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BACKGROUND: A variety of methods for testosterone replacement therapy (TRT) exist and major potential risks of TRT have been well established. Risk of developing polycythemia secondary to exogenous testosterone (T) has been reported to range from 0.4% to 40%. Implantable T pellets have been used since 1972 with benefits of improved treatment compliance, less frequent dosing, as well as avoidance of potential drug transference. Secondary polycythemia has been reported to be as low as 0.4% in studies reviewing testosterone pellet insertion, however our experience has suggested a higher rate.
METHODS: We conducted an IRB approved single institution retrospective chart review (2009-2013) to evaluate whether our rates of secondary polycythemia were higher than previously reported in 231 men treated with subcutaneously implanted testosterone pellets. Serum hematocrit (Hct) levels were analyzed as a function of time from implantation, number of pellets implanted, body mass index (BMI), number of implantations and preimplantation forms of T therapy and T levels. Kaplan-Meyer survival curves were used to estimate two scenarios of “fail”: the time until development of polycythemia (Hct >50%) and time until treatment switch from pellet implantation to another form of TRT.
RESULTS: The mean age of patients was 57 yrs and the mean
BMI was 31.7. 58/251 (25%) of the patients had a Hct >50%. The mean number of pellets administered was 12 (range 6 to 16). The mean follow up was 566 days. The fail time whereby 25% of patients developed polycythemia was 16 months. The rate of development of polycythemia at 12 months was estimated at 18% and 33% at 24 months. Survival curves while on pellet therapy were estimated between those who had transdermals, injectables, combination, or no treatment prior to the study; however, no significant difference was detected. The time whereby 25% of patients switched treatment was 34.5 months. The rate of treatment switch at 12 months was 10% and 22% at 24 months. In addition, a significant difference was detected among the prior testosterone treatment groups (p=0.023). Patients who had a treatment history of injectable testosterone were more likely to switch from pellets to another form of replacement.
CONCLUSIONS: The incidence of erythrocytosis while on T pellet therapy resulting in secondary polycythemia is higher than previously established. Patients who were on T injections prior to pellet therapy are more likely to stop pellet therapy for another option.