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Encore: Correction of Free Testosterone post


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Jim was wrong once more.

He typed "free PSA" (an important risk factor for developing prostate cancer) instead of "free testosterone" in the original posting.

(Thanks to the diligence of Treasurer Alan Barlee.)


Jim has fixed the original article:

Checking free testosterone may be a better guide to how well hormone therapy is working than total testosterone


and copied  it  below: 



Jim Marshall (not a doctor) said ...

Checking free testosterone may be a better guide to how well hormone therapy is working than total testosterone.

When prostate cancer becomes castrate resistant, that signals a new type of treatment.

So it is important to be sure that the rising PSA is due to castrate resistance, and not due to the presence of testosterone because the hormone treatment is not strong enough (as it is for a small percentage of men).



So, doctors (though not all) check testosterone as well as PSA to be sure.
This paper points out that it is possibly better to check free testosterone than total testosterone to make sure the hormone treatment is working.
Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). Testosterone that is not bound to SHBG is called "free testosterone".


Note that this is guidance for the future research only. There are no currently no guidelines for appropriate levels of free testosterone to ensure hormone therapy is working.

... end Jim

This abstract is only available for 24 hours for members to get an email.
After 24 hours the abstract will only be available through the link to the ASCO site below.

The free hormone hypothesis: Correlation of decreases in PSA with free testosterone rather than total testosterone in men with advanced prostate cancer treated with GTx-758.



Prostate Cancer

Session Type and Session Title: 

This abstract will not be presented at the 2013 ASCO Annual Meeting but has been published in conjunction with the meeting.

Abstract Number: 



J Clin Oncol 31, 2013 (suppl; abstr e16015)


Alvin M. Matsumoto, Robert H. Getzenberg, Christopher Coss, Michael L. Hancock, Xuemei Si, James T. Dalton, Mitchell S. Steiner; Geriatric Research, Education and Clinical Center (GRECC), VA Puget Sound Health Care System and Department of Medicine, Division of Gerontology & Geriatric Medicine, University of Washington, Seattle, WA; GTx, Inc., Memphis, TN; GTx Inc, Memphis, TN

Background: Androgen deprivation therapy (ADT) improves disease-free survival but disease progression is related, in part, to ineffective castration. The free hormone hypothesis states that the biological activity of steroid hormones is affected by its unbound (free) rather than its protein-bound concentration. Serum total testosterone (T) concentrations predominantly reflect the T bound to plasma proteins and do not accurately predict prostatic levels of T. Methods: In a Phase II study (G200705), men with advanced prostate cancer (n=159) were randomized to receive 1000 mg or 2000 mg GTx-758 daily or leuprolide as their initial ADT. Serum total T (mass spectrometry), free T (equilibrium dialysis), SHBG and PSA concentrations were measured. A second Phase II study (G20007) was performed in men (n=9) with CRPC who then received GTx-758 2000 mg daily. Results: Although both treatments reduced serum total T levels to < 50 ng/dL, leuprolide decreased them to a greater extent. However, GTx-758 caused greater reductions in serum PSA, suggesting that total T concentrations did not accurately reflect the suppression of androgen activity. Both dosages of GTx-758 reduced free T levels to a greater extent (mean of 0.7 and 0.4 pg/ml at day 60, and 0.4 and 0.4 pg/ml on day 90, respectively) than leuprolide (mean of 1.4 pg/ml on day 60 and 1.4 pg/ml on day 90; p values <0.03). Similar clinical results were observed in CRPC patients where GTx-758 daily resulted in a 71% decrease in %free T and clinically relevant PSA reductions in men maintained on ADT with LHRH agonists. As a result of adverse events at higher doses of GTx-758, the trial was stopped early. Conclusions: The ERα agonist, GTx-758, reduced the biologically active form of T, free T, to significantly lower levels than leuprolide. Reductions in PSA appeared to be more highly associated with changes in free T. These data provide compelling evidence to support the free hormone hypothesis and suggest that serum free T concentrations would provide a better measure of therapeutic efficacy in ADT than total T. A Phase II clinical trial utilizing lower doses of GTx-758 (G200712) is currently being performed. Clinical trial information: NCT01326312.zzz

This extract was published in association with the American Society of Clinical Oncology 2013 annual conference. Though the research behind it may have been excellent, your doctor cannot yet give much weight to it for a number of reasons, including:

  • It is only an extract. The full paper may reveal information important for your treatment.
  • The study has not yet had peer review - with doctors and researchers scrutinising the study closely for mistakes and limitations after it is published in a professional journal.
  •  Your doctor may already be aware of a limitations of the findings because of their wider reading.

The link below is to a page or document that we do not control.
Parts of it may be wrong or misleading.
Check with your doctor if something interests you.
If it is temporarily or permanently unavailable, you may receive an error message.

Source URL: http://meetinglibrary.asco.org/content/117793-132





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