How Does Immunotherapy Treat Prostate Cancer?

Immunotherapy in prostate cancer is becoming more prevalent because the treatment options are limited for patients with castrate-resistant prostate cancer, especially for patients who have not responded to docetaxel (Taxotere) therapy.

Impact of prostate cancer

Prostate cancer is a disease of older men for the most part. Few cases are diagnosed before the age of 50 with the median, or exact middle, age of diagnosed men being 67. The American Cancer Society estimates that there will be 235,000 new cases of prostate cancer in 2013 and nearly 30,000 men will die from the disease.

While the prognosis for most prostate cancers is generally good, the outlook for castrate-resistant prostate is not as promising. The 5-year survival for prostate cancers that have metastasized or spread to more distant parts of the body such as bones, lymph nodes, or other organs is 28%.

Treatment of castrate-resistant prostate cancer

Because of a survival benefit that was demonstrated in several clinical trials, docetaxel-based chemotherapy has been considered a first line option for patients with symptomatic castrate-resistant prostate cancer. The challenge has been what to do for patients who do not optimally respond to this treatment.

One option for these patients is immunotherapy. Basically, immunotherapy uses your body’s immune system to help identify and destroy the prostate cancer cells. Some currently available and investigational immunotherapies include:

  • Sipuleucel-T (Provenge): This was the first vaccine immunotherapy approved by the FDA for the treatment of castrate-resistant prostate cancer. This vaccine treatment improves the body’s ability to identify and attack prostate cancer cells.
  • PROSTVAC: This is an investigational immunotherapy that is currently undergoing clinical trials and is not yet FDA approved. This treatment targets the PSA antigen that is present in large quantities on prostate cancer cells. PROSTVAC mimics a normal viral infection and can induce a potent immune response towards the prostate cancer cells. Through a series of five injections over several months, the PROSTVAC immunotherapy helps your body identify and destroy the prostate cancer.
  • Ipilimumab: While this drug is currently marketed for the treatment of melanoma, it is still undergoing clinical trials for the treatment of castrate-resistant prostate cancer. This is a monoclonal antibody that turns off an inhibitory mechanism in your body that lets natural cancer-killing cells in your body called cytotoxic T lymphocytes work more effectively.

Immunotherapies are an emerging therapy that we do not yet totally understand. Ongoing research is examining how we might best use these therapies alone and in combination to improve the treatment for advanced prostate cancer.

Read more in our Prostate Cancer Health Center.

References

Berthold DR et al. Docetaxel plus prednisone or mitoxantrone plus prednisone for advanced prostate cancer: updated survival in the TAX 327 study. J Clin Oncol 2008;26:242–45.

Petrylak DP et al. Docetaxel and estramustine compared with mitoxantrone and prednisone for advanced refractory prostate cancer. N Engl J Med 2004; 351:1513–20.


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