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Original Investigation
November 21, 2018

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

Author Affiliations
  • 1Unit of Medical Oncology 2, Department of Translational Research and New Technologies in Medicine and Surgery, Azienda Ospedaliera Universitaria Pisana, Pisa, Italy
  • 2Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy
  • 3Medical Oncology Unit 1, Clinical and Experimental Oncology Department, Veneto Institute of Oncology Istituto Oncologico Veneto–Istituto di Ricovero e Cura a Carattere Scientifico, Padua, Italy
  • 4Department of Diagnostic Pathology and Laboratory Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
  • 5Clinical Pharmacology and Pharmacogenetics Unit, Department of Clinical and Experimental Medicine, Pisa, Italy
  • 6Department of Medical Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
  • 7Department of Oncology, University and General Hospital, Udine, Italy
  • 8Department of Oncology, General Hospital San Bortolo, Unità Locale Socio-Sanitaria 8 Berica, Vicenza, Italy
  • 9Department of Medical Oncology, Infermi Hospital, Rimini, Italy
  • 10Medical Oncology Unit, Università Cattolica del Sacro Cuore, Rome, Italy
  • 11Medical Oncology Unit, University Hospital, Parma, Italy
  • 12Medical Oncology Unit, Fatebenefratelli–Isola Tiberina Hospital, Rome, Italy
  • 13Medical Oncology Unit, Presidio Ospedaliero Felice Lotti, Pontedera, Italy
JAMA Oncol. Published online November 21, 2018. doi:10.1001/jamaoncol.2018.5080
Key Points

Question  Is third-line cetuximab plus irinotecan an active option for patients with RAS and BRAF wild-type metastatic colorectal cancer who have acquired resistance to first-line irinotecan- and cetuximab-based therapy?

Findings  In this phase 2 single-arm clinical trial, rechallenge with cetuximab plus irinotecan was active in 21% of patients with RAS and BRAF wild-type metastatic colorectal cancer. Preplanned circulating tumor DNA profiling revealed that only patients with RAS and BRAF wild-type circulating tumor DNA at the time of rechallenge could derive benefit.

Meaning  These findings lay the foundation for further evaluating the efficacy of anti–epidermal growth factor receptor rechallenge in larger studies including only patients with no mechanisms of acquired resistance detectable in circulating tumor DNA.

Abstract

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  ClinicalTrials.gov Identifier: NCT02296203

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