Patients with advanced colorectal cancer whose tumors have gotten smaller six weeks after starting treatment with Erbitux had a much longer time before their cancer got worse and almost twice the overall survival as patients whose tumors didn’t shrink.
Patients in the BOND study had already gotten worse on standard chemotherapy and were receiving either Erbitux® (cetuximab) alone or in combination with irinotecan. CT scans for about a third of them showed at least a 10 percent decrease in the size of their tumors six weeks into treatment.
Of 289 patients in the study, 99 or 34 percent had tumor size decrease at the six-week scan, 190 or 66 percent showed no change.
Comparing those who responded to treatment at six weeks with those who didn’t:
- Median time to progression was 6.1 months compared to 1.5 months.
- Overall survival was 13.7 months compared to 6.9 months.
In predicting long-term outcome, early tumor shrinkage was more important than skin rash, another way of estimating how well Erbitux is working.
H. Piessevaux and the study team in Belgium concluded,
Tumor shrinkage at 6 weeks is a strong predictor of time to progression and overall survival in metastatic colorectal cancer patients treated with cetuximab with or without irinotecan. This suggests early tumor shrinkage is the hallmark of efficacy of cetuximab and reliably identifies the subpopulation that is sensitive to the drug. Early tumor shrinkage can be used as a marker of efficacy in clinical practice, as such or in combination.
SOURCE: Piessevaux et al., Annals of Oncology, Volume 20, Number 8, August 2009.