Wednesday, October 7, 2015
Is Switching From Vantas to Lupron or Zoladex Effective?
My father (83 years old) is being treated for advanced metastatic prostate cancer. He is receiving Casodex (bicalutamide) by mouth once daily, Zometa (zoledronic acid) IV every 6 weeks, and has a Vantas (histrelin) extended release intradermal implant. At ten months into therapy, he has responded well-- he is independent, asymptomatic, has no side effects from the medication, and has a PSA level of 0.58 ng/ml.
My father`s urologist has informed me that he is unwilling to put up with the reimbursement delays and bureaucratic red tape involved with procuring a replacement Vantas implant at the end of the current implant`s 1-year usable lifespan. He and his partners made a business decision, and will no longer administer any of the depot (long-acting) drugs, and will substitute an alternate monthly LHRF-agonist such as Lupron or Zoladex.
My instinct is to stay with the Vantas despite the uncertainties of getting reimbursed for this costly medication, since my father responded so well. However, the urologist assures me that the alternative medications are therapeutically equivalent, and a substitution will not jeopardize my father`s health.
I am having difficulty determining from other urologists whether there are any risks from switching to a once monthly type regimen from the yearly Vantas implant. I`d like to believe my father`s doctor, but this whole thing is obviously an expediency for his convenience; I don`t know if he is being truly candid. Are we sacrificing any efficacy or risking any other new side-effects by going to a once-a-month regimen?
All of these agents are equally effective and many are similar drugs that only differ in their form, allowing some to be long release and others not. There are agents that are administered at 3 and 4 month intervals, and I suggest you contact another urologist who should have them available for you.
Martin I Resnick, MD
Formerly, Professor of Urology
School of Medicine
Case Western Reserve University