See my profile for more details. I've been on Casodex + Lupron + Zytiga for about 3 months. PSA is decreasing fast. During recent appointment, my oncologist said I can stop taking Casodex. I was a bit surprised because I've read that simultaneous Casodex (50mg tablet 1/d) and Lupron (injection 1/3 mo) is common. My oncologist said that, except to deal with flare, Casodex provides no benefit if you are also taking Zytiga. He mentioned that he was familiar with Zytiga trials, which demonstrated that. But he also implied that there was no particular harm in continuing Casodex for awhile.
Does anyone have any knowledge, experience, or opinions about this? I'm not sure what to do. Thanks in advance.
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Good to donate... THIS IS A GREAT CAUSE!!! Thank you...
Good Luck, Good Health and Good Humor.
j-o-h-n Saturday 04/27/2019 8:52 PM DST
From what I've read, Bicalutamide acts as an agonist with certain AR mutations as do other androgen blockers. This is from an article about Darolutamide which is showing promise in this area:
Bicalutamide was generally a weaker antagonist than the newer compounds. For AR modified at positions W742 or M896, agonistic activities of 90–100% or 50–60%, respectively, were observed upon treatment with 1 μM bicalutamide
Bicalutamide belongs to the same family of drugs (the lutamide family) as its big brothers Enza, Daro, and Apa. Same mechanism of action except that Enza, Daro and Apa are 5 to 10 times stronger.
Zytiga (Abiraterone, Abi) is a CYP17A1 inhibitor, whereas Casodex (Bicalutamide) is an antiandrogen. Intuitively, one would expect synergy, or at least additive benefit with slower progression to resistance.
Note that CYP17A1 is the enzyme that converts pregnenolone & progesterone to DHEA & androstenedione, respectively.
I was reading a new paper yesterday [1] on "A bypass mechanism of abiraterone-resistant prostate cancer: Accumulating CYP17A1 substrates activate androgen receptor signaling", which concludes with:
"Activation of the AR by clinically relevant levels of Preg {pregnenolone} and Prog {progesterone} accumulating in abiraterone-treated patients may act as a driver for CRPC. These data provide a scientific rationale for combining CYP17A1 inhibitors with antiandrogens, particularly in patients with overexpressed or mutated-AR."
From a 2015 paper [2]:
"The CYP17A1 inhibitor abiraterone markedly reduces androgen precursors and is thereby effective in castration-resistant prostate cancer (CRPC). However, abiraterone increases progesterone, which can activate certain mutant androgen receptors (AR) ..." "Therefore, we sought to determine if CYP17A1 inhibitor treatment selects for progesterone-activated mutant ARs."
...
"These findings indicate that selection for tumor cells expressing progesterone-activated mutant ARs is a mechanism of resistance to CYP17A1 inhibition."
It's true that Casodex has the downside that with resistance, it can change from an AR antagonist to an AR agonist. Zytiga (Enzalutamide, Enz) is a newer antiandrogen that does not have that disadvantage. It is well-known that sequential use of Abi+Enz or Enz+Abi can be disappointing, due to shared resistance, but how about Abi & Enz together? Good luck with insurance. & combined side effects might be harsh, however:
From a recent paper [3]:
"In this phase II trial, we evaluate neoadjuvant enzalutamide and leuprolide (EL) with or without abiraterone and prednisone (ELAP) before radical prostatectomy (RP) in men with locally advanced prostate cancer."
"Seventy-five patients were enrolled at four centers. ... The pathologic complete response or minimal residual disease rate was 30% (n = 15 of 50) in ELAP-treated patients and 16% (n = four of 25) in EL-treated patients"
You asked: "Does anyone have any knowledge, experience, or opinions about this?" My opinions are such that I would resist efforts to halt the Casodex. But that's not advice, of course.
pjoshea13: Thank you very much for your comprehensive reply. You should send me a consulting invoice for that. As a newbie, I understand most but not all of the terms and study summary explanations. But be assured that I'm motivated to look things up and learn more.
