The presence of two relatively new treatments for metastatic prostate cancer--Zytiga (abiraterone) and Provenge (sipuleucel-T)--both of which have been shown to extend overall survival, has led some men to ask whether it is possible for them to be treated with both therapies. After all, combination treatment is common in the treatment of most cancers, including prostate cancer, and so taking both Zytiga and Provenge appears to be a possibility, especially since they work in different ways in the body.

But could it be that the differences between Zytiga and Provenge may be what prevents men from being treated with both therapies? First, some basic facts about each of these treatment options for advanced prostate cancer will help answer this question.

Provenge

For men to qualify for treatment with Provenge for prostate cancer, they must have asymptomatic or minimally symptomatic (i.e., no cancer pain or pain that does not require narcotics) metastatic prostate cancer that has been resistant to hormone therapy. They also cannot be taking steroids and must be steroid-free (for three to six months) before starting treatment. In other words, there can be no steroids in their body, because these drugs work against the immune system.

In clinical trials, Provenge has been shown to improve overall survival. In a trial of 512 men, for example, 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.

Zytiga

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 was reported to extend survival by a median of 3.9 months (from 14.8 months compared to 10.9 months for placebo patients). In a post-approval study of Zytiga to determine its effectiveness in men who have not been 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.

A critical feature about Zytiga is that men must take it along with a steroid (prednisone). Steroids weaken the immune system, which in turn makes users at great risk of developing infections as well as compromises their fight against cancer. Steroid use is a major reason why men cannot take both Zytiga and Provenge at the same time.

Taking Zytiga and Provenge Together?

One scenario would involve men taking Zytiga, stopping it for three to six months to rid their body of the steroids, and then starting Provenge. Treatment with Zytiga takes eight months or longer, which would be followed by three months of washout for the steroids. Since both Zytiga and Provenge are for men who have 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, making them no longer eligible 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 switching to 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 the approach 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."

Cost of Zytiga and Provenge

Doctors are also concerned about reimbursement for Provenge. 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), the total bill quickly adds up and can surpass the cost of Provenge. 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" portion of Medicare twice during Zytiga treatment, which means they must be prepared for high out-of-pocket costs.

Side Effects of Zytiga and Provenge

• 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%)