Table 3. 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=501)		Dose Level I vs. Dose Level V	RL 1.90	(1.14, 3.17)	0.0140††
		Dose Level II vs. Dose Level V	RL 2.15	(1.32, 3.50)	0.0020††
		Dose Level III vs. Dose Level V	RL 2.10	(1.27, 3.48)	0.0039††
		Dose Level IV vs. Dose Level V	RL 1.37	(0.89, 2.09)	0.1506
	PTVHD volume	Continuous	1.004	(1.001, 1.006)	0.0028††
Group 2 (n=435)		Dose Level I vs. Dose Level V	RL 2.01	(0.97, 4.16)	0.0603
		Dose Level II vs. Dose Level V	RL 2.62	(1.55, 4.43)	0.0003††
		Dose Level III vs. Dose Level V	RL 2.02	(1.14, 3.59)	0.0168††
		Dose Level IV vs. Dose Level V	RL 1.69	(1.10, 2.60)	0.0165††
	PTVHD volume	Continuous	1.003	(1.000, 1.006)	0.0330††
Group 3 (n=93)‡	Age	< 70 vs. ≥ 70	RL 0.92	(0.48, 1.74)	0.7901
	Induction Hormones	No vs. Yes	RL 0.76	(0.32, 1.85)	0.5494
	PTVHD volume	Continuous	1.002	(0.997, 1.007)	0.4660

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 = 7 missing PTVHD volume data; Group 2 = 8 missing PTVHD volume data