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

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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.

PFS

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).

Toxicity

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 jamanetwork.com.

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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