DISEASE CHARACTERISTICS:

• Histologically confirmed prostate cancer

  • Stage D0 (stage IV) disease (i.e., tumor limited to the prostate with rising prostate-specific antigen [PSA] value after definitive local therapy)
  • No metastases (confirmed by bone scan and CT scan of abdomen/pelvis)

• Must have undergone local treatment via prostatectomy or radiotherapy and have shown PSA progression

  • After surgery, PSA values > 0.2 ng/mL, determined by two measurements at least 1 month apart and at least 6 months after prostatectomy
  • After radiotherapy, PSA values ≥ 2.0 ng/mL greater than the nadir achieved after radiotherapy, determined by two measurements at 1 month apart and at least 6 months after the radiotherapy
  • The first two PSA values, along with a third (study baseline) value must all be rising (i.e., there must be an overall rising trajectory, such that the third value cannot be lower than the first value)

PATIENT CHARACTERISTICS:

• ECOG performance status 0-2
• Life expectancy ≥ 6 months
• WBC > 3,500/mm³
• ANC > 1,500/mm³
• Hemoglobin > 10 g/dL
• Platelet count > 100,000/mm³
• Serum creatinine < 1.5 mg/dL OR creatinine clearance > 50 mL/min
• Total bilirubin normal
• ALT and AST < 2.5 times upper limit of normal
• No evidence of retinopathy by ophthalmic exam within the past 12 months
• No serious concurrent systemic disorder that would compromise the safety of the patient or compromise the patient's ability to complete the study, at the discretion of the investigator
• No psoriasis
• No active clinically significant infection requiring antibiotics
• No glucose-6-phosphate dehydrogenase (G6PD) deficiency
• No retinal or visual field changes from prior 4-aminoquinoline compound
• No history of hypersensitivity to 4-aminoquinoline compound
• No other malignancy within the past 5 years except in situ carcinoma (e.g., adequately treated nonmelanoma skin cancer)

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 3 months since prior hormone-ablative treatment (neoadjuvant therapy allowed)
• No concurrent treatment for rheumatoid arthritis or systemic lupus erythematosus
• No concurrent disease-modifying anti-rheumatic drug
• No other concurrent commercially available medications that may either stimulate or inhibit autophagy (e.g., calcitriol and hydroxychloroquine)
• No concurrent medications that may lead to interactions with hydroxychloroquine, including penicillamine, telbivudine, botulinum toxin, digoxin, and propafenone
• No other concurrent hydroxychloroquine for treatment or prophylaxis of malaria
• No other concurrent chemotherapy, immunotherapy, hormonal cancer therapy, radiotherapy, surgery for cancer, or other experimental medications