Itraconazole as a Noncastrating Treatment for Biochemically Recurrent Prostate Cancer: A Phase 2 Study

Abstract

Background Patients with biochemically recurrent prostate cancer and short prostate‐specific antigen doubling time (PSADT) are at risk for metastasis yet may wish to avoid androgen deprivation therapy. Itraconazole may have antitumor activity without affecting circulating androgen levels. We therefore evaluated itraconazole as a potentially noncastrating treatment approach in biochemically recurrent prostate cancer. Patients and Methods Patients with biochemically recurrent prostate cancer and PSADT ≤ 15 months, with serum testosterone > 150 ng/dL, were prospectively enrolled. The primary end point was the proportion of patients who experienced ≥ 50% decline from baseline in serum prostate‐specific antigen (PSA) by week 12. Results Twenty‐one patients were enrolled. The median (range) age, baseline PSA, and PSADT at study entry was 72 (49‐76) years, 7.6 (1.5‐45.5) ng/mL, and 5.7 (1.2‐13.0) months, respectively. Among 19 patients with evaluable data, 1 patient (5%) had a > 50% PSA decline. Nine patients (47%) experienced any PSA decline (mean decline 25.0%, range 2%‐60%) by week 12. Among 10 patients without a PSA decline, the on‐treatment versus pretreatment PSADT was not significantly longer (median 6.8 vs. 4.3 months, P = .17). There was no significant change from baseline to week 12 in serum testosterone (median change = 32.4%, P = .21) or androstenedione (median change = −8.3%, P = .85). The most common adverse events were edema (52%), fatigue (38%), hypertension (24%), and hypokalemia (24%). Conclusion Itraconazole modulates serum PSA levels without lowering serum testosterone. However, the magnitude of effect is modest, and treatment carries risk of toxicities associated with mineralocorticoid excess. Micro‐Abstract Itraconazole has been previously shown to have antitumor activity independent of its effect on circulating androgen levels and was therefore investigated as a noncastration approach in patients with biochemically recurrent prostate cancer. Results indicate that itraconazole indeed has a modest impact on serum prostate‐specific antigen levels without affecting circulating androgen levels. However, toxicities pertaining to mineralocorticoid excess limits the further development of itraconazole in this patient population.