Prostate Cancer, Support Groups  and Prostate Cancer Treatment

In Scandinavia and a number of other areas in Europe, watchful waiting had been used for low-grade prostate cancer patients who have early stage disease. This is no longer true.  Watch Waiting in Europe is now on par with the United States.  Watchful waiting, or observation-deferred treatment, is a strategy in which a patient is monitored periodically but receives no treatment. Generally this strategy is advised for older men with limited life expectancy, those with localized prostate cancer who do not want to experience the side effects of conventional treatment, and those who have cancers that are not likely to kill them. Although there are certainly arguments in this country regarding observation, the disease specific survival figures do support a place for observation depending upon the stage, grade, and age of the patient.

The question of whether to watchful wait or treat prostate cancer will continue to be asked until there are definitive answers from clinical trials, such as the Prostate Cancer Intervention Versus Observation Trial (PIVOT study). This multi-institutional cooperative study involves comparing early or clinical localized prostate cancer patients who undergo radical prostatectomy or watchful waiting alone (by a randomization process). This study will monitor and report patients in terms of progression-free survival, freedom from metastatic disease, disease-specific survival, and overall survival, as well as quality of life. The results will not be evident until approximately 2008, but 5 years into the study, no survival advantage has been noted in either arm.

With the advent of gene therapy, scientists and researchers now believe it should be possible to create prostate-targeted vaccines that would cause an immune response to search for, locate, and destroy prostate cancer.

Provenge, also known as APC8015, is a prostate cancer vaccine currently in phase III clinical trials sponsored by the Dendreon Corporation. The first one of these phase III trials recently reported results. APC or antigen presenting cells are involved in the initiation and expansion of cellular immune responses to carrier and virus-infected cells. Dendritic cells, the most potent APCs, are trained to detect cancer cells by exposure to the target (Valone et al., 2001). Dendritic cells potentiate the effectiveness of the initiation of T-cell and B-cell (lymphocytes) mediated immune responses. Provenge activates these cells to mount a more effective immune response against prostate cancer.

APCs do not kill cancer cells; rather, they alert effector cells, like T-cells, to the presence of cancer. T-cells are the immune system's attack cells, and thus they attack and destroy the cancer cells. Provenge consists of autologous dendritic cells loaded with PA2024, a fusion protein consisting of human prostatic acid phosphatase (PAP) coupled to a targeting molecule, granulocyte-macrophage colony-stimulating factor (GM-CSF). PAP is a tissue-specific antigen that is expressed only by normal prostate cells and is in greater than 90 percent of cancer cells of the prostate. GM-CSF is a cytokine, which regulates the survival, proliferation, and differentiation of granulocyte (white blood cells) and macrophage progenitors (cells that destroy other cells by "eating" them) and which are a potent stimulator of dendritic cells (Rini and Small, 2001).