Isla Mackenzie and colleagues conducted a
cohort study that was published in BMJ,
evaluating the risk of breast cancer in older women exposed to
spironolactone. Spironolactone is a potassium-sparing diuretic used in a number
of conditions like fluid retention, hypertension, low potassium levels and
heart failure. It acts as an aldosterone antagonist (a hormone produced by the
adrenal gland), and hence is useful in a condition called hyperaldosteronism.
It has progestogenic and anti-androgenic properties and therefore could
contribute to promoting breast cancer.
For the purpose of
study, around 1 290 625 female volunteers aged 55 years or above without any
previous history of breast cancer were enrolled. A volunteer was regarded as
exposed to spironolactone if she received two prescriptions of the drug after
the age of 55 years.
Two unexposed randomly
selected women served as controls for every woman exposed to spironolactone in
the study. Among the 28,032 females exposed to spironolactone and 55,961 not
exposed women, about 29,491new cases of breast cancer were reported.
It was observed that
the unadjusted rate of breast cancer was 0.39 percent per year for females
exposed to spironolactone against 0.38 percent per year for non-exposed
In the women exposed
to spironolactone, the prevalence of co-morbid heart failure and diabetes was
also high. Risk factors associate with breast cancer in the study population
included family history of breast cancer, exposure to multiple drug classes,
history of other cancers and exposure to steroids. The scientists were of the
opinion that there was no significant evidence to confirm that spironolactone
increases the prevalence of breast cancer in females over the age of 55 years
without any prior history of the disease. Moreover, no association was noticed
between the dose of spironolactone and the risk of breast cancer.
Spironolactone and risk of incident breast
cancer in women older than 55 years: retrospective, matched cohort study; Isla
Mackenzie et al; BMJ 2012;345:e4447