DISEASE CHARACTERISTICS:

• Histologically confirmed thyroid cancer

  • One of the following subtypes:

    • Papillary thyroid cancer
    • Follicular thyroid cancer
    • Hürthle cell thyroid cancer
    • Insular thyroid cancer
    • Medullary thyroid cancer
    • Mixed histology thyroid cancer
    • Poorly differentiated thyroid cancer
    • Tall-cell thyroid cancer
  • Metastatic and/or locally advanced or locally recurrent disease

• Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR ≥ 10 mm by spiral CT scan

  • Lesions in a previously irradiated area allowed provided there has been subsequent disease progression of the irradiated lesions

  • The following are not considered measurable disease:

    • Bone lesions
    • Leptomeningeal disease
    • Ascites
    • Pleural or pericardial effusion
    • Lymphangitis cutis/pulmonis
    • Abdominal masses not confirmed and followed by imaging techniques
    • Cystic lesions
• Not a candidate for radioactive iodine I^131 therapy

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-1

Life expectancy

• At least 6 months

Hematopoietic

• WBC ≥ 3,000/mm^3
• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• Bilirubin ≤ 1.5 mg/dL
• AST and ALT ≤ 2.5 times upper limit of normal

Renal

• Creatinine ≤ 1.5 mg/dL

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No history of allergic reaction attributed to compounds of similar chemical or biologic composition to study drug
• No ongoing or active infection
• No psychiatric illness or social situation that would preclude study compliance
• No other uncontrolled illness
• No other active malignancy except nonmetastatic nonmelanoma skin cancer or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• More than 4 weeks since prior systemic cytotoxic chemotherapy (6 weeks for nitrosoureas or mitomycin)
• No more than 2 prior chemotherapy regimens for the treatment of thyroid cancer

Endocrine therapy

• Not specified

Radiotherapy

• See Disease Characteristics
• More than 4 weeks since prior external beam radiotherapy
• At least 24 weeks since prior radioactive iodine I^131 therapy

Surgery

• Not specified

Other

• Recovered from prior therapy
• More than 4 weeks since prior valproic acid or any other histone deacetylase inhibitor
• More than 4 weeks since prior investigational tumor-specific therapy
• Concurrent oral or IV bisphosphonates for bony metastases allowed at the discretion of the investigator
• No concurrent combination antiretroviral therapy for HIV-positive patients
• No other concurrent tumor-specific or investigational therapy
• No other concurrent anticancer therapy
• No concurrent adjuvant therapy for another cancer