Prostate Cancer Diagnosis And Treatment After The Introduction Of Prostate-Specific Antigen Screening: 1986-2005

Main Category: Prostate / Prostate Cancer
Also Included In: Preventive Medicine;  Cancer / Oncology;  Urology / Nephrology
Article Date: 30 Nov 2009 - 7:00 PDT

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UroToday.com - Screening and early detection should identify cancers that will become clinically relevant. In this case, the number of individuals diagnosed with cancer would be unaffected by screening. However, early detection can be associated increases in incidence, raising the question of over-diagnosis. Cancers that are found by over-diagnosis never progress to cause symptoms or death. In prostate cancer (CaP), randomized screening trials show an excess incidence in the screened group compared to control subjects. Excess incidence is considered a proxy for over-diagnosis as some of the excess may reflect the lead time of diagnosis. In the online edition of the Journal of the National Cancer Institute, Drs. H. Gilbert Welch and Peter Albertsen analyzed age-specific incidence trends during the past 20 years to quantify the impact of over-diagnosis.

The investigators selected a base year immediately before screening, calculated excess incidence in subsequent years relative to the base year, and transformed data on excess incidence to data on nationwide counts. Data from the SEER program was used. The base year was 1986, one year prior to the introduction of PSA. A 10% increase in the incidence of CaP in 1987 supports the notion that PSA screening was initiated. Excess incidence was calculated for 1987-2005 by subtracting the incidence in later years from that reported in 1986. Nine age groups were compared with regard to incidence, which were then combined into 5 age groups; 20-49 years, 50-59 years, 60-69 years, 70-79 years, and 80 years or older. It was necessary to determine the size of the male population for each year in order to transform excess incidence to counts. US Census data were used for this, and the year and age-specific excess incidence was multiplied by the year and age-specific population.

CaP incidence rose about 12% per year after 1986 and peaked in 1992. It then declined at 10% per year for a 3-year period. Although incidence stabilized for years 1995-2005, it overall increased 26% from 1986 to 2005. However for men over age 80 the incidence declined from 1986 to 2005, for men ages 70-79 is was stable, for men ages 60-69 it doubled, for men ages 50-59 it tripled and for men less than 50 years old it increased seven-fold. The authors estimate that in total, 1,305,600 men have been diagnosed with CaP since 1986. Furthermore, the authors estimate that 1,004,800 men have been treated with surgery or radiation for CaP since 1986. They conclude that 56,500 CaP deaths have been averted and that 23 men had to be diagnosed and 18 treated for each man experiencing a benefit from screening, diagnosis and treatment.

Welch HG, Albertsen PC

J Natl Cancer Inst. 2009 Aug 31. (Epub ahead of print)
10.1093/jnci/djp278

Written by UroToday.com
Contributing Editor Christopher P. Evans, MD, FACS

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