Table 5:

Risk of secondary leukemia according to the age weighted average radiation dose to active bone marrow (ABM) and to chemotherapy (CT)

Treatment characteristics	Cases/controls	Reference: No CT, no RT	Reference: CT, no RT
		Odds ratio$ (95% CI)	Odds ratio$ (95% CI)
All leukemias	147/522
No CT and 0 Gy*	2/69	1.0 (Reference)	0.0 (0.01-0.3)
No CT and >0-12	11/66	7.7 (1.7-36.2)	0.4 (0.16-1.0)
No CT and >12	2/16	3.7 (0.28-49.9)	0.2 (0.02-1.7)
CT and 0 Gy	49/161	18.8 (3.9-92)	1.0 (Reference)
CT and >0-12	61/171	22.3 (4.6-108)	1.2 (0.75-1.9)
CT and >12	22/39	33.0 (6.3-173.9)	1.8 (0.85-3.6)
§P-value for interaction		0.01	0.01
AML	101/356
No CT and 0 Gy*	2/41	1.0 (Reference)	0.1 (0.02-0.6)
No CT and >0-12	7/45	4.9 (0.95-25.6)	0.6 (0.20-1.6)
No CT and >12	1/12	-	-
CT and 0 Gy	30/107	8.6 (1.7-44)	1.0 (Reference)
CT and >0-12	43/120	11.8 (2.3-59.8)	1.4 (0.77-2.4)
CT and >12	18/31	18.8 (3.3-105.7)	2.2 (0.94-5.0)
§P-value for interaction		0.03	0.03

Abbreviations: 95% CI = 95% confidence interval; CT = chemotherapy; RT = radiotherapy; AML= Acute myeloid leukemia.

^$Conditional logistic regression matched on gender, age at childhood cancer diagnosis and follow-up and adjusted for year of diagnosis.

^*The classes of whole active bone marrow radiation dose (Gy) were grouped as 0, >0-12 (highest quartile) and >12 Gy for the analysis in table 3.

^§P-value for interaction between chemotherapy and active bone marrow radiation dose was calculated using a likelihood ratio test under the multiplicative model.