Panitumumab after progression on cetuximab in KRAS wild-type metastatic colorectal cancer patients: a single institution experience

Tumori. 2015 Sep-Oct;101(5):524-8. doi: 10.5301/tj.5000356. Epub 2015 May 25.


Aims and background: Few data describe the activity of panitumumab after cetuximab-irinotecan-based regimen failure in patients with KRAS wild-type metastatic colorectal cancer (WT MCRC).

Methods: The aim of this study is to assess if panitumumab has some activity in this setting.

Results: We retrospectively analyzed 25 patients with KRAS WT MCRC who received panitumumab from July 2009 to January 2013 after progression on cetuximab. All patients had previously received cetuximab and irinotecan (20 patients) or oxaliplatin (5 patients). We withdrew cetuximab for intolerance in 4 patients (16%). Twenty-one patients (84%) who had previously responded to cetuximab (overall response rate [ORR] plus stable disease ≥5 months) received panitumumab off-label after progression on cetuximab because they were strongly motivated to continue treatment without chemotherapy. The median number of cycles of panitumumab was 7 (range 1-54). Only 20 patients were evaluable for ORR (5 patients received 1-2 cycles and then died). We observed 1 (5%) partial response, 5 (25%) stable disease, median duration 9 months. Median progression-free survival (PFS) and overall survival (OS) were 5 (3-28) and 8 (5-41) months, respectively. All patients were evaluable for toxicity. No patients developed anemia or neutropenia. One patient (4%) developed grade 2 thrombocytopenia, 8 patients (32%) grade 2-3 dry skin or rash, and 2 patients (8%) grade 2 nausea-vomiting (Common Terminology Criteria for Adverse Events version 4.03).

Conclusions: Our data, with all the limits of a retrospective analysis, show longer PFS and OS as compared to other series in the same setting, demonstrating that panitumumab has treatment effectiveness in patients with KRAS WT MCRC who progressed on prior cetuximab. Further confirmatory prospective studies with a larger series of patients are necessary.

MeSH terms

  • Adult
  • Aged
  • Antibodies, Monoclonal / administration & dosage
  • Antibodies, Monoclonal / adverse effects
  • Antibodies, Monoclonal / therapeutic use*
  • Antineoplastic Agents / administration & dosage
  • Antineoplastic Agents / adverse effects
  • Antineoplastic Agents / therapeutic use*
  • Cetuximab / therapeutic use*
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / pathology
  • Disease Progression
  • Disease-Free Survival
  • Female
  • Humans
  • Liver Neoplasms / drug therapy*
  • Liver Neoplasms / secondary
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / secondary
  • Male
  • Middle Aged
  • Panitumumab
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins p21(ras)
  • Retrospective Studies
  • Treatment Outcome
  • ras Proteins / genetics*


  • Antibodies, Monoclonal
  • Antineoplastic Agents
  • KRAS protein, human
  • Proto-Oncogene Proteins
  • Panitumumab
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins
  • Cetuximab