Dear OncoLink "Ask The Experts,"
My father is currently being treated for advanced prostate cancer with a 10.8 mg depot of zoladex every 12 weeks. Is it essential that the renewal be given precisely within the 12 weeks indicated, or is it sufficient that the treatment be given roughly every three months?
Michael Vozniak, PharmD, BCOP, Hematology/Oncology Clinical Pharmacy Specialist, responds:
Pasted below is an abstract from the original study using the 3-month dosing. The precise timing of every 12 weeks on the nose is not necessary; however, I would not let it go longer than you have to, as it was not studied in this fashion. The information from the study (shown below) makes it seem as though you could wait several weeks longer, however your chances of having rising testosterone levels increase the longer you wait for another injection. Roughly, every 3 months is fine, but I could not find any precise data as to when the hormone levels begin to rebound.
European Urology. 1990;18 Suppl 3:22-5. A new longer-acting LHRH analog depot: preliminary results of a Dutch open phase II clinical study on a 10.8 mg Zoladex 3-monthly depot.Dijkman GA, Fernandez del Moral P, Plasman JW, Pull HC, van der Meijden AP, Debruyne FM, Hutchinson FG, Furr BJ. Department of Urology, St Ignatius Hospital, Breda, The Netherlands.
Abstract: A new longer-acting depot formulation containing 10.8 mg Zoladex was administered subcutaneously without anesthetic to 35 patients with advanced carcinoma of the prostate. Pharmacodynamic and pharmacokinetic data show that following a transient elevation in serum LH and testosterone, the levels of both hormones decrease. Serum testosterone reaches the castrate range in all patients by week 4 and remains at this level for at least 12 weeks. The serum Zoladex profile shows that castrate serum testosterone values can be sustained by very low serum concentrations of the drug of around 0.05 ng/ml. In this preliminary report, the efficacy and safety of this new longer-acting 3-month depot formulation of 10.8 mg Zoladex has been shown to be comparable to the 1-month depot formulation of 3.6 mg Zoladex, in patients with advanced carcinoma of the prostate.