The PARP inhibitor olaparib potentiates the effect of the DNA damaging agent doxorubicin in osteosarcoma

Table 4 Multivariate Cox proportional hazard regression analysis for overall survival and relapse-free survival in overall osteosarcoma patients

Characteristics	OS	P	RFS	P
Characteristics	HR (95% CI)	P	HR (95% CI)	P
Multivariate analysis Model 1^a
Tumor size, cm, > 8 (vs. ≤ 8)	3.528 (0.937–13.284)	0.062
Age, yr., ≥ 30 (vs. < 30)			2.404 (0.918–6.301)	0.074
Stage, I	1	0.046	1	0.026
II	2.958 (0.333–26.295)	0.331	5.204 (0.641–42.213)	0.123
III-IV	1.631 (1.348–205.244)	0.028	21.071 (1.989–223.276)	0.011
γH2AX, positive (vs. negative)	12.239 (2.118–70.722)	0.005	5.212 (1.372–19.800)	0.015
Multivariate analysis Model 2^b
Tumor size, cm, > 8 (vs. ≤ 8)	3.158 (0.961–10.383)	0.058
Age, yr., ≥ 30 (vs. < 30)			2.565 (0.993–6.625)	0.520
CSddrm, score 3–4 (vs. score 0–2)	11.791 (2.427–57.294)	0.002	11.312 (2.513–50.913)	0.002

OS overall survival, RFS relapse-free survival, HR hazard ratio, 95% CI 95% confidence interval, CSddrm the combined score for the immunohistochemical expression of PARP1, γH2AX, BRCA1, and BRCA2
^aVariables considered in multivariate analysis Model 1 were age, tumor size, tumor stage, distant metastasis, histologic grade, and the expression of PARP1, γH2AX, BRCA1, and BRCA2
^bVariables considered in multivariate analysis Model 2 were age, tumor size, tumor stage, distant metastasis, histologic grade, and CSddrm

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