Deletion — oncology-focused definition
A chromosomal deletion is a structural genetic abnormality in which a segment of a chromosome is lost, resulting in loss of genetic material.
Oncology relevance:
- Often leads to loss of tumor suppressor genes, contributing to malignant transformation.
- Considered a loss-of-function event and usually requires loss of both alleles for full effect (two-hit hypothesis).
Clinical significance (for oncology pharmacists):
- Used for diagnosis, prognosis, and risk stratification, especially in hematologic malignancies.
- Can influence treatment intensity and monitoring strategies.
- Detected by karyotyping, FISH, array CGH, or NGS.
Common examples:
- del(5q) → myelodysplastic syndrome (often favorable prognosis; lenalidomide-sensitive)
- del(17p) → loss of TP53 (poor prognosis in CLL, MM)
- del(13q) → CLL, multiple myeloma
Key takeaway:
Chromosomal deletions promote cancer by removing tumor suppressor genes, making them critical markers for prognosis and therapeutic decision-making in oncology.
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