A connection between bone mineral content and high-risk prostate cancer?
Posted Jul 30 2010 12:00am
New data published in the July issue of the British Journal of Urology International suggest the possibility of a connection between a man’s bone mineral density and his risk for prostate cancer, most particularly the more aggressive and dangerous forms of the disease.
Loeb et al. hypothesized that because advanced forms of prostate cancer tend to show up most commonly as metastases in the bones there might be some form of connection between bone physiology and the progression of prostate cancer over time. As an initial way to test this idea, they decided to see if there were any differences between the bone mineral content (BMC) of men who developed life-threatening types of prostate cancer and men with prostate cancer but no indication of metastasis. To do this, they went back to look at data collected as part of the Baltimore Longitudinary Study of Aging a study that has been tracking health-related data for more than 50 years for hundreds of people in the Baltimore area.
Specifically, Loeb and her collegues were able to identify 519 men whose bone mineral content was measured between 1973 and 1984 as part of the aging study. They then looked for any association between the serial BMC data and the development of overall and high-risk prostate cancer over the next 30 years. For all prostate cancer cases, BMC was censored at the time of diagnosis.
The core results of their study showed the following:
Median overall follow-up was 21.1 years (range, 0.2–35.0 years) after the last BMC measurement.
76/519 men (14.6 percent) were later diagnosed with prostate cancer (18 with high-risk and 58 with low- or intermediate-risk disease).
BMC decreased more with age in the healthy (control) men than among men diagnosed with prostate cancer (P = 0.018).
BMC tended to decline less with age in men with high-risk prostate cancer thqan in men were were not high-risk cases.
The authors conclude that, in this study population, there was a statistically significant difference in the distribution of BMC men who did and men who did not develop prostate cancer, over an extended follow-up. Furthermore, they note that, ”BMC appeared to decline to a greater extent with age among healthy controls than in men with prostate cancer, especially high-risk disease.”
However, as noted in a media release from Johns Hopkins Medicine about this study, Loeb et al. do not believe that bone density scans can be used as a method to test for risk of prostate cancer. This study was both retrospective in natuire and too small to produce generalizable resulst. The researcher’s initial goal was only “to better understand the link between prostate cancer and bone.” The key learning from this study at this time is only that the same factors that influence bone density (e.g., level of sex hormones or growth factors in bone may also be stimulating prostate cancer to develop and metastasize.
An additional fact provided in the media release, however, is that the study results remained valid even after the researchers accounted for lifestyle factors that might influence bone density, such as smoking, body mass index, and intake of dietary calcium and vitamin D.