Advice on dosage for Abiraterone

[Ronnie7C]

Hi Folks,

Finished chemo (6 cycles) and ADT treatment, however, within period of less than 6 months PSA rising again. PSA on diagnosis was 76, after chemo had dropped to lowest level of 1.7 but then began rising and now at 5.6.

Oncologist is prescribing Abiraterone as 2nd line treatment now that I am castration resistant (mcrpc). Have read various info on taking 1000mg/day vs lower dosage of 250mg/day. Would really like to start off taking the lower dosage 250mg approach straight away in the hope it would offer the same efficacy and may lessen the side effects.. Would very much appreciate thoughts from anyone out there, on the pros & cons of both the standard and low dosage approaches .

Thanks.

[Tall_Allen]

The lower dose does NOT have the same efficacy. That was established a long time ago. If the standard dosage is a problem for you, you can try a less efficacious lower dosage.

[PhilipSZacarias]

Abiraterone is generally quite well tolerated at the standard dosage if 1000 mg without food. The side effects are significantly less compared to Enzalutamide. There are a few published papers you can find on Pubmed comparing the side effect profiles of these drugs. The only side effect I have experienced with abiraterone is elevated blood pressure which I managed by raising the dosage of prednisone from 5 to 7.5 mg. Cheers, Phil

[Ronnie7C in reply to PhilipSZacarias]

Thanks Phil. Great food for thought. Lots of things to consider. Also, I don't have insurance so have to pay for the drug myself. Taking a 250mg dosage instead of the 1000mg would also offer a considerable cost saving.

[PhilipSZacarias in reply to Ronnie7C]

Hello Ronnie, if you take abiraterone with food you can reduce the dosage by 25 to 50%. Personally, I alternate between 500 mg with food and 1000 mg without food but mostly I stay on the latter. I had a good response with 500 mg with food. You can find papers in pubmed regarding this topic. Cheers, Phil

[Ronnie7C in reply to PhilipSZacarias]

Thanks for all the responses to my post. Will start on 500mg per day and see what this achieves when i have my next blood tests on 19th April. Will keep you all posted.

[MateoBeach]

Personally, I would try a lower dose and find out if it is adequate in terms of PSA response as an indicator. Perhaps a middle-road of 500 per day. Alternatively, and more conservative, start with the full dose , let it stabilize (nadir) then test a lower and see. (If you get similar blood levels with low dose combined with food then I don’t see how it could be inferior.)

[Ronnie7C in reply to MateoBeach]

Thanks very much for your advice. If the dosage of Abiraterone was reduced to 500mg, should the dosage for Prednisone also be reduced?

[MateoBeach in reply to Ronnie7C]

The reduced dose of taken with light breakfast such as a low fat yogurt is said to produce the same blood levels and therefore effect. So the prednisone dose is not reduced.

[Ronnie7C in reply to MateoBeach]

Thanks for all the responses to my post. Have started on 500mg per day and following the light low fat breakfast suggested. Let's see what this achieves when I have my next blood tests on 19th April. Will keep you all posted.

[PhilipSZacarias in reply to Ronnie7C]

Probably not because the bioavailability of abiraterone increases with food which means the concentration in the blood is comparable to what it would be in the standard dosage (1000 mg, without food). I maintained the same dosage, 5 mg, until my blood pressure started going up which forced me to increase to 7.5 mg.

[treedown]

Lower dosage is taken with food higher without, it is believed to work out as the same but at a lower cost to some. I am in 750 due to low blood counts and my MO never made the decision to try the full 1000 again after they came back up. This has been approx 1yr at 750 and 6 months at 1000. I stopped for about a month during radiation.

[Ronnie7C in reply to treedown]

Thanks Freedom for your comments. I will do some more research on the topic but feel there is a very strong case for the lower dosage approach. Did you also lower your steroid (Prednisone) dosage?

[treedown in reply to Ronnie7C]

I personally take the amt recommended for hormone sensitive, non metastatic PC 5 mg once a day. As far as what the amt would be for the reduced dosage of Zytiga I would not be sure but suspect the same prescribed for the normal dosage.

[Ronnie7C in reply to treedown]

Thanks for all the responses to my post. Have started on 500mg per day and following the light low fat breakfast suggested. Taking this in addition to 5mg Prednisone twice daily. Let's see what this achieves when I have my next blood tests on 19th April. Will keep you all posted.

[treedown in reply to Ronnie7C]

I am glad you came to a decision and I hope you discussed with your Dr. I will note that the trial at the University of Chicago where they determined the amt to take with food determined 250mg to be the correct dosage. 500mg with good may result in higher than 1000mg dosage. I am not aware of additional studies on this. I decided not to do 250mg with food at the time because I read the lower dosage had more side effects. I have not done any reading since I made the decision so not sure if there have been any changes though I did notice when it was added to the NCCN Guidelines. Best wishes for success with your treatments. I remember the one phrase was the lower dosage was intended to avoid "cost toxicity".

[Bacana in reply to treedown]

What were the low blood counts that caused a reduction in dosage?

[treedown in reply to Bacana]

Low Lymphocytes, they dropped to 221.