Table 5. Multivariate (final) Cox proportional hazards model with left truncation assessing the impact of lenalidomide treatment and baseline factors on OSa.

Variable	Mortality
	HR (95% CI)	P-value
Lenalidomide-treated vs untreated cohort	0.597 (0.399–0.894)	0.012
Age, years	1.049 (1.034–1.065)	<0.001
Gender (female vs male)	0.598 (0.434–0.824)	0.002
RBC transfusion burden, units/8 weeks	1.056 (1.003–1.111)	0.037
Hemoglobin level, g/dl	0.883 (0.790–0.987)	0.028
Platelet count, × 109/l	0.999 (0.998–1.000)	0.035

^aLenalidomide treatment, although not significant in the univariate models, was forced to remain in the final models to estimate the magnitude of risk associated with lenalidomide in the presence of other risk factors. Complete covariate data were available for 243 of the lenalidomide-treated patients and 98 of the untreated patients.