Table 4. Multivariate Cox Proportional Hazards Models¹ within Groups -Time to Late GI/GU Grade 2+ Toxicity.

Disease Group	Covariate	Comparison	Hazard Ratio*	(95% CI)	p-value**
Group 1 (n=499)		Dose Level I vs. Dose Level V	RL 1.84	(1.10, 3.08)	0.0212††
		Dose Level II vs. Dose Level V	RL 2.00	(1.22, 3.28)	0.0062††
		Dose Level III vs. Dose Level V	RL 2.17	(1.31, 3.59)	0.0025††
		Dose Level IV vs. Dose Level V	RL 1.43	(0.93, 2.18)	0.1028
	3D Margins	Continuous	1.121	(1.016, 1.236)	0.0222††
Group 2 (n=436)		Dose Level I vs. Dose Level V	RL 1.96	(0.94, 4.07)	0.0723
		Dose Level II vs. Dose Level V	RL 2.59	(1.51, 4.43)	0.0005††
		Dose Level III vs. Dose Level V	RL 2.10	(1.17, 3.77)	0.0135††
		Dose Level IV vs. Dose Level V	RL 1.59	(1.04, 2.45)	0.0339††
	3D Margins	Continuous	1.031	(0.934, 1.138)	0.5476
Group 3 (n=90)‡	Age	< 70 vs. ≥ 70	RL 0.88	(0.46, 1.68)	0.6999
	Induction Hormones	No vs. Yes	RL 0.76	(0.32, 1.82)	0.5323
	3D Margins	Continuous	0.978	(0.883, 1.148)	0.7840

¹age (< 70 vs. ≥ 70) and induction hormone administration (yes vs. no), are adjusted for in all models.

^*Hazard ratio: A hazard ratio quantifies how much more (less) risk patients at some level have than those at the reference level (RL). A confidence interval that includes 1 indicates no difference exists between the subgroups.

^**p-value from Chi-square test using the Cox proportional hazards model

^‡This is based only on the 93 patients from dose level 2 with late toxicity information; the 4 patients from dose level 1 with late toxicity information were excluded from this analysis.

^††It is statistically significant at the significance level of 0.05

Group 1 = 9 missing 3D margin data;Group 2 = 7 missing 3D margin data;Group 3 = 3 missing 3D margin data