Purpose: For many years it was believed that higher total testosterone contributed to prostate cancer and caused rapid cancer growth. International guidelines consider that adequate data are not available to determine whether there is additional risk of prostate cancer from testosterone replacement. Numerous studies with multiple designs and contradictory conclusions have investigated the relationship between total testosterone and prostate cancer development. To establish current knowledge in this field we reviewed the literature on total testosterone and the subsequent risk of prostate cancer as well as the safety of exogenous testosterone administration in patients with a history of prostate cancer. Materials and Methods: We searched the literature to identify articles from 1994 to 2014 related to the relationship between total testosterone and prostate cancer. Emphasis was given to prospective studies, series with observational data and randomized, controlled trials. Case reports were excluded. Articles on testosterone replacement safety were selected by patient population (under active surveillance or with a prostate cancer history). We organized our results according to the relationship between total testosterone and prostate cancer, including 1) the possible link between low total testosterone and prostate cancer, 2) the effect of high levels and 3) the absence of any link. Finally, we summarized studies of the risk of exogenous testosterone administration in patients already diagnosed with prostate cancer, treated or on active surveillance. Results: We selected 45 articles of the relationship between total testosterone and prostate cancer, of which 18 and 17 showed a relationship to low and high total testosterone, respectively, and 10 showed no relation. Total testosterone was defined according to the definition in each article. Contradictory findings have been reported, largely due to the disparate methodologies used in many studies. Most studies did not adhere to professional society guidelines on total testosterone measurements. One of 18 series of low total testosterone and prostate cancer adhered to published guidelines while none of 17 showing a relationship of high total testosterone to prostate cancer and only 1 of 10 that identified no relationship between total testosterone and prostate cancer adhered to measurements recommended in the guidelines. In 11 studies the risk of exogenous testosterone was examined in patients with a prostate cancer history. Many studies were limited by small cohort size and brief followup. However, overall this literature suggests that the risk of exogenous testosterone replacement in patients with prostate cancer appears to be small. Conclusions: The relationship between total testosterone and prostate cancer has been an area of interest among physicians for decades. Conflicting results have been reported on the relationship between total testosterone and subsequent prostate cancer. Much of this controversy appears to be based on conflicting study designs, definitions and methodologies. To date no prospective study with sufficient power has been published to unequivocally resolve the issue. The preponderance of studies of the safety of exogenous testosterone in men with a prostate cancer history suggests that there is little if any risk. However, because the risk has not proved to be zero, the most prudent course is to follow such men with regular prostate specific antigen measurements and digital rectal examinations.
