Licorice Root Extract and Docetaxel in Treating Patients With Metastatic Prostate Cancer That Did Not Respond to Hormone Therapy

DISEASE CHARACTERISTICS:

* Diagnosis of prostate adenocarcinoma

  * Metastatic disease
* Must have failed initial hormonal therapy and have disease progression after at least one chemotherapy regimen\*, meeting any of the following criteria:

  * Progressive PSA ≥ 5 ng/mL, as evidenced by 2 separate measurements taken ≥ 2 weeks apart with the second PSA measurement greater than the first one and PSA measurement at screening greater than the first one
  * Progressive measurable disease (e.g., changes in the size of lymph nodes or parenchymal masses or appearance of new lesions on physical examination or x-ray/CT scan) with a PSA level at screening ≥ 5 ng/mL
  * Progressive bone metastasis (e.g., presence of new lesions on a bone scan) with a PSA level at screening ≥ 5 ng/mL NOTE: \*Prior chemotherapy must include a taxane therapy, but disease progression does not have to follow taxane therapy
* Patients must maintain primary androgen ablation (hormonal) therapy AND experience disease progression while not receiving antiandrogen therapy

PATIENT CHARACTERISTICS:

* ECOG performance status 0-1
* Life expectancy ≥ 6 months
* Absolute neutrophil count ≥ 1,500/mm\^3
* Platelet count ≥ 100,000/mm\^3
* WBC ≥ 3,500/mm\^3
* Bilirubin ≤ 1.2 mg/dL
* Creatinine ≤ 1.5 mg/dL
* SGOT or SGPT ≤ 1.5 times upper limit of normal
* No other prior malignancy unless treated with curative intent and free of disease for the time period considered appropriate for the specific cancer
* No uncontrolled hypertension
* No active infections
* No known HIV positivity
* No uncontrolled medical condition that would preclude study therapy
* No diagnosis of major depression or suicidal ideation
* No problems with oral absorption

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* More than 4 weeks since prior surgery or radiotherapy and recovered
* At least 4 weeks since prior flutamide
* At least 6 weeks since prior bicalutamide
* No prior or concurrent herbal supplements or thiazide diuretics
* No other concurrent investigational or commercial agents or therapies