Table 3.

Multivariable analysis for IIEF score

Variables	Variable categories	Estimate	Standard deviation	P value
IIEF score at 6 months
RT method	3D-CRT vs IMRT*	2.79	1.75	.11
Age	<70 vs ≥70 y*	15.04	1.63	<.001
Race	White* vs non-White	2.07	2.30	.37
Time	Baseline vs 6 mo*	5.45	0.66	<.001
Treatment arm	3D-CRT/IMRT 70.2Gy vs 3D-CRT/IMRT 79.2Gy*	−2.06	1.62	.20
IIEF score at 12 months
RT method	3D-CRT vs IMRT*	2.29	1.55	.14
Age	<70 vs ≥70 y*	15.00	1.47	<.001
Race	White* vs non-White	4.19	2.22	.06
Time	Baseline vs 12 mo*	6.50	0.65	<.001
Treatment arm	3D-CRT/IMRT 70.2Gy vs 3D-CRT/IMRT 79.2Gy*	−1.20	1.46	.41
IIEF score at 24 months
RT method	3D-CRT vs IMRT*	−0.33	1.59	.83
Age	<70 vs ≥70 y*	14.38	1.47	<.001
Race	White* vs non-White	5.74	2.18	.009
Salvage hormones	Yes* vs No	7.19	3.13	.022
Treatment arm	3D-CRT/IMRT 70.2Gy vs 3D-CRT/IMRT 79.2Gy*	1.59	3.74	.67
Treatment arm*Salvage hormones		−2.78	4.08	.49
Time	Baseline vs 24 months*	8.59	0.71	<.001
IIEF score at 6, 12, and 24 months
Baseline score		0.65	0.02	<.001
RT method	3D-CRT vs IMRT *	1.09	0.96	.25
Age	<70 vs ≥70 y*	4.69	0.94	<.001
Race	White* vs non-White	0.23	1.29	.86
Salvage hormones	Yes* vs No	2.26	2.04	.27
Treatment arm	3D-CRT/IMRT 70.2Gy vs 3D-CRT/IMRT 79.2Gy*	2.42	2.43	.32
Treatment arm*Salvage hormones		−0.38	2.62	.89
Time		−1.91	0.35	<.001
IIEF single-item erectile dysfunction score at 6, 12, and 24 months†
Baseline score		0.56	0.02	<.001
RT method	3D-CRT vs IMRT*	0.02	0.09	.86
Age	<70 vs ≥70 y*	0.41	0.08	<.001
Race	White* vs non-White	0.07	0.11	.53
Time		−0.17	0.032	<.001
Treatment arm	3D-CRT/IMRT 70.2Gy vs 3D-CRT/IMRT 79.2Gy*	0.13	0.080	.093

Abbreviations: 3D-CRT = 3-dimensional conventional radiation therapy; IIEF = International I= intensity lated radiation therapy.

^*Indicates the reference level.

^†Single item: “How often were you able to get an erection during sexual activity?”