INCLUSION CRITERIA

   - Squamous cell carcinoma of the skin or "unknown primary lesions" at the time of
   diagnosis if metastatic disease present with a history of plausible primary skin site
   removed in the past. Example: squamous cell carcinoma in neck or parotid lymph nodes
   with no identifiable mucosal primary but with a history of the removal of one or more
   early stage squamous cell carcinomas of the skin in an anatomically relevant lymphatic
   drainage region would be eligible

   - Measurable disease, defined as at least 1 lesion that can be accurately measured in at
   least 1 dimension as ≥ 10 mm with computed tomography (CT) scan; magnetic resonance
   imaging (MRI); or calipers during clinical exam

   - Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (Karnofsky ≥ 60%)

   - Life expectancy greater than 3 months

   - Absolute neutrophil count ≥ 1,000/mcL

   - Platelets ≥ 100,000/mcL

   - Total bilirubin

      - Within normal institutional limits OR

      - ≤ 2 x upper limit of normal (ULN) if participant has Gilbert's syndrome (elevated
      unconjugated bilirubin from decreased UDP glucuronosyltransferase 1 family,
      polypeptide A1 [UGT1A1] activity)

   - Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase
   [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT])
   ≤ 2.5 x institutional ULN or up to 5 X ULN if known to be caused by liver metastases

   - Creatinine OR

      - < 1.3 mg/dL OR

      - Creatinine clearance ≥ 30 mL/min/1.73 m2 for patients with creatinine levels
      above institutional normal (Note creatinine clearances between 30 and 49 mg/dL
      necessitate dose modification)

   - For participants with a history of coronary artery disease (CAD)/myocardial infarction
   (MI) or congestive heart failure (CHF), ejection fraction (EF) ≥ 50% by multi-gated
   acquisition (MUGA) or echocardiogram (exceptions by PI discretion)

EXCLUSION CRITERIA

   - Prior treatment with systemic capecitabine or prodrugs

   - Prior treatment with systemic fluorouracil (5-FU) or prodrugs (prior topical treatment
   with 5FU is permitted if recovered from any toxicities > grade 1, and after at least 5
   half-lives of the last systemically administered agent have passed)

   - Receiving any other investigational agents or anti-cancer treatments

   - Candidates for curative locoregional treatment (patients with recurrent locoregional
   disease following surgery and/ or radiation for which a resection is unacceptably
   morbid and unlikely to be curative are eligible)

   - History of allergic reactions attributed to compounds of similar chemical or biologic
   composition to capecitabine

   - Uncontrolled concurrent illness including, but not limited to:

      - Ongoing or active infection

      - Symptomatic congestive heart failure

      - Unstable angina pectoris

      - Cardiac arrhythmia

      - Psychiatric illness/social situations that would limit compliance with study
      requirements

   - Pregnant

   - Lactating