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

Table 5

SREs in ABC with bone metastasis after treatment with ZA.

Type of SRE	Group A (ZOL 6–24 months); E = 178^a	Group B (ZOL > 24 months); E = 248^b	value
Pathological fracture	61 (34.3%)	78 (31.2%)	0.168
Spinal cord compression	50 (28.1%)	53 (21.4%)
Radiation to bone	58 (32.6%)	106 (42.7%)
Surgery to bone	9 (5.1%)	11 (4.4%)

E: event, SRE: skeletal-related event, ABC: advanced breast cancer, and ZA: zoledronic acid. All SREs are discussed separately and were compared by Pearson χ² test. ^{a, b}A total of 178 SREs occurred in all patients in group A and 250 SREs in group B, including the first and subsequent SREs.