Systematic review and economic evaluation of bevacizumab and cetuximab for the treatment of metastatic colorectal cancer.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of bevacizumab and cetuximab in the treatment of individuals with metastatic colorectal cancer (CRC).

DATA SOURCES

Searches of main electronic databases were conducted in April and May 2005.

REVIEW METHODS

For the assessment of bevacizumab, trials were included if they recruited participants with untreated metastatic CRC for first-line treatment. Only trials comparing bevacizumab in combination with irinotecan and/or established fluorouracil (5-FU)-containing or releasing regimens given as first-line therapy were included. For the assessment of cetuximab, trials were included if they recruited participants with epidermal growth-factor receptor-expressing metastatic CRC who had previously failed irinotecan-including therapy. Independent cost-effectiveness models of bevacizumab and cetuximab were developed using survival modelling methods.

RESULTS

Adding bevacizumab to irinotecan in combination with 5-FU/folic acid (FA) plus irinotecan resulted in a statistically significant increase in median overall survival (OS) of 4.7 months. Adding bevacizumab to 5-FU/FA resulted in a non-significant increase in median OS of 3.7 months within one study and 7.7 months in another. Adding bevacizumab to irinotecan, fluorouracil and leucovorin (IFL) resulted in a statistically significant increase in median progression-free survival (PFS) of 4.4 months. Adding bevacizumab to 5-FU/FA resulted in a statistically significant increase in median PFS of 3.7 months, and a statistically significant increase in time to disease progression of 3.8 months compared to FU/FA alone. An overall tumour response rate of 44.8% was reported for bevacizumab plus IFL compared to 34.8% for IFL plus placebo. This addition was statistically significant. The addition of bevacizumab to 5-FU/FA resulted in a significant difference in tumour response rate within one study, but not another. Bevacizumab in combination with IFL or 5-FU/FA was observed to result in an increase of grade 3/4 adverse events. The independent health economic assessment suggests that the cost-effectiveness of bevacizumab plus IFL is unlikely to be better than pound 46,853 per life-year gained (LYG); the cost-utility of bevacizumab plus IFL is unlikely to be better than pound 62,857 per quality-adjusted life-year (QALY) gained. The cost-effectiveness of bevacizumab plus 5-FU/FA versus 5-FU/FA is unlikely to be better than pound 84,607 per LYG; the cost-utility of bevacizumab plus 5-FU/FA versus 5-FU/FA is unlikely to be better than pound 88,658 per QALY gained. A Phase II trial reported a median OS duration of 8.6 months for patients receiving cetuximab plus irinotecan, plus a median time to progression of 4.1 months, a tumour response rate of 22.9% and suggested that treatment with cetuximab in combination with irinotecan is associated with significantly more adverse events (any grade 3 or grade 4 adverse event) than cetuximab monotherapy. The single arm study of cetuximab plus irinotecan reported a median OS duration of 8.4 months, a median time to progression of 2.9 months and a tumour response rate of 15.2%. The cost-effectiveness model suggested that the expected survival duration of patients receiving cetuximab plus irinotecan is 0.79 years (9.5 months) when the proposed continuation rule is applied. In order for cetuximab plus irinotecan to achieve a cost-utility ratio of pound 30,000 per QALY gained, treatment with cetuximab plus irinotecan must provide an additional 0.65 life years (7.8 months) over treatment with active/best supportive care, implying that survival in the active/best supportive care group must be 0.14 life years (1.7 months) or less.

CONCLUSIONS

The trials indicate that bevacizumab in combination with 5-FU/FA, and bevacizumab in combination with IFL, is clinically effective in comparison to standard chemotherapy options for the first-line treatment of metastatic CRC. The health economic analysis suggests that the marginal cost-utility of bevacizumab plus IFL versus IFL is unlikely to be better than pound 62,857 per QALY gained, and the marginal cost-utility of bevacizumab plus 5-FU/FA versus 5-FU/FA is unlikely to be better than pound 88,658 per QALY gained. There is no direct evidence to demonstrate whether cetuximab in combination with irinotecan improves health-related quality of life or OS in comparison to active/best supportive care or oxaliplatin plus 5-FU/FA, although the evidence on tumour response rates suggests that cetuximab plus irinotecan has some clinical activity. While it is difficult to suggest whether cetuximab represents value for money, indirect comparisons suggest that the incremental cost-utility of cetuximab plus irinotecan is unlikely to be better than pound 30,000 per QALY gained. This review highlights a number of areas for further research, including clarifying the true impact of first-line bevacizumab in combination with irinotecan and/or infusional 5-FU/FA, without subsequent bevacizumab treatment following disease progression, on OS in patients with metastatic CRC who are representative of the typical population of CRC patients in England and Wales. Further research concerning the impact of therapies on health-related quality of life is essential.