Natural history of malignant bone disease in breast cancer and the use of cumulative mean functions to measure skeletal morbidity

Table 6 Full multivariate analysis for first skeletal-related event

Variable	RR	(95% CI)	p value
Age ≥ 50 years	1.12	(0.69, 1.83)	0.651
ECOG performance status
2 – 3 versus 0 – 1	1.33	(0.78, 2.25)	0.296
Hydroxyproline/Creatinine ratio (centered)	0.97	(0.92, 1.03)	0.292
Bone-specific alkaline phosphatase, U/L	1.01	(1.00, 1.02)	0.083
Estrogen-receptor status versus negative
Positive	0.94	(0.50, 1.76)	0.838
Unknown	0.91	(0.35, 2.36)	0.844
Progesterone-receptor status versus negative
Positive	0.80	(0.41, 1.55)	0.506
Unknown	1.19	(0.51, 2.81)	0.685
Sites of metastasis (yes versus no)
Bone as only metastatic site	0.81	(0.45, 1.44)	0.467
Lung	1.49	(0.70, 3.20)	0.306
Liver	0.98	(0.48, 1.99)	0.960
Time from diagnosis of bone metastases to study entry, years	1.01	(0.84, 1.20)	0.992
Time from cancer diagnosis to study entry, years	0.97	(0.91, 1.04)	0.395
Lesion characteristics and numbers
≥ 3 osteolytic versus < 3 osteolytic	1.53	(0.96, 2.44)	0.071
1 – 2 osteoblastic versus no osteoblastic	1.70	(1.01, 2.86)	0.045
≥ 3 osteoblastic versus no osteoblastic	0.70	(0.24, 2.08)	0.525
1 – 2 mixed versus no mixed	1.16	(0.57, 2.33)	0.687
≥ 3 mixed versus no mixed	1.47	(0.72, 3.01)	0.291
Prior fracture (yes versus no)	0.83	(0.44, 1.58)	0.577
Pain scores (centered)	1.27	(1.15, 1.40)	< 0.001
Prior chemotherapy (yes versus no)	1.07	(0.33, 3.41)	0.915
≥ 2 prior hormonal therapies (yes versus no)	1.00	(0.62, 1.62)	1.000
Prior radiotherapy (yes versus no)	1.84	(1.11, 5.03)	0.018

Values in bold represent statistically significant correlations.
RR = Relative risk, CI = Confidence interval, ECOG = Eastern Cooperative Oncology Group, U = Units.

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