CRPC

[MyDad76]

Might be a stupid question, but when is someone considered to have CRPC? For example my father was on bicalutamid 50mg for two years, when his PSA went up, they switched him to Eligard, which brought it down and at this point works for him. Is he considered to have CRPC since bicalutamid stopped working or is someone considered to have CRPC when he stops responding to any type of available hormone treatments?

[LearnAll]

Yes....My understanding is that when someone stops responding to a medicine (means PSA starts going up) ,it means the cancer cells have become resistant to THAT medication and a different medication is required now.

So ,Casodex has helped him for 2 years and now its times to switch to Lupron/eligard which the doctor did. Resistance to one medication does not mean resistance to all medicines.

Bicalutamide is an adrogen receptop blocker whereas Eligard is an androgen agonist...they have different mechanism of action. But both achieve the same goal.

When an individual's PSA and androgens can not be lowered with ALL androgen deprivation medicines...then only it can be called CRPC (castration resistance) in true sense.

[GP24]

Simple answer: you are resistant when your health insurance pays for Zytiga or Xtandi. This is when Eligard stops working.

[Db999 in reply to GP24]

Im considered castrate sensitive or castrate naive. I started ADT with Zytiga. So that wouldn’t be exactly correct ...

[Magnus1964]

You are castrate resistant when you have exhausted all ADT drugs.

[tango65]

Castration resistant is when PSA increases or there is evidence of progression of the cancer with castration levels of testosterone (below 50). If his PSA is going down with Eligard , his cancer is not castration resistant.

[pjoshea13]

There seems to be different interpretations here, but IMO being castrat-resistant simply means what it says. If gonad production has been halted biochemically or surgically, & the PSA is rising, one has CRPC.

Bicalutamide [Casodex] does not stop gonad production. It is an anti-androgen that targets the androgen receptor [AR]. {Enzalutamide [Xtandi] also targets the AR.}

Eligard (Lupron) targets the gonads. {Abiraterone [Xtandi] targets androgen production anywhere - including the gonads.}

The newer drugs have complicated things. The target continues to mostly be the AR axis - which means the prevention of androgen production or the prevention of androgens reaching the AR. One can have CRPC yet still respond to one or other of those drugs.

-Patrick

[pjoshea13 in reply to pjoshea13]

Note that the FDA approved, both, Abiraterone acetate [Zytiga] & Enzalutamide [Xtandi] for use in the treatment of metastatic castration-resistant prostate cancer (mCRPC) - because the clinical trials that led to approval used men with mCRPC.

i.e. the definition of CRPC does not require that Zytiga &/or Xtandi has failed.

CRPC means that classic-ADT has failed - i.e. a full orchiectomy or other interruption of androgen production by the gonads - with or without an androgen receptor antagonist.

-Patrick.

[Tall_Allen]

A person is castration-resistant when the cancer progressed in spite of chemical or physical castration. The cancer eventually adapts to feed on Casodex, so I don't think insurance would call it CRPC based on 50 mg Casodex alone.. When chemical castration no longer controls the cancer, second line hormonal agents usually still work.

[garythomas]

I have been on Lupron for five years. My PSA nadir was < 0.02. Over about one year it rose to 1.21 and my MO said I was castrate resistant. I had radiation to a pelvic lymph node and over about nine months PSA dropped to 0.22. My MO said I am still technically castrate resistant.

[Db999 in reply to garythomas]

See I wouldn’t agree based upon my knowledge (one of our true gurus chime In please )Just because lupron failed, if zytiga would of been added as an example and PSA dropped you would still be castrate sensitive. These drugs work the same but different . Now your doc chose a different modality to stop cancer, and I’m glad it worked, but that doesn’t mean you are castrate resistant. I think I got this right .