Anatomical distribution of bone metastases in stage IV breast cancer: According to histological subtype

Table 1 Patients demographics

	Luminal A (n = 82)	Luminal B (n = 12)	Triple neg (n = 8)	HER 2 enrich (n = 5)	P value
Age at diagnosis	59.8 ± 12.4	58.7 ± 11.65	62.2 ± 15.8	56.21 ± 11.0	0.85
Metastasis-free survival (median, years)	2.55 (0.05-7.39)	2.75 (0.65-7.12)	1.14 (0.09-5.98)	0.37 (0.05-8.89)	0.98
BMI	26.8 ± 5.9	24.4 ± 5.7	26.3 ± 4.8	25.4 ± 8.3	0.58
Death	59 (72.8%)	9 (75%)	8 (100%)	3 (60%)	0.33

BMI: Body mass index.

Table 2 Anatomical distribution of first bone metastasis according to histological subtypes, n (%)

First bone metastasis	Luminal A (n = 82)	Luminal B (n = 12)	Triple neg (n = 8)	HER 2 enrich (n = 5)	P value
Skull bones	3/82 (3.7)	0	1/8 (12.5)	0	0.5
Scapula and clavicle	3/82 (3.7)	1/12 (8.3)	3/8 (37.5)	0	0.003
Sternum	7/82 (8.5)	2/12 (17)	1/8 (12.5)	2/5 (40)	0.16
Humerus	14/82 (17)	2/12 (17)	1/8 (12.5)	0	0.77
Ribs	24/82 (30)	2/12 (17)	1/8 (12.5)	4/5 (80)	0.041
Cervical vertebra	12/82 (15)	3/12 (25)	1/8 (12.5)	0	0.60
Thoracic vertebra	36/82 (44)	5/12 (45.5)	2/8 (25)	3/5 (60)	0.64
Lumbar vertebra	38/82 (46)	7/12 (58)	3/8 (37.5)	2/5 (40)	0.79
Sacrum	18/82 (22)	1/12 (8)	1/8 (12.5)	1/5 (20)	0.68
Pelvic bones (ilium, ischium, pubis)	43/82 (52)	5/12 (42)	5/8 (62.5)	3/5 (60)	0.80
Femoral head and neck	21/82 (26)	4/12 (33)	2/8 (25)	3/5 (60)	0.39
Femoral shaft and distal femur	20/82 (25)	3/12 (25)	2/8 (25)	3/5 (60)	0.38

Table 3 Anatomical distribution of second bone metastasis according to histological subtypes, n (%)

Second bone metastasis	Luminal A (n = 82)	Luminal B (n = 12)	Triple neg (n = 8)	HER 2 enrich (n = 5)	P value
Without bone progression	16/82 (19.5)	3/12 (25)	3/8 (37.5)	1/5 (20)	0.68
Skull bones	7/82 (9)	0	0	0	0.50
Scapula and clavicle	6/82 (7)	1/12 (8)	1/8 (12.5)	0	0.36
Sternum	7/82 (9)	0	0	0	0.50
Humerus	10/82 (12.5)	2/12 (17)	2/8 (25)	0	0.60
Ribs	28/82 (35)	2/12 (17)	0	1/5 (20)	0.13
Cervical vertebra	19/82 (24)	3/12 (25)	1/8 (12.5)	1/5 (20)	0.90
Thoracic vertebra	35/82 (44)	3/12 (25)	2/8 (25)	2/5 (40)	0.50
Lumbar vertebra	28/82 (35)	6/12 (50)	2/8 (25)	0	0.24
Sacrum	17/82 (21)	3/12 (25)	0	1/5 (20)	0.53
Pelvic bones (ilium, ischium, pubis)	31/82 (38)	7/12 (58)	0	3/5 (60)	0.046
Femoral head and neck	25/82 (31)	2/12 (17)	3/8 (37.5)	1/5 (20)	0.68
Femoral shaft and distal femur	24/82 (30)	2/12 (17)	2/8 (25)	1/5 (20)	0.77

Table 4 Pathologic and impending fractures according to histological subtypes, n (%)

Pathological fracture	Luminal A (n = 82)	Luminal B (n = 12)	Triple neg (n = 8)	HER 2 enrich (n = 5)	P value
Femoral head and neck	16 (20)	4 (33)	2 (25)	1 (20)	0.75
Spinal vertebrae	12 (15)	1 (8)	0	1 (20)	0.77
Humerus	5 (6)	1 (8)	1 (12.5)	0	0.78
Other1	8 (10)	0	1 (12.5)	0	0.63
Impending hip fracture	29 (35)	6 (50)	3 (37.5)	0	0.28

¹Other includes: Ribs, Tibia, Fibula and Pelvic bones.

Table 5 Anatomical distribution of first bone metastasis according to hormone receptor, n (%)

First bone metastasis	ER (n = 94)	PR (n = 59)	HER 2 (n = 16)	P value
Skull bones	3/94 (3.2)	1/59 (1.7)	0	1.00
Scapula and clavicle	4/94 (4.2)	3/59 (5)	1/16 (6.2)	0.93
Sternum	9/94 (9.6)	5/59 (8.5)	4/16 (25)	0.14
Humerus	16/94 (17.0)	10/59 (16.9)	2/16 (12.5)	0.89
Ribs	26/94 (28.0)	14/59 (24.1)	6/16 (37.5)	0.56
Cervical vertebra	15/94 (16.0)	10/59 (16.9)	3/16 (18.8)	0.96
Thoracic vertebra	41/94 (43.6)	23/59 (38.9)	8/16 (50)	0.62
Lumbar vertebra	45/94 (47.9)	25/59 (42.4)	8/16 (50)	0.76
Sacrum	19/94 (20.2)	10/59 (16.9)	2/16 (12.5)	0.72
Pelvic bones (ilium, ischium, pubis)	48/94 (51.1)	27/59 (45.8)	8/16 (50)	0.81
Femoral head and neck	25/94 (26.6)	18/59 (30.5)	7/16 (43.8)	0.37
Femoral shaft and distal femur	23/94 (24.7)	16/59 (27.6)	6/16 (37.5)	0.56