Prostate Cancer (cont.)
Prostate Cancer Causes
The specific cause of prostate cancer remains unknown. Hormonal, genetic, environmental, and dietary factors are thought to play roles. Yet, the only well-established risk factors for prostate cancer are age, ethnicity, and heredity.
- Age: There is a strong correlation between increasing age and developing prostate cancer. The incidence of prostate cancer increases steadily from less than 1 in 100,000 for men 40 years of age to 1,146 per 100,000 in men 85 years of age. The median age at diagnosis of prostate cancer is 70.5 years of age. More than 80% of prostate cancers are diagnosed in men older than 65 years of age. Autopsy records indicate that 70% of men older than 90 years of age have at least one region of cancer in their prostate.
- Ethnic origin: In the U.S., African American men are 1.6 times more likely than Caucasian men to develop prostate cancer. They are also 2.4 times more likely to die from their disease as compared to Caucasian men of a similar age. Asian Americans, on the other hand, have a much lower chance of getting prostate cancer as compared to Caucasians or African Americans. Internationally, Caucasian men from Scandinavian countries experience the highest rates whereas men from Asia the lowest. Although, these ethnic criteria have been used to study and describe the disease in the past, there is no defined biologic basis for this classification. In other words, these differences in diagnosis and death rates are more likely to reflect a difference in factors like environmental exposure, diet, lifestyle, and health-seeking behavior rather than racial susceptibility to prostate cancer. Recent evidence, however, suggests that this disparity is progressively decreasing with high chances of complete cure in men undergoing treatment for organ-confined prostate cancer (cancer that is limited to within the prostate without spread outside the confines of the prostate gland) irrespective of race.
- Family history: Men who have a history of prostate cancer in their family, especially if it is a first-degree relative such as a father or brother, are at an increased risk of developing prostate cancer. If one first-degree relative has prostate cancer, the risk is at least doubled. If two or more first-degree relatives are affected, the risk increases by 5- to 11-fold.
- Diet: Dietary factors may influence the risk of developing prostate cancer. Specifically, total energy intake (as reflected by body mass index) and dietary fat have been incriminated. In addition, there is some evidence that suggests that obesity leads to an increased risk of having a more aggressive, larger prostate cancer, which results in a poorer outcome after treatment. Nevertheless, the question remains whether there is enough evidence to recommend lifestyle changes specifically to prevent prostate cancer independently of the known health and cardiovascular benefits.
- Infection: Recent evidence has suggested the role of sexually transmitted infections as one of the causative factors for prostate cancer. People who have had sexually transmitted infections are reported as having 1.4 times greater chance of developing the disease compared to the general population.
- Cadmium: Exposure to chemicals such as cadmium may be implicated in the development of prostate cancer.
- Selenium and vitamin E: While initial reports of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) found no reduction in risk of prostate cancer with either selenium or vitamin E supplements, recent conclusions confirmed that vitamin E not only fails to prevent prostate cancer but actually increases prostate cancer risk. In this study, men who took vitamin E supplement 400 IU per day had a 17% increase in their risk of the disease. Therefore, patients should be advised not to take vitamin E supplement.
- Vitamin C: Vitamin C 500 mg PO every other day did not reduce the incidence of prostate cancer in the Physicians' Health Study-II (PHS II) after a median follow up of 8 years. Therefore vitamin C should not be recommended to prevent prostate cancer.
Factors not associated with prostate cancer:
- Benign prostatic hyperplasia (BPH): Prostate cancer does not appear to be related to benign prostatic hypertrophy (BPH); however, BPH increases the risk of a high PSA, which may lead incidentally to a diagnosis of disease.
- Vasectomy: Vasectomy is not a risk factor for prostate cancer.
- Sexual activity: There is no proven link between frequency of sexual activity and prostate cancer risk.
Pierre-Alain Hueber, MD, PhD
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