8: 333-340. i1146995
- Wolf AMD, Nasser JF, Wolf AM, Schorling JB. The impact of informed consent on patient interest in prostate-specific antigen screening. Arch Intern Med 1996; 156: 1333-1336. i1146997
- Gohagan JK, Prorok PC, Kramer BS, Cornett JE. Prostate cancer screening in the prostate lung colorectal and ovarian cancer screening trial of the National Cancer Institute. J Urol 1994; 152: 1905-1909. i1146999
- Schroder FH. The European Screening Study for prostate cancer. Can J Oncol 1994; 4 Suppl 1: 102-109. i1147001
- Labrie F, Candas B, Cusan L, et al. Diagnosis of advanced or non-curable prostate cancer can be practically eliminated by prostate-specific antigen. Urology 1996; 47: 212-217. CBBDBIDG
- Godley PA. Prostate cancer screening: promise and peril — a review. Cancer Detect Prev 1999; 23: 316-324. CBBGIJAH
- Friedrich MJ. Issues in prostate cancer screening. JAMA 1999; 281: 1573-1575. CBBJAJBA