Castrate testosterone values in different prostate cancer studies

Serum testosterone value around 1.735 nmol/l or 50 ng/dl as castrate level for the purpose of hormonal treatment of prostate cancer was used already in 1970'ties [2]. Later, some LHRH formulations were designed to achieve serum testosterone below this value in 95% of treated patients. It was accepted as standard value in guidelines [50]. Guidelines have at present gone even a step further and stated testosterone levels above 50 ng/dl to be in-sufficient and additional hormonal manipulation to be warranted in such patients [3]. It is further generally accepted patients with surgical castration to have lower levels of testosterone - around 15 ng/dl and certainly below 30 ng/dl [51]. As surgical castration provides lower testosterone levels, there were always claims one should aim as low as possible with testosterone levels and should try to reach below 20 ng/dl - for example in a small study of 38 patients, treated with LHRH agonists, Oefelein found 5% did not reach values below 50 ng/dl and 13% did not reach values below 20 ng/dl [52]. This movement, which aims to decrease castrate testosterone level, was further supported by publication which claims patients with castrate testosterone levels below 32 ng/dl (1.1 nmol/l) - Morote's value - to have longer time to biochemical progression [9]. In their study, which also used chemiluminescent antibody testosterone assay, in 25% of patients testosterone levels above 50 ng/dl were identified. Further, with serial measurements, 55% of patients on chemical castration had testosterone values found above 20 ng/dl [8]. Studies which use HPLC/MS/MS for determination of testosterone levels do see lower values [53].

Some studies seem to oversee guidelines and post their own castrate testosterone levels, which are significantly higher and set to a value which offers approximately 95% successful castration. In their article on testosterone escape, group from Norway claims their castration level is 2.8 nmol/l which equals 81 ng/dl [6]. This value was selected as their laboratory's upper normal limit for women. And with this value, they identified 10% of patients who failed to reach this castration level. The present study was similar to this in testing patient's serum for testosterone at the end of 3 month dosing interval, which may also influence results.

Another group from Turkey, which evaluated influence of androgen deprivation therapy on hand function in 2008 article used radioimmunoassay for testosterone measurement and in a castrate group mean value of testosterone was 52 ng/dl +- 35 ng/dl [54]. One can assume for approximately half of their patients testosterone levels were not in castrate area according to guidelines. Surgical castration study, using chemiluminescent assay, found values up to or above 50 ng/dl for surgically castrated patients [55]. Further surgical castration study found patients on LHRH treatment before surgical castration to have values above 50 ng/dl in 28% of patients and after surgical castration in up to 8% [56]. Unfortunately method of testosterone measurement is not stated in this article, but it correlates perfectly with data presented here, where chemiluminescent method was used. Further, recent LHRH agonists report from Canada, which also used "competitive immunoassay using direct chemiluminescent technology" [57], found median testosterone values for different LHRH agonists to be (in nmol/l) 1.2, 1.3, 1.1 and 1.3 and in two of five formulations, upper quartal value was 1.8, indicating 25% of patients on particular formulation to be even above "old" castration value of 1.72 nmol/l (50 ng/dl). Another study from Canada, also using chemiluminescent immunoassays, although claiming they were "newer technology", indicates risk for breakthrough levels of serum testosterone (value measured higher than castrate value) in patients on LHRH agonist injections to be 5.4% and 2.2% (for castration values 1.1 nmol/l and 1.7 nmol/l, respectively) per each LHRH injection [58]! Cancer control was claimed to be inferior in patients with breakthroughs of serum testosterone measured [58].

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