A new prostate cancer vaccine may give hope to men with metastatic prostate cancer by enabling their immune systems to fight the disease. Researchers from the University of Iowa presented data on the adenovirus/PSA (Ad/PSA) vaccine during the Annual Scientific Meeting of the American Urological Association in Orlando.
In recent years, the concept of vaccine immunotherapy for advanced prostate cancer has become increasingly high profile as research has expanded. Major advances in the field have contributed significantly to the discussion of this important cancer therapy as researchers explore new ways to prolong survival and improve the quality of life in patients with metastatic disease.
Prostate cancer cells produce a protein known as prostate-specific antigen (PSA). The goal of immunotherapy for metastatic disease is to manipulate the body’s immune system to identify and destroy these cancer cells throughout the body. The Ad/PSA vaccine was developed by inserting the PSA gene into bacteria and viruses and using immune-stimulatory deoxyribonucleic acid (DNA) to modulate the body’s anti-tumor response. Enabling a patient’s immune system to produce anti-antigens and attack cancer cells can improve quality of life and extend survival. Earlier studies in mice demonstrated the vaccine’s efficacy as it produced strong anti-PSA and, as a result, powerful anti-prostate cancer immunity.
This Phase I clinical trial assessed the performance of the Ad/PSA vaccine in men with measurable metastatic prostate cancer. Patients with D2 or D3 cancers (median age 71, median PSA 128 ng/ml) were treated with one of three dose levels of the vaccine and were followed with physical and clinical chemistry exams at two and three weeks and two, four, eight and 12 months. Median follow up was 12 months and median survival was 18 months.
After receiving the vaccine, at least 40 percent of patients developed immune responses to PSA, with anti-PSA antibodies produced in 42 percent of patients and anti-PSA T-cell responses in 71 percent. 57 percent of patients survived longer than predicted, with doubling time increased in 48 percent. Longest survival was 71 months – nearly six years.
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