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Hi everyone,
I had triple treatment (Casodex as neo-adjuvant) then Single dose HDR Brachy, then short course of EBRT, followed by a further month of casodex. All this ended beginning of June. My first PSA was 2 weeks after coming off Casodex (150 mg): 0.24. Cue cautious celebration, but I suspected the hormones were still swirling around the system, artificially lowering PSA.
I just got my most recent PSA score: 0.45. Theoretically doubled, but from a very low base and now 2 months after stopping Casodex.
I'm not overly worried about the rise - I was told to expect it. But is it safe to assume the Casodex has left the building, or can I expect another rise yet?
I guess there's no real 'pattern' to any of this and that we're all experiments of one, but hope some of you can shed light on the influence post-treatment of Casodex on PSA.
Errr.....if the half life of Casodex is 37 days, then it is not clear of the system in 37x2=74 days. At 74 days there will be 25% of the Casodex still in circulation, as I understand the issue.
Terry is right about the half-life definition but it is listed as 5.8 days on rxlist dot com.
The drug can be effective for a lot longer depending on how it works. LHRH drugs like Zoladex start dropping in concentration in the blood within 3 days of the end of the drug going in to the bloodstream but it is effective over a very wide range of time from 3 months to permanent. I haven't seen any study on Casodex but it seems to work in a similar way but on the androgen receptors directly.
If the half life of Casodex is 5.8 days, then it will be down to 1% of its initial concentration after 6.5 half lives, or 37 days.
I have had no experience with Casodex, but 3 years ago I had a 10.8 mg (12 week) Zoladex implant for prostate volume reduction purposes. My PSA reached its minimum 12 months after the implant and I didn't regained my original PSA for another 15 months, that is a full 27 months after the implant.
Quite right, I got the figure wrong on the half-life. Should be 5.8 days
"On daily administration, the (R)-enantiomer accumulates about 10-fold in plasma, consistent with an elimination half-life of approximately 1 week."
So the 37 days is the correct figure.
For an anti-androgen withdrawal response ( seeing if psa will drop after stopping a round of Casodex ), up to eight weeks before testing is usually suggested.
OK, thanks guys. I think I followed that! If it's 37 days then it was comfortably out of my system. Even if it were 8 weeks, I'd almost be clear of it.
That said, I still have some swelling in the breasts, (though nothing like the do-I-get-a-sports-bra stage I was at) so perhaps the last traces are lingering?
