Upfront
The case for early detection and effective treatment for prostate cancer: 2 Analyzing Statistics
by
Ralph Valle

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Until recently, the benefit of screening for prostate cancer could not be proven. Now we have the positive results of the first randomized screening trial(3). This study, a well conducted randomized trial, clearly demonstrated a huge benefit in testing men with PSA and DRE as opposed to none.

Early detection, as demonstrated by Dr. Labrie's study, creates a definite stage shift at diagnosis, by which more and more, doctors are treating localized disease rather than disease that has escaped the prostate. This is indeed affecting survival and the mortality rate and not just introducing lead-time bias.

Lead-time bias can affect survival, but it does not lower the mortality rate. Early detection and effective treatment can affect both survival and the mortality rate.

Cancers detected through regular PSA testing are 77% to 98% clinically localized and 63% to 75% organ confined(5). During the last six years, the U.S. has experienced an unexplained decrease in prostate cancer mortality, the first in 30 years for a 6.7% reduction in the mortality rate. In comparison, European mortality rates continue to increase during the same period(14, 15).

The 5-year PSA-free survival rate for organ-confined PCa is 86% to 95% as compared to 78% for cancer with microscopic extraprostatic extension and 43% for those with seminal vesicle involvement(6). It is therefore very possible to extend survival by simply treating men before the disease escapes the prostate. If we add information such as the treatment results from The Lancet study, which showed a significant advantage to surgical treatment over conservative management for high grade PCa, we can be a bit more optimistic about the future of PCa and a reduction of the mortality rate (4).

Let us analyze some prostate cancer statistics. In the United States, 42% of men older than 50 will experience prostate cancer sometime during their lifetime. Some 9.5% will experience disease that causes problems and is considered clinically significant and 2.9% will die from the disease(7).

It is imperative to review the results of the U.S. screening protocols that have been performed during the last few years. The average rate of detection of most protocols has ranged from less than 1% to 3% (10). This is a very important issue, because detractors of testing with PSA and DRE claim that many insignificant cancers are detected and many of those cancers will never become clinically significant.

The reality is otherwise. If the disease prevalence really is so high, how do critics explain the inability of serialized PSA and DRE testing to detect all those cancers? The simple (and reliable) explanation is that these cancers are too small to be detected. What this means is, serial PSA/DRE detects mostly clinically significant cancer and only a few so-called histological cancers (too small to feel or to detect at all except through the blood test).

The U.S. male population over 50 years of age is around 30 million. If 42% of them do experience PCa in their lifetime, that represents a 12 million pool of men with PCa. At the screening peak, doctors were diagnosing 300,000 men a year with PCa, which represents a 2.5% detection rate and within the 1% to 3% detection rate range achieved with a formalized screening protocol. (10) This is a clear indication that testing with DRE and PSA does not detect many non-significant cancers, that is, cancers that do not require treatment.

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