In a study reported in the journal Cancer, obese men with a BMI of 35 or higher were somewhat less likely to be diagnosed with prostate cancer than were normal-weight men (BMI of less than 25). But if prostate cancer developed in these men, it was more likely to be fatal. During the five years of the study, men with a BMI of 35 or higher were twice as likely to die of their prostate cancer as were normal-weight men.
Results of another study reported in Cancer showed that obese men (BMI greater than 30) who had prostate cancer confined to the prostate or to areas surrounding it were three times more likely to develop metastatic cancer than were normal-weight men with a similar diagnosis. In this 10-year study, being obese more than doubled the risk of dying of prostate cancer.
Factors Affecting Outcome. Prostate cancer specialists suggest several possible explanations for the worse prognosis of obese men. For example, being obese alters estrogen and testosterone levels and increases insulin-related substances that spur the growth of cancer such as insulin-like growth factor-1 (IGF-1).
Another possibility is that men who are obese may be less health conscious and visit their physicians less often than they should, resulting in fewer prostate-specific antigen (PSA) tests and a delayed diagnosis. Obese men also tend to have lower PSA concentrations, possibly because the PSA is diluted in a larger volume of blood. These lower levels delay diagnosis as well.
Last, but not least, excess weight also makes it more difficult for a physician to examine the prostate via a digital rectal exam or biopsy and for a surgeon to perform a successful radical prostatectomy.
