Maintenance Panitumumab vs Panitumumab/Fluorouracil/Leucovorin in RAS Wild-Type Metastatic Colorectal Cancer


Key Points

  • Panitumumab plus fluorouracil/leucovorin was associated with better progression-free survival vs panitumumab alone.
  • Combination treatment was associated with an increased incidence of grade ≥ 3 adverse events.

In an Italian phase II trial reported in JAMA Oncology, Pietrantonio et al found that maintenance panitumumab alone was inferior in terms of progression-free survival (PFS) compared to maintenance panitumumab plus fluorouracil/leucovorin in RAS wild-type metastatic colorectal cancer.

Study Details

In the open-label, multicenter, noninferiority trial, patients with previously untreated metastatic disease were randomly assigned between July 2015 and October 2017 to receive maintenance therapy with panitumumab alone (n = 112) or panitumumab plus fluorouracil/leucovorin (n = 117) after 4-month induction with panitumumab plus FOLFOX4 (oxaliplatin, leucovorin, and fluorouracil). Maintenance treatment was continued until disease progression or unacceptable toxicity.

The primary endpoint was 10-month PFS analyzed on intention-to-treat basis with a noninferiority margin of 1.515 for the upper limit of the 1-sided 90% confidence interval (CI) of the hazard ratio (HR) for panitumumab alone vs combination treatment.


Median follow-up was 18.0 months. Noninferiority of panitumumab alone was not shown (upper limit of 1-sided 90% CI of the HR = 1.857). PFS at 10 months was significantly better in the combination group (49.0% for panitumumab alone vs 59.9% for the combination, HR = 1.51, P = .01). Median PFS was 9.9 vs 12.0 months (P = .006).


During maintenance therapy, treatment-related grade ≥ 3 adverse events occurred in 20.3% of the panitumumab group vs 42.4% of the combination group. The combination group had higher rates of diarrhea (any grade = 24.7% vs 10.1%; grade ≥ 3 = 4.7% vs 1.3%) and stomatitis (any grade = 32.9% vs 7.6%; grade ≥ 3 = 7.1% vs 1.3%).

The investigators concluded, “In patients with RAS wild-type metastatic colorectal cancer, maintenance therapy with single-agent panitumumab was inferior in terms of [PFS] compared with panitumumab plus fluorouracil/leucovorin, which slightly increased the treatment toxic effects.”

Filippo Pietrantonio, MD, of Istituto Nazionale dei Tumori, Milan, is the corresponding author for the JAMA Oncology article.

Disclosure: The study was supported by Amgen. For full disclosures of the study authors, visit

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