Vectibix® (panitumumab) was non-inferior to Erbitux® (cetuximab) for overall survival in the treatment of wild-type KRAS metastatic colorectal cancer in patients who have not responded to chemotherapy, according to the results of a study presented at the ESMO 2013 Congress of the European Society for Medical Oncology in Amsterdam.

Colorectal cancer remains the second leading cause of cancer-related death in the United States. Metastatic colorectal cancer refers to cancer that has spread from the colon to distant sites in the body.

Targeted therapies are anticancer drugs that interfere with specific pathways involved in cancer cell growth or survival. Vectibix inhibits cancer cell growth and survival by targeting a protein known as the epidermal growth factor receptor (EGFR). Vectibix has been approved for the treatment of EGFR-expressing metastatic colorectal cancer that has progressed on or following fluoropyrimidine, oxaliplatin-, and irinotecan-containing chemotherapy regimens. An estimated 40-50 percent of metastatic colorectal cancers contain a in a gene known as KRAS. Vectibix appears to benefit only those patients whose cancers do not contain the mutation. This is referred to as wild-type KRAS.

This phase III trial included 999 patients with chemo-resistant wild-type KRAS metastatic colorectal cancer who were randomized to receive Vectibix or Erbitux. The prospective study showed that the median overall survival for patients treated with Vectibix was 10.4 months compared to 10 months for patients treated with Erbitux. Progression-free survival was a median of 4.1 months in patients treated with Vectibix versus 4.4 months in patients treated with Erbitux. Objective response rate, which is the percentage of patients who experienced tumor size reduction, was 22 percent for patients treated with Vectibix compared to 19.8 percent for patients treated with Erbitux.

In the safety analysis, the profiles of both treatments were consistent with previously reported studies. Adverse events (AEs) included known events such as rash, low levels of magnesium in the blood and infusion reactions.

The researchers concluded that Vectibix was non-inferior to Erbitux for the treatment of chemo-resistant wild-type KRAS metastatic colorectal cancer.

Reference:

Price T, Peeters M, Kim TW, et al. ASPECCT: a randomized, multicenter, open-label, phase 3 study of panitumumab (pmab) vs cetuximab (cmab) for previously treated wild-type (WT) KRAS metastatic colorectal cancer (mCRC). Presented at the 38th Congress of the European Society for Medical Oncology (ESMO), Amsterdam, Netherlands, September 27-October 1, 2013. Abstract 18.

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