Table 3 Smallest measurable SIRs for cancer and leukaemia for different scenarios (adapted from:[36])

Cohort size

8,000

25,000

32,000

Follow-up duration (years)

15

15

15

Person-years

120,000

375,000

480,000

Expected number of childhood cancer cases in the cohort^a

16

51

65

Smallest measurable SIR (all cancers)^b

1.7

1.4

1.3

Expected number of childhood leukaemia cases in the cohort^a

5.6

17.6

22.6

Smallest measurable SIR (all leukaemia)^b

2.1

1.6

1.5