. 2019 Mar 1;103(3):595–604. doi: 10.1016/j.ijrobp.2018.10.025

Table 2.

Associations between treatment characteristics and rate of myocardial infarction

Total	Cases		Controls		Rate ratio^∗	95% CI	P^†
Total	183 (N)	100 (%)^‡	182 (N)	100 (%)^‡	Rate ratio^∗	95% CI	P^†
Treatment model
Surgery
Breast conserving surgery (BCS)	82	44.8	87	47.8	1.00^§	-
Mastectomy	101	55.2	95	52.2	1.04	0.58-1.86	.90
Endocrine therapy
No	167	91.3	166	91.2	1.00^§	-
Yes	16	8.7	16	8.8	0.71	0.29-1.75	.46
Chemotherapy (CT)
No	140	76.5	132	72.5	1.00^§	0.89-1.12
CT, no anthracyclines	29	15.9	36	19.8	0.59	0.33-1.07
Anthracycline-based CT	14	7.7	14	7.7	1.04	0.41-2.63	.23
Radiation therapy (RT)
No	16	8.7	27	14.8	1.00^‡	0.50-1.99
RT, no IMC	51	27.9	65	35.7	1.20	0.67-2.18
RT, IMC	116	63.4	90	49.5	2.45	1.97-3.05	.006
Mean whole heart dose (MWHD)^‖
Median MWHD (IQR) in Gy	8.9	4.8-15.0	8.5	4.3-12.2
No RT	16	8.8	27	15.0	1.00^§	0.52-1.91
<2 Gy (mean 1 Gy)	29	15.9	34	18.9	1.44	0.84-2.48
2-9 Gy (mean 7 Gy)	62	34.1	62	34.4	1.72	1.23-2.42
10-19 Gy (mean 14 Gy)	57	31.3	48	26.7	2.06	1.40-3.02
≥20 Gy (mean 26 Gy)	18	9.9	9	5.0	3.42	1.54-7.62	.011^¶

Abbreviations: CI = confidence interval; IMC = internal mammary chain; IQR = interquartile range; MI = myocardial infarction.

^∗

Univariable rate ratios for MI for different levels of each factor were calculated using logistic regression conditioning on strata defined by the matching variables.

^†

P value for difference between treatment characteristics of cases and controls, calculated within strata (defined by matching variables).

^‡

Percentages may not total 100 because of rounding.

^§

Reference category.

^‖

This model includes 362 patients. Three patients were dropped; for one irradiated case and one irradiated control, dosimetry was not performed. One control was dropped because it was the only patient left in the stratum.

^¶

P for trend across categories.