Breast cancer in women using digoxin: tumor characteristics and relapse risk

Breast Cancer Research

Table 3 Hazard ratios for breast cancer relapse by time period of digoxin exposure

		First year			Subsequent years
	Digoxin-exposed	Person-years	Relapse, number	Hazard ratio (95% CI)	Person-years	Relapse, number	Hazard ratio (95% CI)
All	Yes	350	15	2.19 (1.26, 3.78)	1,521	54	0.99 (0.74, 1.32)
	No	30891	699	1,0	11,7143	4,338	1.0
Estrogen receptor status
Positive	Yes	285	13	2.51 (1.39, 4.55)	1,239	42	0.98 (0.71, 1.36)
	No	23,524	405	1.0	87,961	3,051	1.0
Negative	Yes	51	1	0.72 (0.10, 5.27)	229	9	0.97 (0.45, 2.09)
	No	6,404	262	1.0	23,852	1,083	1
Unknown	Yes	15	1	4.29 (0.43, 42.4)	53	3	1.27 (0.29, 5.58)
	No	963	32	1.0	5,330	204	1.0
Digoxin exposure with anti-estrogen treatment ¹
Tamoxifen	Yes	71	6	1.90 (0.81, 4.67)	282	20	0.89 (0.54, 1.47)
	No	5,382	185	1.0	18,360	1,246	1.0
Aromatase inhibitors	Yes	21	1	2.39 (0.26, 22.4)	58	3	1.63 (0.28, 9.43)
	No	1,037	12	1.0	1,430	75
Neither	Yes	193	8	1.76 (0.74, 4.21)	846	25	1.00 (0.65, 1.54)
	No	16,141	461	1.0	65,563	2.354	1.0

Risk compares patients (complete information only) using digoxin to those not using digoxin (referent) overall and by first and subsequent years after breast cancer diagnosis, by estrogen receptor status and allocated anti-estrogen treatment regimen. ¹Among tamoxifen and aromatase inhibitor users, hazard ratios for relapse in digoxin users for the first year and and at one year did not differ (P = 0.85 and P = 0.52, respectively).

ISSN: 1465-542X