SOX or CapeOX: comparing two chemotherapy regimens for the treatment of metastatic colorectal cancer

This study compared disease progression and overall survival of metastatic colorectal cancer patients who underwent two different chemotherapy regimens. 

Metastatic colorectal cancer indicates that the cancer has spread from its original site in the bowel to distant tissues or organs. The most commonly prescribed chemotherapy for patients with colorectal cancer is 5-fluorouracil (Efudex). It is normally administered by continuous injection over a number of days using a pump. Although this is effective it is inconvenient and unsafe for patients.

Newer medications have been developed that are similar to 5-fluorouracil but can be taken by mouth; capecitabine (Xeloda) and S-1 (S-1). Previous studies have shown that these drugs can be combined with oxaliplatin (Eloxatin) to treat metastatic colorectal cancer: capecitabine plus oxaliplatin (CapeOX or Xelox) or S-1 plus oxaliplatin (SOX). It is not yet known whether SOX is as effective as CapeOX for the treatment of metastatic colorectal cancer.

This trial included 2 groups of patients with metastatic colorectal cancer. Group 1 was treated with CapeOX (161 patients) and group 2 was treated with SOX (164 patients). CapeOX treatment involved taking 1000 mg/m² of capecitabine twice per day on days 1 to 14 and 130mg/m² of oxaliplatin on day 1. SOX treatment involved taking 40mg/m² of S-1 twice per day on days 1 to 14 and 130mg/m² of oxaliplatin on day 1. This treatment regimen was repeated up to 9 times. The progression-free survival time (time following treatment before the disease progresses) and overall survival time (time until death from any cause) was assessed for each patient.

The average overall-survival was 19.1 months for patients receiving SOX treatment and 17.6 months for patients receiving CapeOX treatment. The average progression-free survival time was 6.9 months for patients receiving SOX treatment and 6.3 months for patient receiving CapeOX. After the cancer had progressed patients had a similar overall-survival time; 9.3 months for the SOX group and 9.6 months for the CapeOX group.

The efficacy of the treatment was not affected by patient age, sex, activity levels, previous treatment, or the site or number of metastatic sites. 

The authors concluded that SOX and CapeOX had similar efficacy in this patient group. They suggest that the SOX regimen can be used as an alternative treatment option for patients with metastatic colorectal cancer.