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Advanced Prostate Cancer
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Psa down on no intervention

We are awaiting trial approval for Xtandi and my dad’s psa went down from 12 to 5. He’s been off of Zytiga for a month. Is this unusual? Labs are good. No new spots. Two very small spots on lung that they don’t believe has anything to do with prostate cancer. Has anyone had this experience with psa going down without secondary drug intervention?

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There is something called a "withdrawal response" which can occur after the discontinuation of Zytiga. Here's an article about it:

ascopubs.org/doi/abs/10.120...

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Thank you. You’re always so helpful

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My husband just experienced the same thing when he stopped Xtandi for 5 weeks due to cognitive SE concerns.

No other treatment started and it dropped from 9 to 7.8.

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Is he continuing therapy or on hold?

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He restarted Xtandi about 10 days ago on the advice of his neurologist who felt the cognitive issues unrelated to Xtandi. She, not his MO encouraged restart. He has not tried Zytega yet.

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Hello Stumpgirl,

That is great news! Happy for you and your dad.

When I stopped Zytiga my PSA continued to rise (doubling) for a couple months. I then started Xofigo and the PSA stopped rising and actually dropped a little.

I am not sure if the drop was due to the Xofigo (as Xofigo does not normally help with one's PSA) or if the drop was due to something else.

Take Care, Monty

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With my xtandi experience, I learned it takes 28 days at a given dose to reach equilibrium in your body after dosage change and at least 77 days to clear out after stopping. Thus it is still active and working for weeks after you cut dose or quit. Helps explain PSA still dropping.

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Hi Shooter1 can you reference your data? I’d like to read it. Thx

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I got Drs portion of info sheet with one of my mailed perscription refills. Not just the patient portion. 8 columns of fine print instead of one column of large print.

Called pharmacist and he confirmed.

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When Zytiga stopped working for me recently, my PSA went up from 4.3 to 17.1 pretty quickly, but now on new clinical trial. Don't know if that is relevant for you.

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His psa was climbing on Zytiga and he was determined castrate resistant . He went from .01 to .5 to 7 to 15 . They took him off of Zytiga and prednisone to begin a clinical trial on Xtandi. His scans showed one new spot but several others stable or improved . Then suddenly his psa went down to 6. I’m wondering if they should monitor or continue onto Xtandi . He’s supposed to start Monday

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No! If zytiga works why not continue. Also if zytiga works xtandi should. In my case neither worked. I most likely have ARV7 in which case Jevtana works very well. Good luck.

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My husband had withdrawal responses to both Casodex and Zytiga but not to Ketoconazole or Xtandi. The responses at best lasted only 6 months. I wouldn't consider it a treatment. Similarly, starting Docetaxel caused a rise in PSA followed by a slow drop to a nadir that never reached 50%. It is no longer working after 15 months. We are in the middle of re-staging imaging. The genetic tests came back with no actionable genes or mutations. Still waiting for the biopsy results from the lesion on his pancreas.

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Best wishes for a successful treatment plan and prayers for strength for you as you support your husband on his journey

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