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Provenge compared to Zytiga for treatment of metastatic prostate cancer has shown that both of these relatively new treatments can extend overall survival. This has led some men to ask whether they might be treated with both therapies. After all, combination treatment is a common approach for most cancers, including prostate cancer. Therefore, taking both Zytiga (abiraterone) and Provenge (sipuleucel-T) appears to be a possibility, especially since they work in different ways in the body.
But could Provenge compared to Zytiga involve differences that may prevent men from being treated with both therapies? First, some basic facts about each treatment options will help answer this question.
What is Provenge?
Provenge has been referred to as a prostate cancer vaccine because it stimulates the immune system, prompting a man’s body to fight the disease. The reason Provenge offers this unique approach, which no other prostate cancer treatments can do, is that each dose is specially made using each patient’s own immune cells.
To qualify for treatment with Provenge, men must have asymptomatic or minimally symptomatic (i.e., no cancer pain or pain that does not require narcotics) metastatic prostate cancer that has resisted hormone therapy. Men also cannot be taking steroids and must be steroid-free (for three to six months) before starting treatment, because steroids work against the immune system.
In clinical trials, Provenge improved overall survival. In a trial of 512 men, the median survival for the 341 men who took Provenge was 25.8 months compared with 21.7 months for the 171 men who took placebo, for a difference of 4.1 months. After three years, 37.8% more men who had taken Provenge were alive when compared with men in the placebo group.
What is Zytiga?
Zytiga also is unique because it is the only hormone therapy for prostate cancer drug currently available that can stop hormone production in all three sites: the testes, the adrenal glands, and the prostate tumor. Average treatment with Zytiga takes eight months.
When Zytiga was first approved by the FDA for treatment of metastatic prostate cancer resistant to hormone therapy and that had been treated with chemotherapy, it reportedly extended survival by a median of 3.9 months (from 14.8 months vs 10.9 months for placebo). In a post-approval study of Zytiga to determine its effectiveness in men not treated with chemotherapy, the study was stopped early by the drug’s maker (J&J) because it said the trial showed men lived longer when compared with placebo. However, the study did not show a statistically significant overall survival benefit, although one (9 months) was projected.
One feature about Zytiga is that men must take it with a steroid (prednisone). Steroids weaken the immune system and is a major reason why men cannot take both Zytiga and Provenge at the same time.
Using Both Provenge And Zytiga Separately For Prostate Cancer
But if taking Provenage and Zytiga simultaneously is not possible, could men take one treatment and follow it with the other?
One scenario would involve men taking Zytiga, stopping it for three to six months to rid their body of steroids, and then starting Provenge. Treatment with Zytiga takes eight months or longer, followed by three months of steroid washout. Since both Zytiga and Provenge are for men with advanced prostate cancer, and Provenge is only for men who are asymptomatic or who have minimal pain, there is a good chance the disease would progress in many men. That would make them ineligible for Provenge by the time they completed Zytiga treatment and the washout period.
The second scenario would involve taking Provenge first (treatment takes only 4 to 5 weeks), then Zytiga. This approach makes more sense, especially given that Provenge helps build up the immune system, which can prepare it for treatment with Zytiga.
Giving Provenge first is also advocated by a Journal of Clinical Oncology author, who stated that “if both agents are to be used, it seems reasonable to administer sipuleucel-T first with abiraterone after additional disease progression.”
Provenge Cost Compared to Zytiga Cost
One obstacle to using both therapies is cost. Provenge costs approximately $93,000 for the three required treatments. Studies indicate that doctors believe overall survival benefit from prostate cancer treatments should be longer than those seen in studies before they think they are worth the cost. For example, 86% of doctors surveyed said Provenge and other drugs that extend life should not cost more than $60,000, while 57% say the cost should be less than $30,000 and 19% want to see these drugs cost $10,000. (BioPharm)
Doctors are also concerned about reimbursement. According to the same survey, 68% of doctors said they don’t believe they will be reimbursed if they are required to buy Provenge before reimbursement. Although Medicare reportedly has been efficient in reimbursing doctors, other insurance providers cannot make the same claim.
Zytiga is not inexpensive either. At approximately $5,500 per month and with 18 months of treatment needed before a survival benefit is seen (plus the use of steroids). An additional cost concern with Zytiga is that patients require treatment over many months. Men who are on Medicare will go through the “donut hole” twice during Zytiga treatment, which means they must be prepared for high out-of-pocket costs. Provenge compared to Zytiga regarding cost yields sticker shock for both treatments.
Provenge Side Effects Compared to Zytiga Side Effects
Provenge compared to Zytiga when it comes to side effects and quality of life also need to be considered. Both Zytiga and Provenge are associated with significant side effects. Those affecting at least 10 percent of patients, according to clinical trial information, include:
- Zytiga: joint swelling (29.5%), swelling (26.7%), muscle pain (26.2%), diarrhea (17.6%), urinary tract infection (11.5%), and cough (10.6%).
- Provenge: chills (53.1%), fatigue (41.1%), fever (31.3%), back pain (29.6%), nausea (21.5%), joint ache (19.6%), headache (18.1%), vomiting (13.3%), anemia (12.5%), constipation (12.3%), pain (12.3%), dizziness (11.8%), and diarrhea (10.0%)
Provenge compared to Zytiga is one consideration for men with advanced prostate cancer who are reviewing treatment options. Men who are contemplating use of these therapies need to discuss the benefits and risks with their doctors, partner, insurer, and others who may have a significant effect on their decision.