Inclusion Criteria:

- 18 years of age or older.

- Cancer of the thyroid confirmed by a biopsy sample. Specific types of thyroid cancer
included in this study are anaplastic, differentiated (papillary, follicular, or
Hürthle cell), and medullary thyroid cancers.

- For patients with differentiated (papillary, follicular, or Hürthle cell) thyroid
cancer, no more than 1 prior chemotherapy treatment is allowed.

- Measurable disease is required (at least one lesion at least 2 cm in length by
conventional computed tomography (CT) techniques or at least 1 cm by spiral CT scan).

- Any prior chemotherapy or radiation therapy must be stopped at least 4 weeks before
the first dose of study treatment. Prior radioiodine (I131) therapy must be stopped
at least 3 (or 6) months before first dose of study treatment (depending on
responsiveness to this therapy).

- Recovery from any toxic effects of prior chemotherapy, radiation therapy and surgery.

- Patients with reproductive potential must use a medically acceptable contraceptive
method. Women of childbearing potential must have a negative pregnancy test at
screening.

Exclusion Criteria:

- History of retinopathy.

- Serious ongoing medical or psychiatric disorder (as determined by the clinical
investigator).

- External beam radiation therapy to >30% of the bone marrow at any time prior to study
entry.

- Prior treatment with irofulven or capecitabine, or protracted infusion of
5-fluorouracil (5-FU) (infusion duration greater than or equal to 5 days) or other
fluoropyrimidines.

- Therapeutic doses of coumarin derivatives (warfarin) 14 days prior to receiving the
first dose of study treatment or during the study period.

Please note: There are additional criteria that must be met in order to be eligible for
this study.