Measuring Our Progress on Prostate Cancer
Prostate cancer is an ideal example of the successes, challenges, and setbacks we have experienced in our efforts to eradicate cancer. Prostate cancer remains the most common cancer overall and the second leading cause of cancer-related death in men. And, unfortunately, African American men continue to be disproportionately affected by prostate cancer to a significant degree.
Nevertheless, it's estimated that there are approximately 1.7 million prostate cancer survivors in the United States today and prostate cancer mortality has decreased by 4 percent per year since 1994 - evidence that we are indeed making progress against this particular foe.
Last week, I spoke at the annual meeting of the Canadian Urological Association and talked with attendees about the headway that has been made on prostate cancer, including some of the findings from the Prostate Cancer Progress Report, recently posted on cancer.gov at http://prg.cancer.gov/prostate/progress.pdf. The report provides a comprehensive overview of NCI's efforts from to 2002 in response to the Progress Review Group (PRG) recommendations on prostate cancer issued in 1998 - the first-ever NCI PRG report.
During those 5 years, NCI tripled funding for prostate cancer research, from $86.9 million to $278.4 million, nearly doubled the number of projects relevant to prostate cancer, more than doubled the relevant individual training and career development awards, and expanded the prostate Specialized Programs of Research Excellence network from 3 to 11 sites.
As the Progress Report documents, we now better understand this disease and how to prevent and treat it. NCI-supported research published in 2001 and 2002, for example, has shown that the protein TGF-beta plays an important role in initiating and promoting angiogenesis and prostate tumor growth. In one experimental model, use of a TGF-beta inhibitor resulted in prostate tumors that had fewer blood vessels and were half the size of tumors in the control group. Meanwhile, because of survival improvements seen in an NCI-sponsored clinical trial, early initiation of hormonal therapy is now the standard of care in node-positive prostate cancer patients. And in the area of prevention, the NCI-sponsored Prostate Cancer Prevention Trial (PCPT), published in 2003, found that the drug finasteride reduced prostate cancer incidence by 25 percent. The study provided a cautionary note, however, as finasteride use also was associated with higher grade tumors.
NCI researchers are continuing to mine blood and tissue samples and data collected during PCPT. As reported last month in the NCI Cancer Bulletin, in a study published in the New England Journal of Medicine, NCI researchers analyzed biopsy samples from almost 3,000 men in the PCPT placebo arm and found that up to 15 percent of men with prostate-specific antigen (PSA) levels below 4 nanograms/milliliter and normal digital rectal exams have prostate cancer and that 15 percent of these cancers are high-grade.
These data highlight the need to develop prognostic markers beyond PSA and tumor grade to identify men most likely to benefit from treatment. And NCI is doing just that. The NCI Early Detection Research Network, for example, is working toward developing and validating genomic and proteomic technologies to identify biomarkers of prostate cancer prognosis. In addition, NCI researchers are conducting molecular epidemiological studies using samples collected during PCPT to identify men with genetic polymorphisms that make them most likely to benefit from prevention strategies that use finasteride.
Then there are trials like the NCI-funded SELECT, a study that has completed enrollment (with approximately 35,000 participants thus far) and should provide important information on whether the dietary supplements selenium and vitamin E can prevent prostate cancer.
There are, of course, critical gaps in our understanding of prostate cancer. But in many ways, this malignancy is representative of our overall effort against cancer. Progress has been incremental, and new insights often beget new questions. But there is a consistent flow of fresh ideas and intriguing findings that spurs us forward, driving the research engine that translates discoveries into real advances for patients.
Dr. Andrew C. von Eschenbach