Prognostic Relevance of ctDNA RAS Mutation in Patients With Metastatic Colorectal Cancer Treated With Cetuximab

Area of Science:

• Oncology
• Molecular Diagnostics
• Cancer Genomics

Background:

• RAS mutations are key biomarkers for anti-EGFR therapy efficacy in metastatic colorectal cancer (mCRC).
• RAS mutation emergence is a known mechanism of resistance to anti-EGFR treatments.
• Understanding the temporal dynamics of RAS mutations is crucial for predicting treatment outcomes.

Purpose of the Study:

• To evaluate the prognostic significance of circulating tumor DNA (ctDNA) RAS mutations in mCRC patients receiving first-line cetuximab.
• To investigate the temporal dynamics of RAS mutation emergence during cetuximab-based therapy.
• To assess the impact of emergent ctDNA RAS mutations on progression-free survival (PFS).

Main Methods:

• Prospective study of mCRC patients with tissue-confirmed RAS wild-type status.
• Serial ctDNA sampling at baseline, every 8 weeks, and post-treatment.
• First-line treatment with cetuximab combined with FOLFOX or FOLFIRI.
• Analysis of emergent ctDNA RAS mutations and their association with PFS.

Main Results:

• High concordance (89.1%) between baseline ctDNA and tissue RAS status.
• Over 50% of RAS wild-type cases developed emergent RAS mutations in ctDNA.
• While single transient mutations were not consistently linked to poor PFS, any detection of ctDNA RAS mutations significantly correlated with reduced PFS (aHR=2.24, P=.02).

Conclusions:

• Emergence of ctDNA RAS mutations during cetuximab therapy shows temporal variability.
• The presence of ctDNA RAS mutations at any time point during treatment is a significant indicator of poorer PFS in mCRC patients.
• Monitoring ctDNA RAS mutations offers prognostic value in guiding anti-EGFR therapy decisions.