61. Targeted therapy - general characteristics. Targeted therapy for colorectal carcinomas and gastrointestinal stromal tumors (GIST).
Covers the general features of targeted therapy, its molecular targets and drug classes, then applies these to colorectal carcinoma (EGFR, RAS status, BRAF V600E and anti-VEGF agents) and to gastrointestinal stromal tumours (KIT and PDGFRA mutations and tyrosine kinase inhibitors). Also includes a comparison table of the two diseases, a list of resistance limitations, and the role of molecular testing.
Topic 61 of 65 in the MU Sofia syllabus for Genetics (Medicine, Year 3). The free AceMed note covers it in 10 sections, about 559 words (4 min of reading), with 15 flashcards.
In this note
Targeted therapy - general characteristics. Targeted therapy for colorectal carcinomas and gastrointestinal stromal tumors (GIST).
I. GENERAL CHARACTERISTICS OF TARGETED THERAPY
II. MOLECULAR BASIS OF TARGETED THERAPY
Main Classes of Targeted Drugs
III. TARGETED THERAPY IN COLORECTAL CARCINOMA (CRC)
IV. TARGETED THERAPY IN GASTROINTESTINAL STROMAL TUMORS (GIST)
V. TYROSINE KINASE INHIBITORS IN GIST
VI. COMPARISON: CRC vs GIST TARGETED THERAPY
VII. LIMITATIONS OF TARGETED THERAPY
VIII. ROLE OF MOLECULAR DIAGNOSTICS
I. GENERAL CHARACTERISTICS OF TARGETED THERAPY
Targeted therapy is a form of cancer treatment that specifically interferes with molecular targets involved in:
tumor growth,
cell proliferation,
survival,
angiogenesis,
metastatic potential.
Unlike conventional chemotherapy, targeted therapy acts on defined molecular abnormalities rather than all rapidly dividing cells.
Key Concept
Targeted therapy requires molecular characterization of the tumor, because drug effectiveness depends on the presence or absence of specific genetic alterations.
Difference from Conventional Chemotherapy
Chemotherapy → non-specific cytotoxicity
Targeted therapy → molecular selectivity
As a result, targeted therapy often shows:
higher specificity,
lower systemic toxicity,
variable response depending on tumor genetics.
II. MOLECULAR BASIS OF TARGETED THERAPY
Main Molecular Targets
Targeted therapies act against:
mutated or overexpressed receptors,
constitutively activated kinases,
dysregulated signaling pathways,
angiogenic factors.
Mechanisms of Action
1. Block receptor–ligand interaction.
2. Inhibit intracellular tyrosine kinases.
3. Interrupt oncogenic signaling cascades.
4. Inhibit tumor angiogenesis.
5. Induce apoptosis or cell cycle arrest.
Main Classes of Targeted Drugs
1. Monoclonal Antibodies
Act on cell surface receptors or ligands
Usually administered intravenously
2. Small-Molecule Inhibitors
Enter cells
Inhibit intracellular enzymes (mainly kinases)
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