Tumor Heterogeneity and Lesion-Specific Response to Targeted Therapy in Colorectal Cancer

Area of Science:

• Oncology
• Genetics
• Molecular Biology

Background:

• Acquired resistance to targeted therapies is a significant challenge in cancer treatment.
• Understanding genomic heterogeneity is key to overcoming resistance.
• EGFR blockade in colorectal cancer provides a model to study resistance mechanisms.

Purpose of the Study:

• To investigate how genomic heterogeneity affects response to subsequent therapies after acquired resistance.
• To assess the integration of tissue and liquid biopsies with imaging for monitoring oncogenic alterations and lesion-specific responses.
• To identify novel resistance mechanisms and their impact on treatment efficacy.

Main Methods:

• Studied EGFR blockade in colorectal cancer.
• Integrated tissue biopsies, liquid biopsies (ctDNA), and radiologic imaging.
• Analyzed MEK1 and KRAS mutations in progressing metastases.
• Monitored treatment response to panitumumab and trametinib.

Main Results:

• Identified a novel MEK1(K57T) mutation as a mechanism of acquired resistance, with the lesion regressing upon combination therapy.
• Detected a new KRAS(Q61H) mutation in ctDNA that increased despite therapy and was found in a separate nonresponding metastasis.
• Demonstrated that distinct resistance mechanisms in separate lesions drive lesion-specific responses to subsequent targeted therapies.

Conclusions:

• Molecular heterogeneity from acquired resistance drives lesion-specific responses to targeted therapies.
• Single-lesion biopsy analysis is insufficient for guiding subsequent targeted therapy selection.
• ctDNA profiling detects concomitant resistance mechanisms in separate metastases and assesses therapy effectiveness.