Background: Endocrine therapy (ET) is the standard of care for postmenopausal (PM) women with early stage breast cancer (EBC). Studies suggest higher risk of vascular toxicities (VT) on aromatase inhibitor (AI) therapy. We report incidence/discontinuation rates of VTs in a cardiac clinic. Methods: PM women with hormone receptor positive EBC treated with ET (tamoxifen (T) ± AI) at Ottawa Hospital Cancer Center 01/99-2/06. Data included: demographics, vascular co-morbidities (VCM), ET, duration, VTs. Results: 626 pts, median age 59 years (r: 30-92), median follow-up 98 months (m), stage: I (196 pts), II (341 pts) III (89 pts) EBC. Majority (52.5%) pts had VCM at ET initiation; hypertension (HTN) (36%), hyperlipidemia (HYLP) (17%), coronary disease (12%), thrombosis (9%), angina (6%) TIA (6%). Treatment discontinued due to VT 3x more with T vs. AI. Most common VTs: edema, arrhythmias (ARR), cardiovascular (CVS) event, and HYLP. With Letrozole and T, previous VCM significantly increased risk of developing VT (chi-square: P=0.022 and 0.009). Time to develop VT shortest for T and exemestane. Previous VCM did not affect this interval. Longer exposure to T correlated with higher VT rate (t-test: p=0.046) not seen with AIs. Exposure to multiple AIs associated with higher VT rate (t-test: p=0.009). Conclusions: This cohort study reports similar VT rates with AI therapy as reported in the literature. T was associated with higher discontinuation rates (10.5%) due to VTs compared to AIs (2.8-3.3%). Longer duration of AI therapy was not associated with increased risk of VTs. These encouraging results reflect the real-life experience of women exposed to ET.

	Tamoxifen (n=369)	Anastrozole (n=444)	Exemestane (n=62)	Letrozole (n=211)
Mean time on treatment (m)	36	48	30	42
Mean time until VT (m)	14.3	20.4	16.0	21.8
Discontinuation from VT	10.5%	3.3%	3.2%	2.8%
VTs developed (%)
Edema*	23.3	21.2	17.7	13.7
HYLP	1.4	4.1	3.2	7.1
CVS**	3.5	3.6	3.2	6.6
Cerbrovascular***	2.7	2.3	3.2	3.3
HTN	1.6	2.3	4.8	3.3
ARR	2.7	6.8	4.8	2.8
Thromboembolic event	7.3	3.8	1.6	0.9

Abbreviation: n, number pts treated: may have multiple treatments.

* peripheral, generalized

** ischemic heart disease, heart failure, valve disease

*** thrombosis, embolism, hemorrhage