Head-to-head comparison of perfluorobutane contrast-enhanced US and multiparametric MRI for breast cancer: a prospective, multicenter study

Table 1 Baseline characteristics of the study patients

Characteristic	Overall lesions (n = 186)	Development cohort (n = 151)	Validation cohort (n = 35)
Age (years)^b	49 ± 11 (19, 76)	49 ± 11 (19, 76)	49 ± 10 (27, 68)
Age (years)^b
< 49	90 (48.4)	76 (50.3)	14 (40.0)
≧ 49	96 (51.6)	75 (49.7)	21 (60.0)
Body mass index (kg/m²)^b	23.9 ± 3.5 (13.7, 37.0)	23.9 ± 3.3 (16.4, 37.0)	23.5 ± 4.2 (13.7, 34.1)
Body mass index (kg/m²)
< 18.5	6 (3.4)	3 (2.1)	3 (9.1)
18.5 to < 25	110 (61.5)	91 (62.3)	19 (57.6)
≥ 25.0	63 (35.2)	52 (35.6)	11 (33.3)
Dense breast^e
Yes	137 (76.5)	107 (73.3)	30 (90.9)
No	42 (23.5)	39 (26.7)	3 (9.1)
Parity status
Nulliparous	16 (8.9)	14 (9.6)	2 (6.1)
Parous	163 (91.1)	132 (90.4)	31 (93.9)
Menopausal status^c
Premenopausal	107 (59.8)	89 (61.0)	18 (54.5)
Postmenopausal	72 (40.2)	57 (39.0)	15 (45.5)
First-degree relatives with breast cancer^d
Presence	169 (94.4)	138 (94.5)	31 (93.9)
Absence	10 (5.6)	8 (5.5)	2 (6.1)
Diagnosis method
Surgery	73 (39.2)	62 (41.1)	11 (31.4)
Core biopsy	113 (60.8)	89 (58.9)	24 (68.6)
Lesion size (cm)^a	1.8 (1.2, 2.4)	1.8 (1.2, 2.5)	1.8 (1.3, 2.4)
Lesion size (cm)^a
< 1.5	65 (34.9)	52 (34.4)	13 (37.1)
≧ 1.5	121 (65.1)	99 (65.6)	22 (62.9)
Histologic type
Benign	71 (38.1)	58 (38.4)	13 (37.1)
Malignant	115 (61.8)	93 (61.6)	22 (62.9)

Unless otherwise indicated, data are numbers of patients, and data in parentheses are percentages
^aData are medians, and data in parentheses are the interquartile range
^bData are means ± standard deviations, and data in parentheses are the range
^cMenopausal status: Women aged 60 years or older, reporting a history of hysterectomy, or reporting no periods within the past 12 months without the use of hormonal contraceptives were categorized as postmenopausal. Women reporting regular periods (12–18 times in the last 12 months) without the use of hormonal contraceptives were categorized as premenopausal
^dFirst-degree relatives (mother, sister, and daughter) with breast cancer
^eBreast density assessed with Magnetic Resonance Imaging according to the ACR BI-RADS Magnetic Resonance Imaging categories a, b, c, d. In this study, c and d categories of breast density are defined as dense breast. On the other hand, the, a and b categories of breast density are defined as nondense breast

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