In summary, in vitro and in vivo studies, as well as early phase clinical trial, have shown a promising role for both calcitriol and NSAIDs in the treatment of prostate cancer. Moreover, calcitriol and NSAIDs both exert their antiproliferative effect by decreasing prostaglandin levels, but they do so by different mechanisms. Thus, there is reason to believe that their combined effects on prostaglandins may be synergistic. Preliminary in vitro assays in which calcitriol is given in combination with one of two different NSAIDs (Naprosyn or sulindac) to LNCaP cell lines have indicated such synergy. This observation provides the rational for using them in combination for the treatment of prostate cancer. In addition, it is hoped that any synergy noted would allow for the use of lower doses of NSAIDs.