The standard dose of abiraterone acetate (Zytiga) is 1,000 mg. taken on an empty stomach, however, when just 250 mgs are taken with food, it seems that for many men this lower dosage has the same activity as Zytiga at 1,000 mg without food.
Dosing is established as a part of the FDA label and is based solely on the clinical trials that are relied upon for their approval. In the case of Zytiga, all the Phase III trials used 1,000 mgs. on an empty stomach, thus the label dosage is 1,000 mg. on an empty stomach.
In a newly reported prospective, randomized, Phase II study of low-dose Zytiga taken along with a low-fat breakfast, Szmulewitz et al. reported that the lower dose with food was comparable to the higher dose without food. Their trial was small, including only 72 men with 36 men being randomized to the low-dose arm with food and 36 to the standard-dose arm without food.
They reported that the actual impact of the lower dose Zytiga was more significant on overall PSA response rates! The median progression-free survival rates at nine months were the same, the decrease of androgen levels was similar in both groups, serum concentrations of the Zytiga were greater in the men treated with the 1,000 mgs, and there were indications that the side effect profile was better in the men who had the lower doses.
Further evaluation of this paper’s findings needs to be undertaken immediately. If we can offer Zytiga at a lower dose, we might be able to reduce both the side effects and the cost of the treatment.
At this time, Cancer ABCs can not recommend that any man with castrate resistant prostate cancer who is taking or considering taking Zytiga just cut back their dose and add food. A serious and extended conversation with your doctor about this finding might be a good idea.
Joel T Nowak