Friday, May 15, 2009

Prostate Cancer: Knowns and Unknowns

Prostate cancer is one of the (too many) fields of medicine where there is more heat than light, and more data than verified theories, and very few reproducible facts. I shall begin by listing what are , in my opinion, mutually agreed-upon facts. And please remember, that if there is argument in the refereed journals about the interpretation of facts, then there is no agreed-upon interpretation. Also, this blog is for both doctors and patients, so please bear with me if some of the data is well-known to you.

1) Only men get prostate cancer.

2)Eunuchs never get prostate cancer.

3) One treatment that slows down the progression of metastatic prostate cancer is androgen reduction and/or blocking its actions.

4) Yet, giving a man with low testosterone androgen supplements does not increase his risk of getting prostate cancer.

5)Sexual activity, whether heterosexual intercourse, homosexual intercourse, or masturbation does not seem to affect the incidence of prostate cancer (although some husbands tell their wives that it is a sure preventative).

6) If your father had prostate cancer, this increases your risk of getting prostate cancer.

7) There is no known dietary preventative, but the data does get twisted. For instance, one popular theory was that lycopenes in vegetables reduces the incidence of prostate cancer. A large dietary study seemed to indicate that both tomato and strawberry ingestion reduced the risk of prostate cancer. Yet, because tomatoes have lycopenes and strawberries do not, the authors of the studies immediately stated in their conclusion that strawberries had to be a statistical error, because it contained no lycopenes. This happens all too often in medical "science", where an inconvenient piece of data is "assumed away" because it does not fit the theory. In physics, we try to explain anomalous data, or re-investigate it (the advance of the perihelion of Mercury, atomic spectral lines, the black body catastrophe, etc.). In medicine it is ignored, so we never have "a beautiful theory ruined by an ugly fact".

8) There is no convincing evidence that surgery is superior to radiation therapy, and little evidence that either is superior to "watchful waiting". Yet in the newspaper reports of Mayor Giuliani's prostate cancer, watchful waiting was never mentioned as a possibility by any of the news articles, thereby planting a false impression of the "proper" treatment in non-medical readers. It has been my experience that only single men choose watchful waiting; a wife seems to be psychologically incapable of letting an untreated cancer stay in her husband.

9)THERE IS NO INCONTROVERTIBLE EVIDENCE THAT EARLY DETECTION AND TREATMENT EXTEND LIFE EXPECTANCY. If you look at the recommendations of the USPHS, vs Canadian HS, vs. AMA, vs. ACP, vs. Am. Urological Assn., you of course get differing opinions, much as urologists overwhelmingly recomment surgery, and radiation oncologists overwhelmingly recommend radiation. We internists are supposed to lay out all the data for the patient, and let him decide.

10) Proscar, aka finasteride, which blocks adrogen action on the prostate, reduces the incidence of prostate cancer, but then the cancer that does occur is more aggressive.

11) Under "first, do no harm", my inclination is against drawing PSA levels, but if there is a familoy history and the man's father died from prostate cancer, he generally wants to know.

12) Let me throw out a question to the doctors in the audience: We know that having had cancer is a risk factor for DVT. If a patient who has been treated for prostate cancer develops a DVT, should one assume that the cancer has recurred, and search aggressively for its spread?

1 comment:

  1. In the May 17, 2011 issue of the Journal of Cancer research there was an article that suggested that men who drink regular coffee (? up to 6 cups/day) appear to have reduced their risk of prostate cancer.