Abiraterone With Discontinuation of Gonadotropin-Releasing Hormone Analogues in Metastatic Prostate Cancer

Abiraterone inhibits the CYP17A enzyme, which is a critical enzyme in androgen biosynthesis.
Abiraterone has regulatory approval in metastatic castration-resistant prostate cancer
(mCRPC) in both chemotherapy-naïve and in the post-docetaxel setting based upon results from
two randomized phase III studies. Abiraterone is also proven to extend survival in the
metastatic, hormone-naïve population based on two phase III studies. Abiraterone is a
castrating agent, but, other than a small first in human study, all clinical studies have
been done in conjunction with gonadotropin-releasing hormone (GnRH) analogues. Maintaining
castrate level of serum testosterone is critical in the treatment of metastatic prostate
cancer. It is unknown if GnRH analogues must be continued to maintain castrate levels of
serum testosterone in patients treated with abiraterone.

Inclusion Criteria:

1. The patient must be able to provide study-specific informed consent prior to study
entry

2. Age ≥ 18

3. ECOG Performance Status 0-2

4. Pathologically proven diagnosis of prostate adenocarcinoma

5. Patients must have metastatic prostate cancer

6. Patients may have mCRPC or may have metastatic castration-sensitive disease.

7. Patients must be maintained on a GnRH analogue (agonist (leuprolide, goserelin,
triptorelin, histerelin, deslorin) or antagonist (degarelix))

8. The patient and the investigator have decided that the next line of cancer therapy
will be abiraterone plus prednisone and the initial dose of abiraterone will be 1000
mg daily. Or patients may already be on abiraterone with prednisone at a dose of 1000
mg daily along with a GnRH analogue.

9. Lab values meeting the following criteria

1. Total testosterone level of <50 ng/dl

2. Total bilirubin < 2.0 X Upper Limit of Normal (ULN)

3. Aspartate aminotransferase (AST) ≤ 3 X ULN

4. Alanine aminotransferase (ALT ) ≤ 3 X ULN

5. Absolute Neutrophil Count > 1.5 K/mm3

6. Platelets > 100 K/mm3

7. Hemoglobin ≥9.0 g/dL

8. calculated creatinine clearance ≥ 30 mL/min

Exclusion Criteria:

10. History of bilateral orchiectomy

11. History of hypopituitarism

12. For patient not yet started on abiraterone with prednisone, uncontrolled hypertension
(systolic blood pressure >170 mm Hg or diastolic blood pressure >100 mm Hg)

13. Patients must not have New York Heart Association Class III or IV heart failure at the
time of screening. Patients must not have any unstable angina, myocardial infarction,
or serious uncontrolled cardiac arrhythmia within 6 months prior to registration

14. Any other serious illness or medical condition that the principal investigator feels
would make the patient a poor candidate for this study