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Phase II and III Trials Support First-Line Panitumumab in Combination With FOLFOX in Wild‑Type RAS Metastatic Colorectal Cancer

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Key Points

  • In the PEAK trial, treatment with panitumumab plus FOLFOX resulted in earlier tumor shrinkage and significantly longer and deeper durations of response than with bevacizumab.
  • Overall response rates appeared to be similar between the panitumumab and bevacizumab arms.
  • In a separate analysis of the phase III PRIME study, there were no significant differences in quality of life among patients treated with panitumumab plus FOLFOX vs FOLFOX alone.

New data from the phase II PEAK and phase III PRIME studies support the first-line use of panitumumab (Vectibix) in combination with FOLFOX (fluorouracil, leucovorin, oxaliplatin) in patients with wild-type RAS metastatic colorectal cancer. The study results were presented during a poster session at the 2015 Gastrointestinal Cancers Symposium (Abstract 660 and Abstact 537).

PEAK Study

The phase II PEAK trial was designed to compare the efficacy of first-line panitumumab vs bevacizumab (Avastin) in combination with modified FOLFOX6 in previously untreated patients with wild-type KRAS exon 2 metastatic colorectal cancer. Primary endpoints include progression-free survival, and secondary endpoints include overall survival, objective response, duration of response, depth of response, and safety.

In an exploratory analysis, treatment with panitumumab compared to bevacizumab resulted in a significantly higher proportion of patients with earlier tumor shrinkage at week 8 (64% vs 45%, respectively; P = .0232). Responding patients experienced a significantly longer duration of response with panitumumab than with bevacizumab (11.4 vs 8.5 months, respectively; P = .0142) and greater depth of response (65% vs 46%, respectively; P = .0007).

Overall response rates appeared to be similar between panitumumab and bevacizumab. This is consistent with observed overall survival and progression-free survival rates, and with data previously reported. The safety profile of panitumumab was consistent with previously reported studies.

While the primary analysis from PEAK showed similar overall response rates between the panitumumab- and bevacizumab-based regimens, this exploratory analysis demonstrates that panitumumab produces early, sustained antitumor activity, which may in part explain the survival benefits seen with panitumumab vs bevacizumab in this trial.

PRIME Study

The phase III PRIME study was designed to evaluate panitumumab in combination with FOLFOX vs FOLFOX alone in patients with wild-type KRAS exon 2 metastatic colorectal cancer. The primary endpoint was progression-free survival. A separate analysis of quality-adjusted survival demonstrated that there were no significant differences in quality of life among patients treated with panitumumab plus FOLFOX vs FOLFOX alone despite the incidence of adverse events associated with each treatment regimen. The quality-of-life analysis included a scale that assessed mobility, self-care, usual activities, pain/discomfort, and anxiety/depression.

The studies were sponsored by Amgen. For full disclosures of the study authors, view the study abstracts at abstract.asco.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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