Precision medicine uses patients’ genomic information, molecular profiles, and individual factors to guide personalized prevention and treatment — rather than applying uniform standard protocols. Since the Human Genome Project completed in 2003, sequencing costs have fallen from $3 billion to under $1,000 per whole-genome sequence, making large-scale clinical precision medicine feasible.
## Oncology Precision Medicine: The Most Mature Application
**Companion diagnostics (CDx)**: genomic testing identifies whether a patient carries the relevant mutation before prescribing a targeted therapy. Only mutation-positive patients receive the targeted drug. Key examples: BRCA1/2 mutation → PARP inhibitors (olaparib); EGFR mutation → EGFR inhibitors (osimertinib); HER2 amplification → trastuzumab (Herceptin).
**NGS panel tumor profiling**: next-generation sequencing of tumor tissue tests hundreds of cancer-associated genes in a single run, guiding selection of targeted or immunotherapy. Foundation One CDx (dual FDA and NMPA approval), BGI Genomics, and Burning Rock’s NGS panels are representative products.
**MSI-H/TMB-H pan-tumor biomarkers**: high microsatellite instability (MSI-H) and high tumor mutational burden (TMB-H) predict immunotherapy response (PD-1/PD-L1 inhibitors) independently of primary tumor site — representing precision medicine’s shift from “tissue of origin” to “molecular subtype” as the treatment determinant.
## Liquid Biopsy
Liquid biopsy analyzes circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), or other tumor-derived molecular markers from blood samples, achieving non-invasive tumor detection.
**Early cancer screening**: GRAIL’s Galleri test claims to detect signals from 50+ cancers from ctDNA methylation patterns. The NHS pilot (140,000 participants) is evaluating clinical utility; results expected 2026.
**Treatment monitoring**: ctDNA dynamics reflect tumor treatment response earlier than conventional imaging, enabling earlier detection of recurrence and resistance.
**Minimal residual disease (MRD)**: post-surgery or post-chemotherapy ctDNA testing detects residual cancer, guiding adjuvant treatment decisions.
See [CRISPR Gene Editing](https://sunqi.org/crispr-gene-editing-advances-en/), [AI Drug Discovery](https://sunqi.org/drug-discovery-ai-pipeline-en/), and the [NIH Precision Medicine Initiative](https://www.nih.gov/precision-medicine-initiative).
