1. The primary objective of this study is to assess the feasibility of treating patients with metastatic castration resistant prostate cancer with mitotane. Secondary objectives are to assess safety and tolerability as well as response rate of therapy
2. To assess the toxicity of Mitotane in men with HRPC
3. To assess the relationship between baseline serum adrenal androgens and their response to Mitotane

All patients will undergo pre-study assessment for symptoms, performance status, ECG, CT abdomen/pelvis, Bone scan, Complete blood count tests(hematology) , Biochemistry tests like serum electrolytes, liver function tests, coagulation profile, testosterone and PSA tests.

Mitotane will be administered 1.5g daily escalation to maximum of 5 g daily then adjusted according to serum levels and tolerability

Physical examinations, hematology, biochemistry tests, and toxicity evaluations will be measured throughout patients on protocol treatment

Mitotane serum level will be analyzed every second cycle

Research bloods include; ACTH, cortisol, deoxycorticosterone, aldosterone, corticosterone, and testosterone, androstenedione, dehydroepiandrostenedione (DHEA), DHEA sulfate (DHEA-S) and estradiol will be collected only in cycle 1,3 and 5

Inclusion Criteria:

• Biopsy-proven prostate cancer OR a clinical picture consistent with metastatic prostate cancer with high levels of serum PSA (>20ng/ml)

• Progressed on docetaxel chemotherapy after a minimum of 3 cycles and/or stopped treatment because of toxicity. Patients may have had previous mitoxantrone, either before or after docetaxel treatment

• Response to a minimum of a 50% fall in PSA maintained for 4 weeks and then progressed through abiraterone treatment

• At least 2 consecutive rising PSAs measured at least 1 week apart . Patients must have ceased abiraterone at least 1 week prior.

• Serum PSA > 10 ng/ml

• ECOG performance status </= 1 (Karnofsky >/=60%)

• Normal organ and marrow function as defined:

  • Absolute neutrophils count ≥ 1,500/uL
  • platelets ≥100,000/uL
  • total bilirubin ≤1.5 X institutional ULN
  • AST(SGOT)/ALT(SGPT) ≤ 2 X institutional ULN
  • creatinine ≤ 1.5 X institutional ULN

• Men must agree to use adequate contraception prior to study entry

• Life expectancy > 3 months

• CRPC documented by PSA increase despite having: a) orchidectomy OR b) continuous LHRH agonist treatment. This should be documented by a baseline serum testosterone suppression (<1.75 nmol/L)

Exclusion Criteria:

• Prior anticancer treatment with Mitotane
• May not be receiving any other investigational or anticancer agents while on study
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure or evidence of cardiac dysfunction, unstable angina pectoris, cardiac arrhythmia, active peptic ulcer disease, poorly controlled diabetes mellitus, clinically significant or untreated ophthalmologic (e.g. Sjogrens etc.) or gastrointestinal conditions (e.g. Crohns disease, ulcerative colitis) or psychiatric illness/social situations that would limit compliance with study requirements
• Active malignancy at any other site excluding squamous cell or basal cell carcinomas of the skin
• Radiotherapy within the past 4 weeks
• Pre-existing pituitary or adrenal dysfunction
• Patients on spironolactone as this may interfere with the action of mitotane
• Patients on warfarin as mitotane may unpredictably interfere with INR measurements