low psa but prostate cancer

in one of my precepting sessions, the question came up about the utility of finasteride as well as the predictive accuracy of PSA screening.  finasteride does do well in decreasing prostate volume, though it takes months to work. but i wanted to circulate 2 important articles (both from the prostate cancer prevention trial), which i think sheds light on these issues.
1. prostate cancer prevention trial (see prostate ca prevention trial nejm 2003 in dropbox) -- 7 year study of 19K men >55yo, with PSA <3 and nl DRE, randomized to finasteride 5mg/d vs placebo. rationale of study is high prevalence of prostate cancer in men (17% lifetime risk). found that prostate cancer was reduced by the prophylactic administration of finasteride by 25% (24% in the placebo group, and 18% with finasteride). BUT, higher incidence of high-grade prostate cancer (Gleason scores 7-10) in the finasteride group (6.4%) vs the placebo group (5.1%).  also sexual side-effects of finasteride. but, bottom line, concern that there may be more high-grade, potentially lethal prostate cancers with finasteride.
2. prostate cancer in those with low PSAs (see prostate ca prevention trial nejm 2003 in dropbox) -- this looked at the placebo group at the end of the above 7 year study, where they did a prostate bx in 3K men in the placebo group who never had PSA>4 or abnl DRE. rather striking findings as follows:
-15.2% had prostate cancer, breakdown as follows:
    -psa <0.5, 6.6% with prostate cancer (!!!)
    -psa 0.6-1, 10%
    -psa 1.1-2, 17%
    -psa 2.1-3, 24%
    -psa 3.1-4, 27%
-of those who had prostate cancer, 15% of them had high grade cancers (Gleason 7-10), breakdown as follows:
    -psa <0.5, 12.5% of those in that psa group with cancer had high grade lesions
    -psa 3.1-4, 25% with high grade lesions.
bottom line, increasing psa is associated with more cancers and high-grade cancers, BUT psa is a pretty miserable test, does very poorly in terms of its sensitivity (and, if you lower the sensitivity to a cutpoint of 3 or 2, the number of biopsies done in the population increases dramatically and you still seem to miss a fair number of even high grade cancers).

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