Download Risk Estimates, 6 Examples and Solutions

RISK ESTIMATES: SIX EXAMPLES WITH SOLUTIONS
RELATIVE RISK:
WHAT IS THE RELATIVE RISK GIVEN THE INCIDENCE OF 5 RADIATION‐INDUCED CANCER CASES FROM AMONG A POPULATION OF 6,500 WHEN THE EXPECTED INCIDENCE OF NON‐
RADIATION‐INDUCED CANCER IS 38 PER 100,000?
RELATIVE RISK: SOLUTION
 The expected incidence is 38/100,000 = 0.00038
 Applied to a population of 6,500, the expected cases = 6,500 x 0.00038 = 2.47 cases.
 The observed cases = 5 cases
 Relative Risk = Observed Cases/ Expected Cases = 5 /2.47 = 2.02 Cases (over 102%).
EXCESS RISK:
WHAT IS THE EXCESS RISK GIVEN THE INCIDENCE OF 5 RADIATION‐INDUCED CANCER CASES FROM AMONG A POPULATION OF 6,500 WHEN THE EXPECTED INCIDENCE OF NON‐
RADIATION‐INDUCED CANCER IS 38 PER 100,000?
EXCESS RISK: SOLUTION
 The expected incidence is 38/100,000 = 0.00038
 Applied to a population of 6,500, the expected cases = 6,500 x 0.00038 = 2.47 cases.
 The observed cases = 5 cases
 Excess Risk = Observed Cases – Expected Cases = 5 – 2.47 = 2.53 Cases
ABSOLUTE RISK:
Based on the best statistical estimates, the absolute risk for radiation‐induced lung cancer is 20 cases/million/rad/year for a 10‐year at risk period. If 100,000 people receive 2,400 mrad during chest CT, what total number of cancer cases that could result?
ABSOLUTE RISK: SOLUTION
 Expected cancer deaths = 20/106/rad/year = 0.00002
 Applied to a population of 100,000, the expected cases = 100,000x 0.00002 = 2.0 cases
 Absolute Risk = Expected Cases x dose in RAD/year = 2.0 x 2.4 = 4.8 Cases over a 10‐
year period.
RELATIVE RISK:
What is the relative risk given the incidence of 4 radiation‐induced cancer cases from among a population of 12,600 when the number of spontaneous cancer cases is 35 per 100,000 population?
RELATIVE RISK: SOLUTION
EXCESS RISK
A sample of 2,500 radiologists revealed that 15 had skin cancer. The natural incidence of skin cancer in the population is 1.25 per 100,000. How many excess cancers were found among the radiologists sampled?
EXCESS RISK: SOLUTION
ABSOLUTE RISK
The absolute risk for radiation‐induced bone cancer is considered to be 12 cases per million/rad/year for a 10‐year at‐risk period. If 100,000 people receive 1,250 mrem during bone survey radiography, what total number of cancers would be expected to be induced during the same at‐risk period?
ABSOLUTE RISK: SOLUTION