Objectives. To determine the hormonal (luteinizing hormone [LH] and testosterone) and biochemical (serum prostate-specific antigen [PSA]) response to withdrawal of luteinizing hormone-releasing hormone (LHRH) agonists in patients who received more than 2 years of LHRH therapy for advanced prostate cancer. Methods. Fourteen patients with clinical Stage T3 or higher prostate cancer and no evidence of clinical or biochemical progression, who had received 2 years or more of LHRH therapy, were enrolled at the time of their scheduled 3-month depot injection. Patients underwent history, physical examination, and measurement of serum PSA, LH, and testosterone at baseline, monthly for 3 months, and then every 3 months for 1 year following LHRH withdrawal. Results. The mean age of patients was 70.3 years (range 56 to 84). Patients previously received LHRH agonist for a mean of 38.6 months (range 25 to 82). All patients had castrate levels of testosterone (median 10.0 ng/dL) and suppressed LH levels (median 0.1 mIU/mL) at baseline. Median baseline PSA was 0.15 ng/mL. On multiple groupwise comparison, there was no significant change (compared with baseline) in LH or testosterone until 6 months after withdrawal and no change in PSA throughout the duration of the study (median PSA at 12 months 0.30 ng/mL). Despite significant increases in LH and testosterone when compared with baseline beginning at 6 months, both LH and testosterone remained markedly suppressed, with median testosterone remaining in the castrate range at both 6 and 9 months and significantly below the lower limit of normal at 12 months (median 111.0 ng/dL). Despite no statistically significant change for the entire cohort in serum PSA, a rising PSA was noted in 4 patients between 3 and 9 months, and LHRH therapy was reinitiated. The remaining patients continued to have suppressed LH and testosterone, with 4 patients remaining in the castrate range at 12 months. Conclusions. The recovery of function of the hypothalamic-pituitary-testicular axis after prolonged LHRH administration is variable. Castrate levels of testosterone and suppressed LH may persist even up to 1 year after discontinuing LHRH. These results have significant implications regarding the interpretation of clinical trials incorporating neoadjuvant and adjuvant hormonal therapy. Further studies are needed to expand on these preliminary observations and should also address the feasibility of incorporating LHRH withdrawal into clinical practice.
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