TABLE III.

Multivariate Cox proportional hazards models for estimating the effect of period of clinical practice in 317 patients with early-stage breast cancer positive for the estrogen or progesterone receptor, with 1–3 positive lymph nodes, adjusted for radiation therapy, endocrine therapy, and comorbidity

Variable	Survival
	Disease-free			Overall
	hr	95% ci	ρ	hr	95% ci	ρ
Period of clinical practicea (2000–2002 vs. 1995–1997)	0.98	0.648 to 1.472	0.91	0.86	0.54 to 1.37	0.51
Adjuvant radiation therapy (yes vs. no)	0.46	0.327 to 0.750	0.0009	0.43	0.26 to 0.7	0.0007
Adjuvant endocrine therapy (yes vs. no)	0.87	0.57 to 1.31	0.5	0.79	0.49 to 1.27	0.33
Co-morbidity (≥1 vs. 0)	2.02	1.279 to 3.181	0.0025	2.78	1.69 to 4.59	<0.0001

^aThe effect of adjuvant chemotherapy administration independent of the effect of adjuvant radiation therapy, adjuvant endocrine therapy, and comorbidity.

hr = hazard ratio; ci = confidence interval.