Safety and Efficacy of Long-Term Zoledronic Acid in Advanced Breast Cancer with Bone Metastasis in South China

Table 1

Clinical characteristics of patients with advanced breast cancer and bone metastasis between group A (ZA 6–24 months) and group B (ZA > 24 months).

Parameter		Group A (ZA 6–24 months, n = 293)	Group B (ZA > 24 months, n = 273)	value
Age at BM	Median (range)	47 (19, 77)	47 (25, 76)	0.869
Time from BC to BM	Median (range)	30.6 (0, 343.2)	33.9 (0, 279.6)	0.186
Age group	<50 years	176 (60.1%)	164 (60.1%)	0.999
	≥50 years	117 (39.9%)	109 (39.9%)
Menstrual status^a	Perimenopause	152 (51.9%)	144 (52.7%)	0.836
	Postmenopause	141 (48.1%)	129 (47.3%)
Performance status	0–1	230 (78.5%)	231 (84.6%)	0.061
	≥2	63 (21.5%)	42 (15.4%)
Pathological subtype	Invasive ductal carcinoma	276 (94.2%)	261 (95.6%)	0.707
	Invasive lobular carcinoma	11 (3.8%)	7 (2.6%)
	Other type	6 (2.0%)	5 (1.8%)
T stage	T1/T2	199 (67.9%)	191 (70.0%)	0.119
	T3/T4	73 (24.9%)	73 (26.7%)
	Unknown	21 (7.2%)	9 (3.3%)
Lymph node	N0	66 (22.5%)	75 (27.5%)	0.174
	N1–3	227 (77.5%)	198 (72.5%)
ER	Negative	82 (28.0%)	40 (14.7%)	<0.001
	Positive	211 (72.0%)	233 (85.3%)
PR	Negative	101 (34.5%)	52 (19.0%)	<0.001
	Positive	192 (65.5%)	221 (81.0%)
HER2	Negative	175 (59.7%)	193 (70.7%)	0.011
	Positive	114 (38.9%)	74 (27.1%)
	Unknown	4 (1.4%)	6 (2.2%)
Number of bones involved	≤3	141 (48.1%)	139 (50.9%)	0.507
	>3	152 (51.9%)	134 (49.1%)
Involved bones^b	Non-load-bearing bone	42 (14.3%)	34 (12.5%)	0.512
	Load-bearing bone	251 (85.7%)	239 (87.5%)
Stage of bone metastasis	Primary	55 (18.8%)	53 (19.4%)	0.846
	Subsequent	238 (81.2%)	220 (80.6%)
Other organ metastasis^c	Nonvisceral organ	91 (31.0%)	96 (35.2%)	0.299
	Visceral organ	202 (69.0%)	177 (64.8%)
Systematic therapy	Chemotherapy	250 (85.3%)	227 (83.2%)	0.478
	Endocrine therapy	194 (66.2%)	206 (75.5%)	0.016
	Target therapy	58 (19.8%)	54 (19.8%)	0.996

BC: breast cancer, BM: bone metastasis, M: month, ER: estrogen receptor, PR: progesterone receptor; ZOL: zoledronic acid, CNS: central nervous system. Data are presented as median (range) and are compared using the Mann–Whitney U Test. ^aPerimenopause is defined as bone metastasis that occurs before menopause, while bone metastasis that occurs after menopause is defined as postmenopause. ^bLoad-bearing bones consist of the spine, pelvis, and the limbs; these are strongly influenced by muscle strength, which affects the healing of fractures, bone grafts, osteotomies, and arthrodesis. The remainder are non-load-bearing bones, such as the skull, rib, clavicle, humerus, and ulna. ^cNonvisceral organ metastasis includes bone, lymph node, soft tissue, chest wall, and ipsilateral breast cancer. ^dCases were grouped by bone metastasis occurring at, or after, the diagnosis of breast cancer. Data are presented as number (percentage) of patients unless otherwise indicated. All categorical variables were compared by the Pearson χ2 or Fisher’s exact test.