Table 4.

Adjusted hazard ratios and 95% confidence intervals for the association of 6+ months concomitant inhibitor use with SBCE and breast cancer-specific mortality, by inhibitor strength and CYP2D6 metabolic phenotype.

	SBCE			BC mortality
Concomitant use category	PT	Events	aHRa (CI)	PT	Events	aHRa (CI)
No concomitant use	2,078,079	176	1.00 (ref.)	3,269,313	121	1.00 (ref.)
6+ months any inhibitor	649,861	50	0.7 (0.5,1.0)	1,064,189	33	0.7 (0.5,1.1)
6+ months strong or moderate	359,765	28	0.7 (0.5,1.1)	622,713	18	0.7 (0.4,1.1)
6+ months strong only	250,016	23	0.9 (0.5,1.4)	433,305	15	0.8 (0.5,1.4)

	SBCE		BC mortality
Concomitant use category	EM aHRa (CI)	IM/PM aHRa (CI)	EM aHRa (CI)	IM/PM aHRa (CI)
No concomitant use	1.00 (ref.)	1.4 (0.7,2.8)	1.00 (ref)	1.1 (0.5,2.2)
6+ months any inhibitor	0.6 (0.2,1.9)	0.8 (0.4,1.7)	0.6 (0.2,2.4)	0.5 (0.2,1.3)
6+ months strong or moderate	0.5 (0.1,2.4)	1.0 (0.4,2.3)	0.9 (0.2,4.6)	0.7 (0.2,1.8)
6+ months strong only	0.8 (0.2,3.9)	1.1 (0.5,2.8)	1.3 (0.3,6.7)	0.7 (0.2,2.1)

Abbreviations: aHR=adjusted hazard ratio, BC=breast cancer, CI=95% confidence interval, EM=extensive metabolizer, IM/PM=intermediate or poor metabolizer, PT=person-time in days, SBCE=second breast cancer events (recurrence or second primary BC)

^aHRs adjusted for age, BMI category, stage, grade, receipt of radiation and/or chemotherapy, and duration of adjuvant TAM.