L2.2 How cancer kills

• Cancers can impair or alter the normal functioning of organs
• Lung cancers

  • Tumour reduces gas exchange, either directly, or through haemorrhage
• Leukaemia

  • Fewer red blood cells due to perturbed haemopoiesis → anaemia
• Mouth, oesophagus, stomach, intestinal, pancreas, thyroid & liver cancers

  • Eating difficult/painful, impaired uptake of nutrients, reduction in metabolic hormones and digestive factors
• Solid tumours


  • Vessel rupture due to tumour growth

  
• Leukaemia

  • Platelet loss → clotting defects
• Liver cancer


  • Decrease in synthesis of clotting factors
• Leukaemia


  • Cells crowd blood & bone marrow so fewer functional immune cells
• Gastrointestinal cancers


  • Can perforate intestinal wall, may enable access to bloodstream or organs by food microbes
• Brain tumours


  • Compression effects (even from benign tumours)
  • Disruption of neurological networks due to invasion of cancer cells

  
• Metastases cause most cancers deaths
• Metastatic cancer cells


  • Have overcome strong selective pressures: numerous checks on cancerous behavior
  • More invasive, more self-sufficient, less prone to immune targeting, less sensitive to chemotherapy
  • Common sites of metastases are essential organs: lungs, liver, brain

  
• 5 year survival rates: 8%, 44-74%, 78%, 93%, 100%
• Cachexia


  • Characterised by wasting: fat and skeletal muscle breakdown
  • Associated with appetite suppression
  • Pro-inflammatory cytokines promote catabolism
• Cachexia affects 50% of cancer patients