My MO switched me Zytiga + Pred after nine months on Casodex. No particular reason... I was responding well to the Casodex, but the presumption was/is that the Z + P was a more aggressive treatment - even though there are not much data for those meds with hormone sensitive and a few mets (the studies were primarily multiple mets). My MO stopped the Casodex because he said doing all the meds was too much toxicity and unecessary.
Using both Zytiga nad Casodex may be better. I don't know. My MO is at Dana Farber and pretty much by the book. I also got an opinion form an MO at Johns Hopkins and he said no reason to continue Casodex when on Z + P.
Just some antidotal evidence on the effectiveness of Casodex and Zytiga.... started C first, after 3 weeks, PSA dropped from 33 to 21, almost no SE’s at all. Added Z, after two weeks, PSA dropped dramatically from 21 to 4.5. T < 10, ALT/AST elevated moderately, and RBC/WBC counts down slightly, feeling full effects of AD. Adding Lupron next week.
I have posted this before. No surgery, no radiation, no local therapy of any type. Diagnosed 2005, G9 several samples. PSA from 2005 climbed from 5 plus at diagnosis to 70 in mid 2017. QOL was as though no PCA at all.
Next PSA in 9-17,,,working from memory,,,was 260 and had bone lymph mets on scans.
6 weeks later PSA was 374 the day I began Xtandi monotherapy. Over next 3 months PSA was at less than 10. Cut back to 1/2 dosage of daily dosage because of SE’s of fatigue. PSA next couple of months climbed to 18.
MO sweet talked me into Taxotere. 6 sessions plus back to std dose of 4 pills per day of Xtandi at first infusion. PSA at 3 After 6 Infusions Basically an abject failure of Taxotere,,,I attributed PSA falling to 3 was result of going back on full 4 pill daily dose if Xtandi.
PSA then began to climb after 15 months on Xtandi mono, reaching a PSADT of 5 weeks. Finally agreed to Lupron. Never slowed PSADT a wit. Testosterone on 1/2 normal monthly injection of Lupron fell to 8 where it remained over next couple of injections. Went thru 3 sessions of Cabazitaxel,,,,PSADT did not slow at all.
Cancelled Lupron injections as they were doing nothing fruitful,,,,however while doing their normal destructive devices to the balance of my 79 year of age very healthy,,except for PCa,,,carcass
So now at PSA of 400 plus in a few months. UCSF continued to kick down the road my almost assured LU 177 trial,,,,long sordid story that I will cover one day in detail
So now PSA at over 400 and likely 900 next month. Told 3 Mo’s I wanted to try Casodex as I had convinced myself, no one else, that its resistance mechanism was different than AR inhibitors such as Xtandi, Zytiga etc and Casodex was worth a shot
Was assured by all 3 Mo’s that this was a false assumption, however persuaded one to give me script for 3 daily,,,150mg
First follow up PSA several weeks,,,4 or 5,,,PSA was 163. Went to a single 50mg pill a day,,,fatigue again,,,PSA a month later was 152. Previous to casodex experiment and if never invoked should have been 1,500 plus,,,if history is any guide.
PSA on one 50 mg pill daily however began to climb,,,but the approved for Darolutimide. Currently on that and Indomethicin,,,PSA has fallen on 2 tests and up on one. Have been unable obtain niclosamide. Turned down by UC Davis trial. So carrying on with my own trials. Oh yes,,,I am AR-V7 negative. Had this test immediately after failing Xtandi and Lupron. Hoping that Indomethicin does it theorized reset.
Still waiting for lu177 if it should ever happens.
Just completed 3 rounds of SBRT radiation, hoping for an abscopal kick.
My husband’s urologist initially put him on bicalutamide (Casodex) to get the ball rolling after his diagnosis. Also had his first Eligard shot. He said once he met with the medical oncologist, he would then be put on a 2nd generation hormone blocker and would then discontinue the Casodex. He’s been on Zytiga and prednisone ever since.
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