Immunotherapy

Immunotherapy, sometimes called biologic therapy, treats the whole body by attempting to activate a person’s immune system so that it will destroy any prostate cancer cells within the body. Instead of attacking cancer cells directly, immunotherapy helps your body fight cancer. It uses materials either made by the body or in a lab to improve, target, or restore immune function. The different types of immunotherapies include vaccines, monoclonal antibodies, and non-specific immunotherapy.

There are two approved immunotherapies to treat metastatic prostate cancer.

Sipuleucel-T

Sipuleucel-T (Provenge®) is an immunotherapy vaccine treatment used in men with asymptomatic metastatic castration-resistant prostate cancer (mCRPC). Approximately 95% of prostate cancer cells express an antigen called prostatic acid phosphates, or PAP. Sipuleucel-T helps the immune cells recognize cells that display PAP and attack those cells.

The treatment personalization process involves:

• Drawing blood
• Extracting the white blood cells (immune cells) and sending them to a Dendreon Corporation facility
• At the lab, those immune cells (T cells) are activated to destroy prostate cancer cells
• The newly activated cells are returned and then infused into the individual three days later
• This infusion process is repeated every two weeks for a total of three treatments

The PROCEED study found that sipuleucel-T extends life in men with asymptomatic or minimally symptomatic (little to no pain) mCRPC. The PROCEED study also suggested that Black/African American men exhibit survival benefits compared with White men when treated with sipuleucel-T, especially at lower PSA values. Provenge is FDA-approved for men of any race with mCRPC.

Sipuleucel-T is usually given before chemotherapy, though it appears to be effective in some patients even after chemotherapy. Some data show that the greatest benefit is realized when it is used early - at a lower PSA level.

There are certain centers that provide this treatment. Talk to your doctor about whether sipuleucel-T is right for you, and if it is available in your area.

The most common side effects are flu-like symptoms that last one to three days after infusion.

Pembrolizumab

Pembrolizumab (Keytruda®) is a type of immune checkpoint inhibitor. It targets PD-1, a protein found on your immune cells (T cells). Pembrolizumab works by blocking PD-1 on your T cells, which boosts the immune system’s response to the prostate cancer cells.

Currently, Pembrolizumab is FDA-approved for patients whose cancer has:

• been shown by a lab test to be a microsatellite instability-high (MSI-H), mismatch repair deficient (dMMR), and/or high tumor mutational burden (TMB-H) cancer,
• progressed following treatment,
• and have no other satisfactory treatment options.

In other words, pembrolizumab is usually only considered after other available effective treatments for advanced prostate cancer have been used or ruled out.

A biomarker test is performed on a tissue sample from your prostate cancer biopsy or surgery to see if your tumor might be MSI-H, MMR deficient, and/or TMB-H. Studies suggest that about 3%–5% of metastatic prostate cancer patients have evidence of MSI, MMR mutations, and/or TMB-H in their tumors.

Keytruda is the first treatment approved by the FDA based on a biomarker and not on the tumor type. It is given intravenously (by IV) once every three weeks.

The most common side effects are fatigue, cough, shortness of breath, nausea, constipation, itching or rash, and decreased appetite. A rare but serious side effect can be an overactive immune response. These are typically treated by stopping use of the drug and, for some patients, starting steroids to suppress the immune reactions.