Table 4.

Multivariable Cox proportional hazard regression analyses for subsequent breast cancer in female 5-year childhood cancer survivors whose treatment history did not include chest radiotherapy nor alkylating agent chemotherapy (primary cancer diagnosis year 1946–2012)^a

	Total (n)	%	No. of SBC (n)	%	HRb	95% CI
Cumulative doxorubicin dose (mg m−²)
0	5,880	90.5	61	71.8	1.0	Ref.
<300c	305	4.7	7	8.2	2.35	0.96–5.71
300–399	131	2.0	5	5.9	2.67	1.08–6.59
≥400	136	2.1	8	9.4	3.58	1.66–7.71
Unknown	47	0.7	4	4.7	–	–
Daunorubicin
No	6,020	92.6	81	95.3	1.0	Ref.
Yes	479	7.4	4	4.7	1.43	0.48–4.24
Epirubicin
No	6,362	97.9	84	98.8	1.0	Ref.
Yes	137	2.1	1	1.2	3.46	0.41–29.10

^aIn total, 6,499 female 5-year survivors did not receive chest radiotherapy nor alkylating agent chemotherapy, among whom 85 developed SBC during follow-up.

^bModels were further adjusted for pelvic radiotherapy ≥5 Gy (yes/no) and age at primary childhood cancer diagnosis (categorical variable).

^cThe cumulative doxorubicin dose (mg m⁻²) categories <100 (0 case/46 survivors), 100–199 (1 case/129 survivors) and 200–299 (6 cases/130 survivors) were collapsed due to low numbers of SBC cases.