Localized Prostate Cancer Deaths Remain Low After 20 Years
The death rate in patients with localized prostate cancer remained stable and low after more than 20 years of follow-up, a large retrospective study reported in the May 3 Journal of the American Medical Association (JAMA).
The study is based on a risk analysis of 767 men in the Connecticut Tumor Registry (CTR) diagnosed with prostate cancer between 1971 and 1984 and treated by either observation or delayed androgen withdrawal. "Men with low-grade prostate cancers have a minimal risk of dying from prostate cancer during 20 years of follow-up," note the researchers, who were led by Dr. Peter C. Albertsen of the University of Connecticut Health Center.
The study updates and confirms the authors' initial report published in 1998 on the same patient cohort. "Because these men have been followed continuously by the CTR, we had an opportunity to extend our follow-up to 20 years to determine whether prostate cancer mortality rates declined, remained constant, or increased after 15 years," the researchers explain.
The prostate cancer death rate among the patient cohort was 33 per 1,000 person-years during the first 15 years and 18 per 1,000 person-years after 15 years of follow-up. These rates were not statistically different after adjusting for the more favorable histology profiles among men who survived more than 15 years from diagnosis. "The annual mortality rate from prostate cancer appears to remain stable after 15 years from diagnosis, which does not support aggressive treatment for localized, low-grade prostate cancer," the researchers conclude.
The authors contrasted their findings with a similar, Swedish long-term follow-up study published in JAMA on June 9, 2004. That study of 223 men with localized prostate cancer diagnosed between 1977 and 1984 found an unexpected and substantial three-fold increase in mortality rates from prostate cancer among men who were alive 15 years after diagnosis.
One factor that may contribute to this difference, the researchers suggest, is that the Swedish study classified prostate tumors using the World Health Organization grading system. Patients in the Connecticut study were classified using Gleason scores. The two grading systems "are based on fundamentally different criteria and may result in different classifications, especially among men with moderately differentiated disease," say the researchers.
Among the Connecticut patients with low Gleason scores (2-4), there were 6 deaths per 1,000 person-years, after a median observation period of 24 years. In contrast, those with high Gleason scores (8-10) had a "high probability of dying from prostate cancer within 10 years of diagnosis," - 121 deaths per 1,000 person years, the researchers report.
Dr. Howard L. Parnes, chief of NCI's Prostate and Urologic Cancer Research Group, concurred with Dr. Gann that the patient cohort in the Connecticut study is very different from many patients seen today after the advent of widespread prostate-specific antigen (PSA) testing in the 1990s. Most of the Connecticut patients were found to have prostate cancer based upon transurethral resection of the prostate, Dr. Parnes noted. "On the other hand," he said, "in the PSA era, high-grade disease is likely to have a better prognosis than previously, because we are now more likely to find high-grade disease when it is smaller volume and confined to the prostate than we did in the pre-PSA era."
By Bill Robinson