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?
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.
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.
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).
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.
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.
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.
ClinicalTrials.gov Identifier: NCT02296203
Cremolini C, Rossini D, Dell’Aquila E, et al. 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. JAMA Oncol. Published online November 21, 2018. doi:10.1001/jamaoncol.2018.5080
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