5.Age & Cancer

1. Cancer Frequency and Aging

Peak cancer incidence

• Cancer frequency increases with age.
• Highest risk between 55–75 years → “cancer danger decades.”

Decline after 75 years

• Incidence curve decreases after ~75.
• Not because risk falls → rather because fewer individuals survive to that age → shrinking denominator effect.

Biological explanations for rise with age

• Somatic mutations accumulate over decades

(DNA damage builds like gradual “rust”).

• Immune system declines with age

(immunosenescence → weaker tumor surveillance).

Concept summary:

Mutations + immune decline = higher cancer probability in elderly.

2. Cancer in Children (<15 years)

• Cancer is not only a disease of old age.
• In children, cancer accounts for ~10% of all deaths.
• Significant because injuries + infections dominate this age group.

3. Most Common Childhood Cancers

Childhood cancers differ from adult patterns.

Most fatal types include:

• Leukemias
• CNS tumors (brain + spinal cord)
• Lymphomas
• Soft-tissue sarcomas
• Bone sarcomas

4. Key Scientific Insight from Childhood Tumors

• Study of retinoblastoma led to discovery of:
• tumor suppressor genes
• specifically the RB gene, central to cell-cycle control.
• Importance:
• Demonstrated how loss of tumor suppressor function drives malignant transformation.
• Foundational model for hereditary vs sporadic cancer genetics.

5. Core Facts to Memorize

Mnemonic aids

• “Cancer danger decades” → 55–75 yrs
• “Rust + sleepy guard” → DNA mutations + immune decline
• “Little L’s for little lives” → Leukemia, Lymphoma, CNS, Sarcoma
• “RB opened our eyes” → retinoblastoma + tumor suppressor gene

Take-home messages

• Cancer risk peaks in later adulthood due to accumulated mutations + weakened immune surveillance.
• Cancer in children, though less common, remains a major cause of death.
• Childhood tumor research (retinoblastoma) shaped modern cancer genetics.