Chemotherapy plus bevacizumab (Avastin) for metastatic colorectal cancer. Which is the best combination?

This study compared two strategies for treating patients with metastatic colorectal cancer (colorectal cancer that has spread to distant sites).

Bevacizumab is an anti-cancer drug that blocks the formation of new blood vessels needed for the cancer to grow and spread. Combined with chemotherapy it is a standard first treatment option for patients with metastatic colorectal cancer.

The chemotherapy treatment usually includes a combination of 5-fluorouracil (Efudex) and leucovorin plus oxaliplatin (Eloxatin; FOLFOX) or irinotecan (Camptosar; FOLFIRI). Combining 5-fluorouracil and leucovorin with oxaliplatin plus irinotecan (FOLFOXIRI) may improve patient outcome.

508 patients with metastatic colorectal cancer were randomly assigned to two treatment groups. Group 1 received FOLFIRI plus bevacizumab. Group 2 received FOLFOXIRI plus bevacizumab. The time until cancer progression and patient survival was assessed for both groups.  

The risk of the cancer progressing was 25% lower for patients receiving FOLFOXIRI, compared to patients receiving FOLFIRI. The cancer did not progress for an average of 12.1 months for patients in group 2, compared with 9.7 months for patients in group 1.

There was a trend towards better survival for patients receiving FOLFOXIRI, compared to patients receiving FOLFIRI. At the end of the study 48% of patients in group 2 were still alive compared to 39.5% of patients in group 1.

The rates of severe adverse (negative) events were similar in both groups, 19.7% of patients in group 1 and 20.4% of patients in group 2. However, group 2 had higher rates of diarrhea (18.8% compared to 10.6%), stomatitis (inflammation of the mouth and lips; 8.8% compared to 4.3%) and neutropenia (low levels of specific white blood cells [neutrophils] needed to fight infections; 50% compared to 20.5%).

The authors concluded that FOLFOXIRI plus bevacizumab improved patient outcome, compared to FOLFIRI plus bevacizumab. However, they also highlight that FOLFOXIRI leads to higher rates of certain adverse events.