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Finasteride, PSA doubling time, and intermittent hormone therapy

Posted Jul 07 2010 12:00am

For years, some clinicians have been telling their patients to use a 5α-reductase inhibitors (5-ARIs) like finasteride or dutasteride as a form of “bridge” therapy to extend their periods of time off primary hormone therapy while being treated with intermittent hormone therapy or IHT.

The problem has always been that there are very few clinical data to support this recommendation, and there are still very few, but a new paper by Locke and Bruchovsky has added somewhat to our knowledge.

Although there are data suggesting the value of 5-ARIs in management of patients on IHT, it has been far from clear how the 5-ARIs might be producing this effect. In the present study, Locke and Bruchovsky followed just six patients who were being treated with IHT for periods of between 7 and 10 years. They conducted PSA tests in each of the six patients on a monthly basis throughout at least one off cycle of IHT, and used these data to calculate the patients’ PSA doubling times during these off cycles.

Based on these data, they make the following assertions:

  • That administration of finasteride was associated with a reduction in the rate of increase of serum PSA in the off-treatment period of any given cycle within a sequence of 5 cycles in total.
  • In a total of 15 cycles, finasteride extended PSA doubling time from a mean of 7.7 weeks (n = 11, range, 2.3 to 29.8 weeks) to a mean of 45.1 weeks (n = 6; range, 13.8 to 99.7 weeks).
  • One patient was characterized by an apparent pseudo-resistance to finasteride in the second cycle of treatment.
  • Another patient was characterized by complete resistance to finasteride in the fourth cycle of treatment.

They conclude that, “Finasteride can be introduced into any cycle of intermittent androgen suppression with the expectation of an extension of PSA doubling time.”

Now The “New” Prostate Cancer InfoLink would like to be able to clarify the value of 5-ARIs in the off-hormone periods of IHT as much as the next guy, and we do find Locke and Bruchovsky’s data interesting. But we have a hard time with their conclusion which all but suggests that every patient on IHT should be receiving finasteride during every off-homone period: 

  • This is a tiny study, in which the patients appear to have been used as their own controls, but what is the standard baseline against we are comparing the PSA doubling time while the patients were on only finasteride.
  • The range of the PSA doubling times observed among these 6 patients is huge; to claim that finasteride therapy extended the mean PSA doubling time from 7.7 weeks to nearly a year based only on these data seems to be a tad assertive.
  • The abstract of the paper gives us no information to suggest that all six patients were receiving the same form of hormone therapy, that they had started out with similar clinical profiles, and that there were no other significant differences between them.

So, for The “New” Prostate Cancer InfoLink, this paper provides a tiny amount of additional information that is suggestive for a role for 5-ARIs in IHT, but we would like to see a far more robust set of data before we would want to draw the conclusion offered by Locke and Buchovsky.

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