Table 6:
Risk of secondary leukemia according to the dose of alkylating agents or topoisomerase II inhibitors and radiotherapy (RT)
| Treatment characteristics | Cases/controls | Reference: No RT, no studied drug category | Reference: RT, no studied drug category |
|---|---|---|---|
| Odds ratio$ (95% CI) | Odds ratio$ (95% CI) | ||
| All leukemias | 147/522 | ||
| Alkylating agents | |||
| No RT and 0 mg/m2 | 13/102 | 1.0 (Reference) | 0.6 (0.27-1.3) |
| No RT and >0-22000 | 30/113 | 0.9 (0.38-2.1) | 0.5 (0.26-1.1) |
| No RT and >22000 | 7/9 | 2.2 (0.54-9.1) | 1.3 (0.37-4.7) |
| RT and 0 mg/m2 | 35/144 | 1.7 (0.76-3.7) | 1.0 (Reference) |
| RT and >0-22000 | 36/130 | 1.0 (0.44-2.5) | 0.6 (0.32-1.2) |
| RT and >22000 | 26/24 | 4.8 (1.6-14.6) | 2.9 (1.1-7.2) |
| §P-value for interaction | 0.1 | 0.1 | |
| Topoisomerase II inhibitors | |||
| No RT and 0 mg/m2 | 12/113 | 1.0 (Reference) | 0.6 (0.26-1.3) |
| No RT and >0-2500 | 27/99 | 4.1 (1.7-10.2) | 2.4 (1.0-5.5) |
| No RT and >2500 | 11/12 | 12.5 (3.4-45.6) | 7.1 (2.1-24.6) |
| RT and 0 mg/m2 | 38/182 | 1.8 (0.79-3.9) | 1.0 (Reference) |
| RT and >0-2500 | 38/97 | 5.2 (2.2-12.3) | 3.0 (1.4-6.4) |
| RT and >2500 | 21/19 | 16.1 (5.0-51.4) | 9.2 (3.0-28.1) |
| §P-value for interaction | 0.8 | 0.8 | |
| AML | 101/356 | ||
| Alkylating agents | |||
| No RT and 0 mg/m2 | 9/68 | 1.0 (Reference) | 0.5 (0.19-1.3) |
| No RT and >0-22000 | 17/72 | 0.8 (0.30-2.4) | 0.4 (0.18-1) |
| No RT and >22000 | 5/4 | 5.7 (0.91-36.1) | 2.8 (0.55-14.6) |
| RT and 0 mg/m2 | 27/104 | 2.0 (0.77-5.4) | 1.0 (Reference) |
| RT and >0-20000 | 23/89 | 1.3 (0.45-3.7) | 0.6 (0.29-1.4) |
| RT and >20000 | 20/19 | 6.2 (1.5-25.4) | 3.1 (0.96-9.8) |
| §P-value for interaction | 0. 2 | 0. 2 | |
| Topoisomerase II inhibitors | |||
| No RT and 0 mg/m2 | 9/72 | 1.0 (Reference) | 0.6 (0.23-1.7) |
| No RT and >0-2500 | 15/64 | 2.6 (0.89-7.7) | 1.6 (0.57-4.7) |
| No RT and >2500 | 7/8 | 14.3 (2.7-75.1) | 9.0 (1.8-43.9) |
| RT and 0 mg/m2 | 26/135 | 1.6 (0.60-4.3) | 1.0 (Reference) |
| RT and >0-2500 | 30/65 | 6.1 (2.2-16.9) | 3.8 (1.5-9.5) |
| RT and >2500 | 14/12 | 10.2 (2.5-42) | 6.4 (1.6-25.5) |
| §P-value for interaction | 0.2 | 0.2 | |
Abbreviations: 95% CI = 95% confidence interval; RT = radiotherapy; AML= Acute myeloid leukemia.
Conditional logistic regression matched on gender, age at childhood cancer diagnosis and follow-up, and adjusted for all the other drugs (platinum compounds and topoisomerase II inhibitors or alkylating agents) and year of diagnosis. The categories of doses of alkylating agents or topoisomerase II inhibitors were defined by the percentile (66%) of the distribution in the cases group.
P-value for interaction between radiotherapy and Alkylating agents or Topoisomerase II inhibitors was calculated using a likelihood ratio test under the multiplicative model.