Rechallenge for Patients With RAS and BRAF Wild-Type Metastatic Colorectal Cancer With Acquired Resistance to First-line Cetuximab and Irinotecan: A Phase 2 Single-Arm Clinical Trial

JAMA Oncol. 2019 Mar 1;5(3):343-350. doi: 10.1001/jamaoncol.2018.5080.


Importance: Based on a small retrospective study, rechallenge with cetuximab-based therapy for patients with KRAS wild-type metastatic colorectal cancer (mCRC) who were previously treated with the same anti-epidermal growth factor receptor-based regimen might be efficacious. Recent data suggest the role of liquid biopsy as a tool to track molecular events in circulating tumor DNA (ctDNA).

Objective: To prospectively assess the activity of cetuximab plus irinotecan as third-line treatment for patients with RAS and BRAF wild-type mCRC who were initially sensitive to and then resistant to first-line irinotecan- and cetuximab-based therapy.

Design, setting, and participants: Multicenter phase 2 single-arm trial conducted from January 7, 2015, to June 19, 2017. Liquid biopsies for analysis of ctDNA were collected at baseline. Main eligibility criteria included RAS and BRAF wild-type status on tissue samples; prior first-line irinotecan- and cetuximab-based regimen with at least partial response, progression-free survival of at least 6 months with first-line therapy, and progression within 4 weeks after last dose of cetuximab; and prior second-line oxaliplatin- and bevacizumab-based treatment.

Interventions: Biweekly cetuximab, 500 mg/m2, plus irinotecan, 180 mg/m2.

Main outcomes and measures: Overall response rate according to the Response Evaluation Criteria in Solid Tumors, version 1.1. Secondary end points included progression-free survival and overall survival and, as an exploratory analysis, RAS mutations in ctDNA.

Results: Twenty-eight patients (9 women and 19 men; median age, 69 years [range, 45-79 years]) were enrolled. Six partial responses (4 confirmed) and 9 disease stabilizations were reported (response rate, 21%; 95% CI, 10%-40%; disease control rate, 54%; 95% CI, 36%-70%). Primary end point was met because lower limit of 95% CI of response rate was higher than 5%. RAS mutations were found in ctDNA collected at rechallenge baseline in 12 of 25 evaluable patients (48%). No RAS mutations were detected in samples from patients who achieved confirmed partial response. Patients with RAS wild-type ctDNA had significantly longer progression-free survival than those with RAS mutated ctDNA (median progression-free survival, 4.0 vs 1.9 months; hazard ratio, 0.44; 95% CI, 0.18-0.98; P = .03).

Conclusions and relevance: This is the first prospective demonstration that a rechallenge strategy with cetuximab and irinotecan may be active in patients with RAS and BRAF wild-type mCRC with acquired resistance to first-line irinotecan- and cetuximab-based therapy. The evaluation of RAS mutational status on ctDNA might be helpful in selecting candidate patients.

Trial registration: Identifier: NCT02296203.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Biomarkers, Tumor / genetics*
  • Cetuximab / administration & dosage*
  • Cetuximab / adverse effects
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / mortality
  • Colorectal Neoplasms / pathology
  • Disease Progression
  • Drug Resistance, Neoplasm*
  • Female
  • Genes, ras*
  • Humans
  • Irinotecan / administration & dosage*
  • Irinotecan / adverse effects
  • Italy
  • Male
  • Middle Aged
  • Progression-Free Survival
  • Prospective Studies
  • Proto-Oncogene Proteins B-raf / genetics*
  • Risk Factors
  • Time Factors


  • Biomarkers, Tumor
  • Irinotecan
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Cetuximab

Associated data