Paricalcitol in Treating Patients With Advanced Prostate Cancer and Bone Metastases

Phase II Trial of Zemplar (19-nor-1 a,25-Dihydroxyvitamin D2, Paricalcitol Capsule) on Bony Remodeling in Advanced Androgen-Insensitive Prostate Cancer

RATIONALE: Paricalcitol may help prostate cancer cells become more like normal cells, and to grow and spread more slowly. It may also stop the growth of tumor cells in bone.

PURPOSE: This phase II trial is studying how well paricalcitol works in treating patients with advanced prostate cancer and bone metastases.

OBJECTIVES:

Primary

• To explore the relationship between paricalcitol therapy and markers of bone formation in patients with androgen-refractory, advanced prostate cancer with bone metastases.

Secondary

• To explore the relationship between paricalcitol therapy and markers of bone resorption in these patients.

OUTLINE: Patients receive oral paricalcitol once daily for 10 weeks in the absence of unacceptable toxicity.

Patients undergo blood sample collection periodically to determine markers of bone formation and resorption by ELISA; parathyroid hormone (PTH) levels by immunometric assay; prostate-specific antigen (PSA) levels by immunoassay; and 25-hydroxyvitamin D and 1,25(OH)_2D levels by radioimmunoassay.

Patients also undergo a bone densitometry (DEXA scan) at baseline and at 10 weeks to assess changes in bone strength.

Quality of life is assessed prior to, during, and after completion of treatment. Questionnaires include the Pain Inventory, the Brief Pain Inventory, the Functional Assessment of Cancer Therapy-G (FACT-G), and the Analgesic Use Diary (Narcotic Pain Medication Logbook).

After completion of study treatment, patients are followed every 6 months for 1 year.

Inclusion:

• Histologically or cytologically confirmed advanced adenocarcinoma of the prostate

  - Radiographically proven bone metastasis from prostate cancer

• Androgen refractory disease (including anti-androgen withdrawal)

• Secondary hyperparathyroidism, defined as two parathyroid hormone (PTH) values > 70 pg/mL, 14 days apart

• ECOG performance status 0-2

• Leukocytes ≥ 3,000/μL

• Absolute neutrophil count ≥ 1,500/μL

• Platelets ≥ 100,000/μL

• Total bilirubin normal

• AST/ALT ≤ 2.5 times upper limit of normal

• Creatinine clearance ≥ 60 mL/min

• Calcium normal

• 25-hydroxyvitamin D (25-OHD) ≥ 20 ng/mL

• 1,25(OH)_2D normal

• Patients with serum 25-OHD indicative of vitamin D insufficiency are eligible provided they are treated with ergocalciferol to raise 25-OHD levels to 20 ng/mL prior to paricalcitol therapy

• More than 8 weeks since prior bisphosphonates

• More than 2 weeks since prior palliative radiotherapy

• More than 4 weeks since other prior therapy

• No more than one prior taxane-containing chemotherapy regimen for metastatic disease

• Multiple lines of prior therapy with hormonal agents allowed

• Concurrent corticosteroids allowed provided the dose remains stable during the study period

Exclusion:

• Underlying metabolic bone disease or vitamin D deficiency
• History of hypercalcemia
• Concurrent uncontrolled illness or co-morbid condition (including psychiatric illness) that would interfere with study compliance
• Concurrent ergocalciferol supplementation
• Concurrent chemotherapy or hormonal therapy
• Concurrent investigational or commercial agents for the malignancy