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Panitumumab noninferior to cetuximab in chemotherapy-refractory colorectal cancer
Panitumumab and cetuximab conferred similar OS benefits and demonstrated comparable safety profiles in patients with chemotherapy-refractory, wild-type KRAS exon 2 metastatic colorectal cancer, according to phase 3 study results.
The multicenter, open-label analysis evaluated the two anti-EGFR monoclonal antibodies in 999 patients with an ECOG performance status of ≤2.
Researchers randomly assigned 499 patients 6 mg/kg panitumumab (Vectibix, Amgen) every 2 weeks. The remaining 500 patients received a 400 mg/m2 loading dose of cetuximab (Erbitux; Bristol-Myers Squibb, Lilly), followed by 250 mg/m2 weekly.
Researchers calculated a –3.19 z score for OS, demonstrating panitumumab’s noninferiority to cetuximab (P=.0007). They also found panitumumab retained 105.7% (95% CI, 81.9-129.5) of cetuximab’s effect on OS demonstrated in the study.
Results indicated median OS of 10.4 months for the panitumumab arm and 10 months for the cetuximab (HR=0.97; 95% CI, 0.84-1.11).
In general, incidence of adverse events of any grade was comparable between arms. Grade 3 to grade 4 skin toxicity occurred in 13% of patients assigned panitumumab and 10% of those assigned cetuximab. More patients assigned cetuximab experienced grade 3 to grade 4 infusion reaction (2% vs. ˂.5%), whereas grade 3 to grade 4 hypomagnesaemia was more common in the panitumumab arm (7% vs. 3%).
One patient died in the cetuximab arm due to a treatment-related lung infection.
“In view of the consistency in efficacy and toxicity seen, small but meaningful differences in [grade 3 to grade 4] infusion reactions and differences in dose scheduling can guide physician choice of anti-EGFR treatment,” the researchers concluded.
Disclosure: The study was funded by Amgen. See the study for a full list of the researchers’ relevant financial disclosures.