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March 10, 2009 |
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The March, 2009 issue of Nutrition and Cancer published the finding of Seattle's Fred Hutchinson Cancer Research Center of an association between long term consumption of zinc supplements and a reduced risk of advanced prostate cancer in men.
Prostate tissue contains ten times the level of zinc than other soft tissues in the body, while adenocarcinoma cells from prostate tumors lose the ability to concentrate the mineral. These and other factors led Emily White and colleagues to hypothesize that prostate cancer risk could be lowered by increased zinc intake. For the current study, they evaluated data from 35,242 men between the ages of 50 to 76 who participated in the VITamins and Lifestyle (VITAL) study of the impact of dietary supplements on cancer risk. Questionnaires completed upon enrollment provided information concerning diet and nutritional supplement intake over the past ten years, as well as demographic characteristics and health history. Eight hundred thirty-two of these participants developed invasive prostate cancers over a four year follow-up period, categorized as local, regional or distant invasion.
Zinc from diet or diet plus supplements was not found to be associated with prostate cancer risk. While a weak relationship was observed between a reduced risk of all invasive prostate cancers and long term supplementation with more than 15 milligrams zinc per day, the risk of advanced prostate cancer was significantly lower among subjects who reported supplementing with this amount of zinc.
In their discussion of the findings, the authors note their observation of a greater reduction in the risk of prostate cancer associated with zinc among those in this study whose vegetable intake was high, which suggests that supplementing with zinc could be of benefit to those whose absorption of the mineral is impaired due to increased phytate intake from plant foods.
"If future studies support these results, it may suggest that zinc supplements may be beneficial for some subgroups of men for the most adverse forms of the disease," the authors conclude. |
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Not all prostate cancer (PC) is systemic, any more than all breast cancer or other tumor types are systemic. If they were, we would never cure PC, breast cancer, or any other malignancy. Physicians claiming that every man with PC needs androgen deprivation therapy (ADT) as primary and sole therapy are blindly ignoring the growing numbers of men who present 8 to 15 years after radical prostatectomy (RP) or radiation therapy (RT) with a flat prostate specific antigen (PSA) graph. Emphasis on the use of routine PSA monitoring starting annually at the age of 40 with PSA velocity and doubling time determinations as a standard part of PSA reporting will increase the numbers of men diagnosed earlier, with a lower tumor burden, and cured with local modalities of treatment (Labrie et al, J. Clin. Endocrinol. Metab, 1995; Labrie et al. Urology, 1996). PSA testing with these enhancements should start earlier, at age 35, in men with a familial history of PC.
In addition, the use of routine free/total PSA levels should increase our ability to diagnose PC earlier since fractionation of PSA allows us to monitor the malignant-associated portion of PSA called complexed PSA. Evaluation of risk of PC using neural net technology as per the ProstaSure blood test also will enable an earlier diagnosis of PC (Babaian et al., Urology, 1998). As our standard and hopefully routine approach to monitoring PSA and other biological expressions of tumor cell activity increases, the percentage of men cured of PC should increase as well.
This is borne out in a recent report in which PC was detected in 22% (73/332) of men 50 years or older whose PSA reading was between 2.6 and 4. All cancers detected in this setting were clinically localized. This study indicates that PSA readings greater than 2.6 and less than 4.0 may represent a 22% risk of PC (Catalona et al., JAMA, 1997). The use of a free PSA test would help determine which of these men whose PSA readings were greater than 2.6 but less than 4.0 have a high probability of PC versus a low probability of PC. Such a test could reduce the number of unnecessary biopsies in the low-risk subset and focus a need for more comprehensive biopsying in the high-risk subset. |
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