Lenalidomide and GM-CSF in Treating Patients With Prostate Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed adenocarcinoma of the prostate * Androgen-independent disease * Testosterone ≤ 50 ng/mL * Is currently receiving luteinizing hormone-releasing hormone agonists as maintenance or has undergone prior orchiectomy for testosterone suppression * Progressive disease, as defined by ≥ 1 of the following: * Clinical or radiographic evidence of metastases that have progressed irrespective of PSA changes * Asymptomatic (non-opioid requiring) bone-only metastatic disease with a rising PSA on separate measurements ≥ 1 week apart * No symptomatic bone metastases * Biochemical progression (PSA-only disease), defined as having an absolute PSA value of ≥ 2.0 ng/mL on 3 separate measurements ≥ 2 weeks apart with a PSA doubling time of ≤ 10 months * No evidence of CNS (brain or leptomeningeal) metastases or pleural and/or pericardial effusions PATIENT CHARACTERISTICS: * ECOG performance status of 0-1 * ANC ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Serum creatinine ≤ 2.0 mg/dL * AST \< 3 times normal * Bilirubin \< 1.5 mg/dL * PT and PTT normal * Calcium normal * Fertile patients must use effective contraception during and for ≥ 28 days after completion of study therapy * Agrees to abstain from donating blood, semen, or sperm during and for ≥ 28 days after completion of study therapy * No pre-existing peripheral neuropathy \> grade 1 * No active unresolved infection * No known contraindication to lenalidomide or sargramostim * No other malignancies within the past 5 years, except for curatively treated basal cell or squamous cell carcinoma of the skin or stage Ta transitional cell carcinoma of the bladder PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior chemotherapy for metastatic prostate cancer * More than 1 year since prior adjuvant and/or neoadjuvant therapy * More than 4 weeks since prior flutamide (6 weeks for other antiandrogens) * No prior thalidomide or lenalidomide * At least 4 weeks since prior surgery or external-beam radiotherapy and recovered * At least 6 weeks since prior radiopharmaceutical therapy, including samarium-153 or strontium-89, and recovered * No initiation of bisphosphonate therapy within 1 month before and during study therapy * Patients on stable doses of bisphosphonates who show subsequent tumor progression may continue to receive bisphosphonates * Concurrent daily aspirin for the prevention of thrombotic events required * Patients intolerant to aspirin may receive low-dose warfarin as prophylaxis * No other concurrent investigational agents * No other concurrent anticancer therapy, including radiotherapy or thalidomide