Lesson 2 Population Screening, how cancer kills

• CRICOS Provider 00115M
• MED3ATA Cancer Module

  
• Christine Hawkins
• Lecture 2.1: Population screening
• La Trobe University
• Commonwealth of Australia
• Copyright Act 1968
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• Throughout these cancer lectures: Brown text is examinable, Grey text is just for your interest: not examinable
• Requirements for a population screening program

  • Most cancers are identified after a person experiences symptoms, but some are detected through population-based screening of healthy people
  • Screening programs must provide more benefit than harm to the people being screened

  
• Australian Institute of Health and Welfare 2018. Analysis of cancer outcomes and screening behaviour for national cancer screening programs in Australia. Cancer series no. 111. Cat. no. CAN 115. Canberra: AIHW

  
• Current Australian population-based cancer screening programs

  • Mammogram (x-ray) detects unusually dense parts of breast (possible tumour)
  • 99% of cervical cancer cases are caused by infection with Human Papilloma Viruses. Previously, "Pap" smears → histological screening, Now, HPV infection assayed by PCR
  • Often very small amounts of blood leak from small growths in bowel, Screen detects this blood in stool samples

  
• Targeted age range 50-74, Screening every two years
• Relative risk

  Proportion of screened people who got cancer / Proportion of unscreened people who got cancer

  
• Relative risk of 1: the risk of getting cancer was equivalent in the two groups, Relative risk of 0.5: means screened people were half as likely to get cancer as unscreened people, 95% confidence interval: the likely range within which the true hazard ratio lies

  
• Lung cancer screening? Coming in 2025.

  
• Prostate cancer screening? Not until a better test is developed

  
• Skin cancer screening? No. Current methods would not reduce illness or death from skin cancer

  
• Breast cancer screening controversy: Fewer young women get breast cancer, Tumours are more difficult to detect by mammograms in younger (denser) breasts, Benefit of breast cancer screening increases with age, Most countries offer screening to women aged 50+, Report recommended US government start screening at 50, Breast cancer activists, radiographer groups protested, Lobbying worked: US still requires insurance companies to cover mammograms for women aged 40-50

  
• Berry, D. Breast 22: S73–S76, 2013
• Number needed to invite to screening to save one life