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

Breast Cancer Research

Table 2 Overall relapse hazard ratios for 33,496 women <74 years old with breast cancer and using digoxin

	Digoxin-exposed	Person-years	Relapse, number	Hazard ratio (95% CI)	P-value¹
All	Yes	1,872	69	1.13 (0.88, 1.46)	0.04
	No	148,034	5,037	1.0
Estrogen receptor status
Positive	Yes	1,524	55	1.15 (0.87, 1.52)	0.03
	No	111,485	3,456	1.0
Negative	Yes	280	10	0.93 (0.45, 1.90)	0.94
	No	30,256	1,345	1.0
Unknown	Yes	67	4	1.67 (0.49, 5.69)	0.53
	No	6,293	236	1.0
Digoxin exposure with anti-estrogen treatment ²
Tamoxifen	Yes	353	26	1.04 (0.68, 1.60)	0.36
	No	23,742	1,431	1.0
Aromatase inhibitors	Yes	79	4	1.87 (0.46, 7.56)	0.68
	No	2,467	87	1.0
Neither	Yes	1,038	33	1.10 (0.75, 1.61)	0.49
	No	81,704	2,815	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. ¹The P- value evaluates the overall digoxin effect on the hazard ratios for relapse, permitting different digoxin effects in the first year and later years of follow-up. ²Not presented are risks in subjects who switched between tamoxifen and aromatase inhibitors (that is, they were exposed to both at some time in their treatment) and those still in blinded protocols (exposure unknown).

ISSN: 1465-542X