INTRODUCTION
  78-year-old man with a history of mild kidney failure and a T.I.A., was diagnosed with metastatic prostate cancer with osteoblastic bone lesions. 
The biopsy revealed adenocarcinoma Gleason 7 (4+3). He received lhrh with bicalutamide for almost a year and a half, but his disease progressed. 
In May 2018 the PSA reached >200 while the CT’s and bone scans showed progression of bone metastasis. He started enzalutamide 160 mg daily and his blood exams improved remarkably from the first month. Unfortunately, the patient had known kidney failure and in the first six months his creatinine levels worsened. His ultrasound of bladder and kidneys did not show any abnormal findings of hydronephrosis.
For mild to moderate creatinine failure no dose adjustment is needed. But to severe CrCl <30, no data are available. 
After a short period of interruption of enzalutamide his creatinine levels improved, and the patient started receiving lower levels of enzalutamide. His creatinine levels remained stable, but at some point, the patient started receiving 40 mg per day without informing us. When he finally admitted the real dose the PSA was still normal, and while we tried to persuade him to increase the dose he refused, due to the fear of kidney failure. The last months the patient continues the same dose since the PSA value, remains extremely low. Last PSA value 0.108.
CONCLUSION
This is a case of a patient that despite the suggestions  of his doctors, he lowered the dose of enzalutamide due to the fear of kidney failure and there seems to be a benefit

A man with castrate resistant prostate cancer receiving a smaller dose of enzalutamide than usual,