PSA AND PROSTATE CANCER: THE PLCO STUDY
This is another salvo in the argument about whether treatment for prostate cancer has any effect on long-term survival. Critics have stated, loudly, that “there is no evidence that definitive treatment of localized prostate cancer increases survival.” However, there has been no large, well-designed study to evaluate the effectiveness of early prostate cancer treatment in prolonging lives. Moreover, there’s no evidence that definitive treatment does not increase survival! The issue has never been properly investigated.
The PLCO study hopes to answer the question. This is a massive, multimillion-dollar study, sponsored by the National Cancer Institute, involving prostate, lung, colon and ovarian cancers. (Thus the name, PLCO.) For prostate cancer, the point is to determine whether or not screening makes a difference in life expectancy. (This also has a lot to do with the controversy surrounding the PSA test’s effectiveness—see “The Heated Debate,” earlier in this chapter.) Men will be screened once a year for four years, and then followed for twelve years. This is similar to the screening intervals used in a study to determine mammography’s effectiveness in spotting breast cancer. However, prostate cancer is much slower-growing than breast cancer, and some doctors worry that four years isn’t going to be long enough for PSA’s yearly rate of change to be as meaningful as it has the potential to be.
Another worry is that the screening won’t be done in the best possible way up front, and thus the follow-up, which will be expensive, will be worthless. The problem is that we don’t know how best to use PSA yet. Is PSA density the way to go? PSA velocity or age-specific ranges? Scientists just don’t know. So initiating a long-term study now appears, to some investigators, to be premature.
Also, in this study, treatment is up in the air—once a diagnosis is made, the treatment choice is left up to the patient and his physician. So how can we know if PSA makes a difference in life expectancy if a man dies because he opts for no treatment or an ineffective treatment? And finally, the age range for the study is not meaningful; it includes men up to age 74. The unfortunate fact is that many of these men probably won’t be alive to see the end of the twelve-year follow-up period. It is unlikely, then, that they will live long enough to provide any new insights into the long-term effectiveness of treatment.
So it seems a shame that this massive study, which taxpayers are funding, is proceeding without a more thoughtful design.
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