Tamoxifen is not detrimental to endothelial function in postmenopausal women with breast cancer.
BACKGROUND
Tamoxifen has mixed estrogen agonist and antagonist properties in estrogen-regulated tissues. Its effect on the cardiovascular system is not well defined. We carried out a study to investigate the effect of tamoxifen on peripheral vascular endothelial function.


METHODS
Three groups of postmenopausal women (median age, 56 years; range, 39 to 69 years) with breast cancer were studied. Patients in group 1 (n = 10) were newly diagnosed with breast cancer and studied before and after 4 weeks treatment with tamoxifen. Group 2 women (n = 6) had been receiving long-term tamoxifen (3 to 5 years) and were studied while taking tamoxifen and 4 weeks after stopping it. The final group of 6 subjects were in remission from primary breast cancer and were not receiving or had previously received tamoxifen. Ultrasound assessments of endothelial function were done before and 4 weeks after the initiation or discontinuation of tamoxifen with the nontreatment group acting as control. All ultrasound imaging was made by a single investigator blinded to the therapeutic status of the subject. Brachial artery diameter was measured by ultrasound at baseline and 1 minute after reactive hyperemia. Flow-mediated reactivity (FMR) was defined as percent change in artery diameter from baseline 1 minute after reactive hyperemia.


RESULTS
There was no change in FMR in patients before compared with 4 weeks after starting tamoxifen (4.06% +/- 1.44% vs 3.97% +/- 1.20%, respectively, mean +/- standard error of the mean [SEM], P =.97). There was no significant change in FMR on withdrawal from tamoxifen (1.84% +/- 1.98% vs -0.42% +/- 1.44% on tamoxifen vs off tamoxifen, mean +/- SEM, P =.36). FMR in subjects taking tamoxifen was no different from the control group (3.17% +/- 1.05% vs 3.16% +/- 0.91%, respectively, mean +/- SEM, P =.995).


CONCLUSIONS
Tamoxifen does not appear to affect endothelial function in the short term in postmenopausal women with breast cancer.
Ong
P J
PJ
Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College School of Medicine, London, UK.
Linardou
H
H
Graham
H A
HA
Savage
P
P
Hayward
C S
CS
Coombes
R C
RC
Collins
P
P
D000328:Adult; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D001161:Arteriosclerosis / Q000503:physiopathology / Q000517:prevention & control; D001916:Brachial Artery / Q000187:drug effects / Q000502:physiology; D001943:Breast Neoplasms / Q000188:drug therapy*; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D005260:Female; D018056:Hemorheology / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D017698:Postmenopause; D012039:Regional Blood Flow / Q000187:drug effects; D013629:Tamoxifen / Q000494:pharmacology / Q000627:therapeutic use*; D018608:Ultrasonography, Doppler / Q000706:statistics & numerical data
D018931:Antineoplastic Agents, Hormonal; D013629:Tamoxifen