Capecitabine and Celecoxib in Patients With Solid Cancers That Have Been Previously Treated With Standard Therapies

Inclusion Criteria:

* Histologically or cytologically confirmed solid tumor that is metastatic or unresectable and for which standard curative or palliative measures do not exist or are no longer effective

OR

Histologically or cytologically confirmed solid tumor for which single agent capecitabine is an appropriate treatment option.

* Eastern Cooperative Oncology Group (ECOG) performance status =\< 1
* Life expectancy \> 3 months
* Absolute neutrophil count (ANC) \>= l500/ul
* Hemoglobin \>= 9g/dL
* Platelets \>= 100,000/ul
* Creatinine within institutional normal limits or glomerular filtration rate \>= 50 mL/min/1.73 m\^2 by Chronic Kidney Disease Epidemiology Collaboration (CKD EPI) equation
* Total bilirubin \< 1.5 x upper limit of normal
* Serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvate transaminase (SGPT) \< 2.5 x upper limit of normal for patients without liver metastases OR SGOT and SGPT \< 5 x upper limit of normal for patients with liver metastases
* Measurable or non-measurable disease will be allowed
* Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation, up until 30 days after final study treatment; should a woman become pregnant or suspect that she is pregnant while participating in this study, she should inform her treating physician immediately
* Patients taking substrates of CYP2C9 should be encouraged to switch to alternative drugs whenever possible, given the potential for drug-drug interactions with the study drugs
* Signed informed consent

Exclusion Criteria:

* Prior treatment with capecitabine and/or celecoxib is allowed; however, patients with a documented history (at the time of enrollment) of \>= grade 3 toxicities with capecitabine or celecoxib are excluded
* Patients taking any of the following drugs are excluded: inducers or inhibitors of CYP2C9, warfarin, aspirin, corticosteroids, or non-steroidal anti-inflammatory drugs (NSAIDs)
* History of myocardial infarction or stroke within the last 6 months, or history of uncontrolled cardiovascular or cerebrovascular disease; a 12-lead electrocardiogram (ECG) will be performed during the screening period
* History of perforation or bleeding related to peptic ulcer disease
* History of hypersensitivity or allergy to study drugs, aspirin, sulfonamides, or NSAIDs
* Known poor metabolizers of CYP2C9 substrates
* Known deficiency of dihydropyrimidine dehydrogenase (DPD)
* Patients who have had chemotherapy, immunotherapy, or investigational anti-cancer therapy within 4 weeks of starting study drug, or radiotherapy within 14 days of starting study drug, or those who have not recovered from adverse events due to agents administered more than 4 weeks earlier
* Patients may not be receiving any other investigational agents or any concomitant antineoplastic therapy, with the exception of androgen ablating agents (for patients with prior prostate cancer)
* Serious underlying medical or psychiatric illnesses that would, in the opinion of the treating physician, substantially increase the risk for complications related to treatment; similarly, any unstable medical condition that in the opinion of the treating physician or study investigators, would interfere with determination of the study objectives
* Pregnancy or breastfeeding
* Major surgery within 4 weeks