Capecitabine in Treating Patients With Advanced or Recurrent Squamous Cell Carcinoma of the Skin

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