Table 3.

Multivariable Proportional Hazards Model of Salvage Radiotherapy and Interaction With PSA Doubling Time for Risk of Prostate Cancer–Specific Mortality, 1982–2004^a

Variables	No. of Deaths/No. of Individuals in Subgroup	HR (95% CI)	P Value
Time from surgery to recurrence, y		0.85 (0.77–0.94)b	.001
Calendar year of surgery		0.91 (0.86–0.95)b	<.001
Postoperative Gleason score
≤7	57/457	1 [Reference]
8–10	59/178	2.57 (1.75–3.77)	<.001
Salvage treatment			<.001c
PSA doubling time <6 mo
No salvage treatment	51/103	1 [Reference]
Radiotherapy only	4/29	0.14 (0.05–0.39)
Radiotherapy + hormonal	3/34	0.24 (0.07–0.77)
PSA doubling time ≥6 mo
No salvage treatment	38/294	1 [Reference]
Radiotherapy only	14/131	0.85 (0.45–1.59)
Radiotherapy + hormonal	6/44	0.66 (0.28–1.58)

Abbreviations: CI, confidence interval; HR, hazard ratio; PSA, prostate-specific antigen.

^aSurvival time measured from date of recurrence.

^bThe HR is per 1-year increase.

^cP value represents the likelihood ratio test for adding salvage treatment (2 variables) and 2 interaction terms to the model: likelihood ratio ${\chi }_4^2=28.7$.