Learning Objective

By the end of this section, learners should be able to explain the principles and clinical applications of liquid biopsy, including its role in cancer profiling, treatment monitoring, and post-treatment surveillance.

A liquid biopsy is a noninvasive diagnostic test performed on body fluids (e.g., blood, urine) that detects:

• Circulating tumor DNA (ctDNA)
• Circulating tumor RNA (ctRNA)
• Circulating tumor cells (CTCs)

Clinical Applications

1. Cancer profiling – Detects actionable mutations, e.g., EGFR mutations in lung cancer.
2. Treatment monitoring – Tracks response to therapy in real time.
3. Post-treatment surveillance – Detects minimal residual disease or early recurrence (e.g., in colorectal cancer).
4. Early metastatic detection – Identifies metastases before clinical symptoms appear.
5. Personalized therapy – Guides targeted treatments based on tumor genetic profile.

High-Yield Step 1 Points

• Provides a minimally invasive alternative to tissue biopsy.
• Can be repeated multiple times for dynamic monitoring.
• Particularly useful in cancers where tumor tissue is difficult to access.

Activity