Table 5.
Outcomes for the exposed group by type of cancer and years since first CT exposure, based on a one year lag period
| Type of cancer | No of years since first exposure | P for trend | |||
|---|---|---|---|---|---|
| 1-4 | 5-9 | 10-14 | ≥15 | ||
| Observed no of cancers in exposed group, IRR (95% CI)* | |||||
| Brain cancer | 121, 2.82 (2.34 to 3.39) | 83, 2.03 (1.62 to 2.54) | 46, 1.50 (1.11 to 2.01) | 33, 1.67 (1.18 to 2.36) | <0.001 |
| After brain CT | 87, 3.24 (2.61 to 4.02) | 62, 2.42 (1.88 to 3.12) | 36, 1.80 (1.29 to 2.51) | 25, 1.74 (1.17 to 2.59) | <0.001 |
| After other CT | 34, 2.08 (1.47 to 2.92) | 21, 1.34 (0.87 to 2.07) | 10, 0.93 (0.50 to 1.73) | 8, 1.47 (0.73 to 2.94) | 0.06 |
| All solid cancers except brain cancer | 438, 1.23 (1.12 to 1.35) | 646, 1.17 (1.09 to 1.27) | 611, 1.14 (1.05 to 1.24) | 529, 1.24 (1.14 to 1.35) | 0.88 |
| Leukaemias and myelodysplasias | 95, 1.20 (0.98 to 1.48) | 85, 1.40 (1.13 to 1.74) | 39, 1.07 (0.78 to 1.47) | 27, 1.19 (0.81 to 1.75) | 0.82 |
| Other lymphoid and haematopoietic cancers | 131, 1.25 (1.05 to 1.49) | 146, 1.27 (1.08 to 1.50) | 76, 1.00 (0.79 to 1.25) | 44, 1.02 (0.76 to 1.38) | 0.44 |
| All cancers | 785, 1.35 (1.25 to 1.45) | 960, 1.25 (1.17 to 1.34) | 772, 1.14 (1.06 to 1.22) | 633, 1.24 (1.14 to 1.34) | 0.009 |
| All solid cancers, except brain cancer after brain CT | 472, 1.26 (1.16 to 1.38) | 667, 1.18 (1.09 to 1.27) | 621, 1.14 (1.05 to 1.23) | 537, 1.24 (1.14 to 1.36) | 0.72 |
| All cancers, except brain cancer after brain CT | 698, 1.25 (1.16 to 1.35) | 898, 1.21 (1.13 to 1.29) | 736, 1.12 (1.04 to 1.20) | 608, 1.22 (1.13 to 1.32) | 0.30 |
| No of excess cancers in exposed group, EIR per 100 000 person years (95% CI)* | |||||
| Brain cancer | 77.6, 3.09 (2.23 to 3.94) | 41.4, 1.91 (1.09 to 2.74) | 15.1, 1.25 (0.15 to 2.34) | 13.2, 2.21 (0.32 to 4.10) | 0.03 |
| After brain CT | 60.1, 3.97 (2.76 to 5.18) | 36.1, 2.66 (1.52 to 3.79) | 15.9, 1.95 (0.51 to 3.38) | 10.6, 2.40 (0.19 to 4.60) | 0.05 |
| After other CT | 17.6, 1.75 (0.61 to 2.89) | 5.3, 0.66 (−0.46 to 1.78) | −0.8, −0.20 (−1.77 to 1.37) | 2.5, 1.67 (−1.98 to 5.32) | 0.11 |
| All solid cancers except brain cancer | 81.2, 3.23 (1.60 to 4.86) | 95.3, 4.40 (2.10 to 6.71) | 76.3, 6.29 (2.30 to 10.29) | 103.0, 17.29 (9.72 to 24.86) | 0.01 |
| Leukaemias and myelodysplasias | 16.4, 0.65 (−0.11 to 1.41) | 24.5, 1.13 (0.30 to 1.97) | 2.6, 0.21 (−0.80 to 1.22) | 4.3, 0.73 (−0.98 to 2.44) | 0.78 |
| Other lymphoid and haematopoietic cancers | 25.9, 1.03 (0.14 to 1.92) | 31.2, 1.44 (0.35 to 2.54) | −0.5, −0.04 (−1.45 to 1.37) | 0.8, 0.14 (−2.05 to 2.32) | 0.54 |
| All cancers | 201.2, 8.00 (5.81 to 10.18) | 192.4, 8.90 (6.09 to 11.70) | 93.6, 7.71 (3.22 to 12.20) | 121.3, 20.36 (12.09 to 28.64) | 0.43 |
| All solid cancers, except brain cancer after brain CT | 98.8, 3.93 (2.09 to 5.77) | 100.5, 4.65 (2.20 to 7.10) | 75.5, 6.23 (2.09 to 10.37) | 105.5, 17.72 (9.92 to 25.52) | 0.01 |
| All cancers, except brain cancer after brain CT | 141.1, 5.61 (3.43 to 7.79) | 156.3, 7.23 (4.42 to 10.03) | 77.6, 6.40 (1.91 to 10.89) | 110.7, 18.58 (10.30 to 26.86) | 0.04 |
IRR=incidence rate ratio, exposed v unexposed; EIR=absolute excess incidence rate compared with rates in unexposed group.
*IRR, EIR, and number of excess cancers calculated after stratification for age, sex, and year of birth.