Sulfasalazine in Patients With Metastatic Colorectal Cancer

Inclusion Criteria: 1. Histologically confirmed diagnosis of stage IV (metastatic) colorectal cancer. Staging will be performed according to the American Joint Committee on Cancer (AJCC) 8th edition and will be documented by all investigating parameters of metastatic colorectal cancer 2. Male or female patients with age range from 18-65 years old 3. Women of childbearing age will be required to be on acceptable forms of contraception 4. Performance status \< 2 according to the Eastern Cooperative Oncology Group (ECOG) score 5. No contraindication to chemotherapy (absence of myelosuppression) 6. Adequate liver function (alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \< grade 2) according to the National Cancer Institute-Common Terminology Criteria for Adverse Events, version 5.0 (NCI-CTCAE v 5.0) 7. Adequate renal function (estimated creatinine clearance (eCrCl), serum creatinine (SCr) \< grade 2) according to NCI-CTCAE, v 5.0 8. Adequate hematological parameters (hemoglobin, erythrocytes, platelets, leukocytes and absolute neutrophil count (ANC) \< grade 2 according to NCI-CTCAE, v 5.0 Exclusion Criteria: 1. Pregnant or lactating women 2. Patients with concurrent active cancer originating from a primary site other than the colon or rectum 3. Patients who have known allergy to sulfasalazine or its metabolites 4. Patients with nephrolithiasis, severe vomiting or severe diarrhea 5. Patients who are receiving highly plasma protein-bound drugs or drugs with extensive hepatic metabolism such as; coumarin anti-coagulants 6. Patients with intestinal or urinary obstruction 7. Patients with known glucose-6-phosphate dehydrogenase deficiency or porphyria 8. Ongoing treatment with sulfasalazine or mesalamine for ulcerative colitis or rheumatoid arthritis