Table 1. Patient characteristics.

GTV, gross tumor volume; BED, biologically effective dose at 3 Gy

^aInterval between CT simulation scan for radiation treatment planning and CT scan following radiation treatment

^bUsed immediately prior to, during, or in the follow-up period after radiotherapy

Continuous Variables			Change in GTV density (g/cm3)
	Median (range)		Spearman Correlation	p-value
Age (years)	64.9 (33.3-99.0)		-0.0406	0.6637
GTV (cc)	7.2 (0.24-38.8)		0.3026	0.0009
Follow-up Time (months)a	14.0 (9-25)		0.0398	0.6698
Dose (Gy)	30 (8-45)		0.0591	0.5268
Fractions	10 (1-15)		0.1109	0.2340
BED (Gy3)	60.0 (29.3-216.0)		-0.2861	0.0018
Discontinuous Variables		N (%)	Median (range)
Primary:	Breast	42 (35.9)	0.07 (-0.25-0.38)	0.0530
	Other	26 (22.2)	0.02 (-0.13-0.35)
	Prostate	24 (20.5)	0.09 (-0.15-0.5)
	Lung	15 (12.8)	-0.01 (-0.12-0.2)
	Myeloma	10 (8.6)	0.04 (-0.02-0.49)
Gender	Male	51 (43.6)	0.06 (-0.15-0.5)	0.1363
	Female	66 (56.4)	0.05 (-0.25-0.49)
Race	Caucasian	89 (76.1)	0.05 (-0.18-0.49)	0.7172
	African American	20 (17.1)	0.04 (-0.12-0.23)
	Other	8 (6.8)	0.13 (-0.25-0.50)
Androgen Ablationb	Yes	20 (17.1)	0.1 (-0.15-0.5)	0.0232
	No	97 (83.0)	0.04 (-0.25-0.49)
Denosumab/Bisphosphonatesb	Yes	56 (47.9)	0.05 (-0.18-0.5)	0.6272
	No	61 (52.1)	0.05 (-0.25-0.35)
Vertebral Level	Cervical	9 (7.7)	.15 (-0.25-0.28)	0.0971
	Thoracic	60 (51.2)	0.03 (-0.18-0.35)
	Lumbar	48 (41.0)	0.05 (-0.15-0.5)