Researchers involved in an international randomized trial have reported that the addition of Vectibix® (panitumumab) to FOLFIRI (5-fluorourcil, Camptosar® [irinotecan], and leucovorin) improves progression-free survival (PFS) in patients with colorectal cancer with wild-type KRAS receiving second-line therapy. The details of this study were presented at the Joint ECCO 15-34th ESMO Congress in Berlin, September 20-24.[1]
Vectibix is the first entirely humanized monoclonal antibody targeting the epidermal growth factor receptor (EGFR). Vectibix is approved for EGFR-expressing, metastatic colorectal cancer that has progressed while on treatment or following therapy with fluoropyrimidine-, oxaliplatin-, and irinotecan-containing chemotherapy regimens. Previous studies have shown that Vectibix provides clinical benefit in a significant portion of patients with metastatic colorectal cancer whose disease has failed standard chemotherapy.
Researchers from Northwestern University have previously reported that the combination of the Vectibix and FOLFIR shows promising results for the initial treatment of metastatic colorectal cancer.
It is estimated that between 30-40% of all patients with colorectal cancers have a KRAS mutation that would ultimately render them ineligible for EGFR-targeted therapy. Patients with normal KRAS tend to have a disruption of cellular growth signaling through the EGFR pathway and are responsive to targeted therapies. However, KRAS mutations allow growth signaling within the EGFR to continue, even in the presence of EGFR-targeted agents.
This study included 1,186 patients with metastatic colorectal cancer who had failed first-line therapy. This study originally targeted all patients with colorectal cancer failing first line therapy but was modified to focus on patients with wild-type KRAS. 1,083 patients in this study had KRAS results; 55% were wild-type, and 45% were mutant-type.
- For patients with wild-type KRAS, PFS was 5.9 months for the Vectibix arm and 3.9 months for the control arm (p=0.004).
- For patients with wild type KRAS, the response rate was 35% compared with 10% in the control group.
- For patients with wild-type KRAS, median overall survival (OS) was 14.5 months for the Vectibix arm and 12.5 months for the control arm (p=0.115).
- Vectibix did not improve PFS, OS, or response rate in patients with mutated KRAS.
Comments: This study shows the importance of KRAS mutations in outcomes of patients treated with Vectibix.
Reference:
[1] Peeters M, Price T, Hotko Y, et al. Randomized phase 3 study of panitumumab with FOLFIRI vs FOLFIRI alone as second-line treatment (tx) in patients (pts) with metastatic colorectal cancer (mCRC). European Journal of Cancer Supplements. 2009;7:9, abstract 14LBA.
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