Colorectal cancer (CRC) in Egypt is advanced tumors at diagnosis. Although, the dramatic increase in efficacy, reduction of mortality, and improvements in survival by the use of standard doses of chemotherapy, some CRC patients suffer from severe toxicities besides disease progression. Use of chemotherapy less than the maximum tolerated dose, with no prolonged drug free breaks incapacitates the cells to engage in progression mechanisms, suggesting that it could be a better alternative to standard dose therapy with better toxicity profile

This is a randomized phase II prospective study that included 70 (35 in each arm) metastatic Egyptian CRC cancer patients diagnosed at the National Cancer Institute, Cairo University between January 2016 and June 2018). Patients were randomly treated with either classic XELOX (arm A) or with capecitabine (2000 mg daily x 8 weeks) and oxaliplatin (30 mg/m2 weekly X 8 weeks) then 2 weeks rest (arm B). Toxicities and the survival analysis after two years for both regimens were recorded. Blood samples are taken from both groups to assess pharmacokinetics of capecitabine and its relation to dosing.

Inclusion Criteria:

• Patient age 18-70 years of both sexes.
• PS 0-2 and histologically proven mCRC with unresectable metastases (rectal cancer is included to left side cancers).
• They should have measurable lesions (that can be accurately measured in at least one dimension using calipers or ruler and measurement must be at least 20 mm using conventional techniques or 10 mm using spiral CT scan).
• No previous treatment for metastatic disease and had ended adjuvant treatment > 6 months.
• peripheral neuritis less than grade 2.
• Normal organ functions:(Creatinine ≤1.2, Bilirubin ≤1.2, SGOT/SGPT< 2N, HB >9gm/dl, WBC>3.5/dl with ANC >1.5/dl, Plat ≥100/dl).
• For patients with liver metastases, Bilirubin should not be >2.5N and transaminases not >5N. (All patients were screened for HCV and HBS Ag by PCR).
• Adequate cardiac functions (EF>55%)

Exclusion Criteria:

• patients with only ascites or bone metastasis