Introduction: Abiraterone acetate (plus prednisone) and enzalutamide are both approved therapies for men with metastatic castration-resistant prostate cancer (mCRPC), with similar improvement in progression-free survival and overall survival, in docetaxel pretreated as well as chemotherapy-naïve patients. Although phase 3 trial evidence is lacking, these agents seem to have similar efficacy but different toxicity profile.
Patient Information: We report the case of a 56yo man with no relevant past medical history, who presented with acute urinary retention in Nov2009. A prostatic biopsy documented prostatic adenocarcinoma (ADC), Gleason 8 (3+5). Staging exams excluded the presence of metastasis. The patient refused radical prostatectomy and was lost to follow-up. In Dec2015, the patient presented to the emergency department with a 2-month history of pain on the lower back, shoulders and pelvis, anorexia and weight loss, as well as nocturnal enuresis since 2014. A lumbar spine CT scan and a bone scintigraphy showed diffuse bone metastases; PSA was 20.4 ng/mL.
Treatment: Gonadotropin-releasing hormone analogue leuprorelin was started in Jan2016 and docetaxel chemotherapy (according to CHAARTED and STAMPEDE trials) was added between April and July 2016, with optimal tolerance and clinical, biochemical and radiological improvement. PSA nadir was 0.10 ng/mL (Oct2016) with slow increase until Jul2018 the PSA, with no response to the addition of bicalutamide, but no clinical or radiological evidence of progression. In Aug2018, the patient reported increase in the pelvic and lumbar pain, had a PSA of 6.08 ng/mL) and enzalutamide 160 mg qd and zoledronic acid were started. After 2 months, patient reported fatigue and drowsiness with impact on quality of life which did not improve with dose reduction to 120 mg qd, despite the improvement in pain and PSA decline to 0.21 ng/mL. Anti-androgen therapy was switched to abiraterone acetate and prednisolone in Nov2018, with resolution of side effects.
Follow-Up: The patient remains on abiraterone acetate until today, with good tolerance, clinical benefit, sustained PSA response (0.10 ng/mL in Aug2019) and radiologic control of the disease. This case illustrates how treatment of cancer is a thin line between maximization of efficacy and avoidance of toxicity.
