152 and 6 months after treatment. However, the validity of these factors has not been clearly established. A previous report showed that Gleason score, PSA nadir, and PSA lev- el 6 months after hormone treatment are prognostic factors that predict the progression to HRPC [5]. Kwak et al. [10] reported that the nadir PSA level after hormone treatment may be the most accurate prognostic factor. Huang et al. [20] suggested that the PSA nadir and time to PSA nadir are important prognostic factors. The PSA level is a useful marker in the diagnosis of prostate cancer, but there are disagreements about its prognostic importance after hor- mone treatment. Collette et al. [21] reported that PSA alone is not an appropriate marker of long-term ther- apeutic benefit in prostate cancer. Yoon [22] reported that free PSA is not a static factor, but rather a dynamic factor that is influenced by various conditions including hormone treatment. Therefore, free PSA and the f/t PSA ratio can be used to predict the prognosis of patients treated by hor- mone treatment. In this study, the number of patients pro- gressing to HRPC was 10 in group 1 and 14 in group 2 (p=0.003). These findings suggest that the nadir f/t PSA ra- tio can be a prognostic factor. Tanaka et al. [23] reported that whereas the f/t PSA ratio is unaffected by the stage of prostate cancer at the time of diagnosis, it does rise during the period in which the cancer is responsive to hormone treatment and then slowly re- turns to the pretreatment level as the cancer recurs. Recent literature has shown that the difference in the f/t PSA ratio between a group showing early biochemical recurrence and a group continuously responsive to hormone treatment be- comes greater at 8 to 10 months after the initiation of treat- ment compared with the time of diagnosis. Some authors have argued that the pattern of change in the f/t PSA ratio is dependent on the response to treatment. In this study, the f/t PSA ratio of both groups steadily increased until 6 months after the initiation of hormone treatment. Howev- er, the f/t PSA ratio continuously declined since 9 months in group 2, whereas it remained elevated until 9 months and then slowly declined in group 1. The pattern of change in the f/t PSA ratio is thought to be related to the response to hormone treatment, similar to PSA. Such results are consistent with the results of previous studies showing that the f/t PSA ratio is affected not only by hormone treat- ment of advanced prostate cancer but also by the degree of response to hormone treatment. These results also demon- strate the importance of the f/t PSA ratio as a supple- mentary prognostic marker in the hormone treatment of advanced prostate cancer that can be used simultaneously with PSA. CONCLUSIONS When patients were divided into two groups on the basis of the nadir f/t PSA ratio, progression to CRPC was sig- nificantly higher in the group with a lower f/t PSA ratio. In addition, the pattern of change in the f/t PSA ratio was Korean J Urol 2012;53:149-153 Kim et al significantly different after 9 months. Collectively, the f/t PSA ratio can be used as an additional marker for the prog- nosis of hormone treatment. Further additional large-scale studies elucidating the clinical significance of f/t PSA ratio monitoring in the hormone treatment of advanced prostate cancer are necessary. CONFLICTS OF INTEREST The authors have nothing to disclose. REFERENCES 1. American Cancer Society. Cancer facts and figures 2005. Atlanta: American Cancer Society; 2005. 2. Ministry for Heath, Welfare and Family Affairs. Annual report of cancer incidence (2006) and survival (1993-2006) in Korea. Seoul: Ministry for Heath, Welfare and Family Affairs; 2009. 3. 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