Pharmacogenetic testing affects choice of therapy among women considering tamoxifen treatment

Table 4 Association of therapeutic decision-making by clinical and breast cancer characteristics, CYP2D6 phenotype, previous knowledge of CYP2D6 testing, referral method, and interest in CYP2D6 testing

	Change to aromatase inhibitors
	Unadjusted	Adjusted^a
Characteristics	OR (95% CI) P -value	OR (95% CI) P -value
Age	1.03 (0.98, 1.08) 0.23	1.02 (0.95, 1.10) 0.50
Breast cancer type
Invasive breast cancer	-	-
Ductal carcinoma in situ (DCIS)	1.07 (0.32, 3.48) 0.90	1.33 (0.34, 5.11) 0.67
Lobular carcinoma in situ (LCIS)	0.82 (0.09, 6.76) 0.85	0.44 (0.03, 5.59) 0.53
Post-menopausal status	1.54 (0.51, 4.62) 0.43	1.78 (0.35, 9.08) 0.48
Report of any tamoxifen side effects (yes)	1.09 (0.34, 3.50) 0.87	0.61 (0.16, 2.31) 0.47
CYP2D6 phenotype
UM/EM^b	-	-
IM	0.56 (0.07, 4.59) 0.59	0.38 (0.04, 3.38) 0.38
PM	15.08 (4.26, 53.33) 0.0001	22.85 (5.28, 98.74) 0.0001
Previous knowledge of CYP2D6 testing (yes)	0.88 (0.33, 2.38) 0.81	0.91 (0.29, 2.84) 0.87
Referred by physician or nurse (yes)	0.60 (0.20, 1.81) 0.37	0.36 (0.09, 1.37) 0.13
Very interested in CYP2D6 testing before attending the educational session (versus somewhat and not really interested)	1.77 (0.49, 6.38) 0.38	3.01 (0.66, 13.65) 0.15

The number of participants followed up was 235. ^aOdd ratios adjusted for age, breast cancer type, menopausal status, report of any tamoxifen side effects, CYP2D6 phenotype, previous knowledge of CYP2D6 testing, referral method, and interest in CYP2D6 testing. P-value ≤ 0.05. ^bUltra-rapid metabolizer (UM) data combined with extensive metabolizer (EM) data. CI, confidence interval; DCIS, ductal carcinoma in situ; EM, extensive metabolizer; IM, intermediate metabolizer; LCIS, lobular carcinoma in situ; N, number of participants; OR, odds ratio; PM, poor metabolizer; UM, ultra-rapid metabolizer.

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