MedWire News: The lowest level of testosterone castration that has clinical significance in patients with prostate cancer who have been medically castrated is 32 ng/dl, Spanish researchers report.
Increases above this value predict lower androgen-independent progression-free survival, they say.
Several synthetic luteinizing hormone-releasing hormone agonists have been developed and tested in recent years for chemical castration in patients with prostate cancer. They have been found to be as effective as bilateral orchidectomy, explain Anna Orsola and colleagues from the Autonoma University of Barcelona School of Medicine.
To calculate the testosterone castration level with clinical relevance in prostate cancer patients receiving continuous androgen deprivation therapy, the team studied 73 patients with nonmetastatic prostate cancer treated with medical castration, 38.4% of whom were also given bicalutamide. Serum testosterone levels were measured three times in 6 months.
Over an average follow-up of 51 months, 41 androgen-independent progression events were identified, and these were correlated with breakthrough increases in testosterone levels of 50 ng/dl, which is the traditional threshold value, and 20 ng/dl, which is the surgical castration threshold level.
At all points of measurement, testosterone levels were less than 20 ng/dl in 43.6% of the patients. Increases in testosterone levels of between 20 ng/dl and 50 ng/dl were seen in 31.5% of the patients, while 24.7% experienced increases of more than 50 ng/dl.
The team calculated that the lowest testosterone level that had a significant impact on androgen-independent progression-free survival was 32 ng/dl, with average androgen-independent progression-free survival times of 88 months in patients with breakthrough increases of more than 32 ng/dl, compared with 137 months in those with lower increases.
Although patients receiving maximal androgen blockade had similar incidences of testosterone increases to those seen in other patients, androgen-independent progression-free survival was significantly longer among patients with breakthrough increases of more than 50 ng/dl who were treated with maximal androgen blockade, than among those who were not.
The team concludes: "Because physicians today are not routinely evaluating the testosterone level when initiating and following androgen deprivation therapy, we suggest that routine measurement of serum testosterone should become part of clinical practice when evaluating the effects of hormone therapy.
"A reasonable option to detect these breakthrough increases would be to monitor testosterone levels as prostate-specific antigen determination."
The research is published in the Journal of Urology.
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