covering seven observational studies and a total population of over 4.5 million people.
The data, published in JAMA Dermatology, are “reassuring,” the authors reported, considering that the spironolactone label carries a Food and Drug Administration warning regarding possible tumorigenicity, which is based on animal studies of doses up to 150-fold greater than doses used for humans. The drug’s antiandrogenic properties have driven its off-label use as a treatment for acne, hidradenitis, androgenetic alopecia, and hirsutism.
Spironolactone, a synthetic 17-lactone steroid, is approved for the treatment of heart failure, edema and ascites, hypertension, and primary hyperaldosteronism. Off label, it is also frequently used in gender-affirming care and is included in Endocrine Society guidelines as part of hormonal regimens for transgender women, the authors noted.
The seven eligible studies looked at the occurrence of cancer in men and women who had any exposure to the drug, regardless of the primary indication. Sample sizes ranged from 18,035 to 2.3 million, and the mean age across all studies was 62.6-72 years.
The researchers synthesized the studies, mostly of European individuals, using random effects meta-analysis and found no statistically significant association between spironolactone use and risk of breast cancer (risk ratio, 1.04; 95% confidence interval, 0.86-1.22). Three of the seven studies investigated breast cancer.
There was also no significant association between spironolactone use and risk of ovarian cancer (two studies), bladder cancer (three studies), kidney cancer (two studies), gastric cancer (two studies), or esophageal cancer (two studies).
For prostate cancer, investigated in four studies, use of the drug was associated with decreased risk (RR, 0.79, 95% CI, 0.68-0.90).
Kanthi Bommareddy, MD, of the University of Miami and coauthors concluded that all studies were at low risk of bias after appraising each one using a scale that looks at selection bias, confounding bias, and detection and outcome bias.
In dermatology, the results should “help us to take a collective sigh of relief,” said Julie C. Harper, MD, of the Dermatology and Skin Care Center of Birmingham, Ala., who was asked to comment on the study. The drug has been “safe and effective in our clinics and it is affordable and accessible to our patients,” she said, but with the FDA’s warning and the drug’s antiandrogen capacity, “there has been concern that we might be putting our patients at increased risk of breast cancer [in particular].”
The pooling of seven large studies together and the finding of no substantive increased risk of cancer “gives us evidence and comfort that spironolactone does not increase the risk of cancer in our dermatology patients,” said Dr. Harper, a past president of the American Acne & Rosacea Society.
“With every passing year,” she noted, “dermatologists are prescribing more and more spironolactone for acne, hidradenitis, androgenetic alopecia, and hirsutism.”
Four of the seven studies stratified analyses by sex, and in those without stratification by sex, women accounted for 17.2%-54.4% of the samples.
The studies had long follow-up periods of 5-20 years, but certainty of the evidence was low and since many of the studies included mostly older individuals, “they may not generalize to younger populations, such as those treated with spironolactone for acne,” the investigators wrote.
The authors also noted they were unable to look for dose-dependent associations between spironolactone and cancer risk, and that confidence intervals for rarer cancers like ovarian cancer were wide. “We cannot entirely exclude the potential for a meaningful increase in cancer risk,” and future studies are needed, in populations that include younger patients and those with acne or hirsutism.
Dr. Bommareddy reported no disclosures. Other coauthors reported grants from the National Cancer Institute outside the submitted work, and personal fees as a Cancer Prevention and Research Institute of Texas Scholar in Cancer Research. There was no funding reported for the study. Dr. Harper said she had no disclosures.