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Panitumumab found effective and well tolerated in chemotherapy-refractory mCRC


The authors describe the results of a study assessing the efficacyof panitumumab in patients with metastatic colorectal cancer who haveprogressed after standard chemotherapy.

Panitumumab is ahuman monoclonal antibody directed against the epidermal growth factorreceptor (EGFR), which has demonstrated activity in refractorycolorectal cancer in phase II studies. This phase III trial included463 patients with colorectal cancer who had documented diseaseprogression during or within six months following the lastadministration of chemotherapy (fluoropyrimidine, irinotecan, andoxaliplatin). Participants were randomised to panitumumab 6mg/kg everytwo weeks plus best supportive care (BSC; n=231) or BSC alone (n=232).The primary endpoint of the study was progression-free survival (PFS);secondary endpoints included objective response, overall survival (OS),and safety.

The main results were as follows:

•Median PFS was eight weeks (95% CI 7.9–8.4) for panitumumab and 7.3weeks (95% CI 7.1–7.7) for BSC (hazard ratio 0.54; 95% CI 0.44–0.66,p<0.0001). The mean (standard error) PFS was 13.8 (0.8) weeks forpanitumumab and 8.5 (0.5) weeks for BSC.

• After a 12-month minimum follow-up, response rates were 10% for panitumumab and 0% for BSC (p<0.0001).

• There was no difference between the two groups in OS (hazard ratio1.00; 95% CI 0.82–1.22); however, this was confounded by crossover ofpatients from BSC to panitumumab in a crossover study.

Theauthors conclude: “This study demonstrates that panitumumab given everytwo weeks is effective and well tolerated in patients with advancedcolorectal cancer that had progressed after standard chemotherapy.Panitumumab represents a new treatment option that can improve PFS withmanageable toxicity in patients with chemorefractory metastaticcolorectal cancer. These results warrant investigation of panitumumabin combination with earlier lines of therapy in colorectal cancer.”

J Clin Oncol 2007;25(13):1658-64


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