Table 2.

Univariable and Multivariable Predictors of SRE Among Patients With mCRPC

Variables	Univariable Results			Model Selectiona
	HR	95% CI	P	HR	95% CI	P
Age at metastases, y	0.99	0.97–1.01	0.318
Year of metastases	0.91	0.85–0.97	0.005	0.93	0.87–0.99	0.028
Race			0.069
Non-black	Referent
Black	0.65	0.41–1.03
Treatment center			0.508
Center 1	Referent
Center 2	0.87	0.57–1.33
Biopsy Gleason score			0.233	Referent
2–6	Referent			-
7	0.89	0.43–1.86		1.74	1.02–2.96	0.041
8–10	1.58	0.79–3.17		1.54	0.90–2.62	0.112
Unknown/No Biopsy	1.19	0.59–2.41
Primary localized treatment			0.064
None	Referent			Referent
Radical Prostatectomy ± Radiation	1.38	0.75–2.53		-
Radiation Alone	1.82	1.09–3.03		2.33	1.50–3.62	<0.001
Number of bone metastases			0.107
1	Referent			Referent
2	0.42	0.17–1.06
3–9	0.88	0.51–1.52
≥10	1.26	0.70–2.27		1.60	1.00–2.57	0.052
PSA at metastases (ng/mL)	1.13	0.98–1.30	0.102
PSADT at metastases (months)
<9	Referent
≥9	0.50	0.29–0.86	0.011
Missing	0.96	0.57–1.61	0.880
Months from ADT to CRPC	1.00	0.99–1.01	0.948
Months from CRPC to metastases	0.99	0.98–1.00	0.078
Bone pain
No	Referent			Referent
Yes	3.34	2.04–5.48	<0.001	3.64	2.30–5.75	<0.001
Unknown	0.84	0.39–1.83	0.667	-

Abbreviations: 95% CI, 95% confidence interval; ADT, androgen deprivation therapy; HR, hazard ratio; mCRPC, metastatic castration-resistant prostate cancer; PSA, prostate-specific antigen; PSADT: prostate-specific antigen doubling time; RT, radiotherapy; SRE: skeletal-related event

^aForward selection with α=0.2