Researchers from the Johns Hopkins Bloomberg School of Public Health combined in vitro cell culture laboratory studies with a large epidemiologic cohort study to determine that digoxin — a cardiac drug derived from the foxglove plant used to treat congestive heart failure and heart rhythm abnormalities — may also lower a patient’s risk for prostate cancer by 24 percent.
Published in the journal Cancer Discovery, researchers delved into their scientific exploration by first singling out 38 non-chemotherapy drugs from a database of over 3,000 compounds with a history of medical use. The drugs were then assessed for their ability to reduce prostate cancer cell growth in the lab.
Based on its potency in cell growth assays, digoxin was selected as a good candidate for further study among a cohort of patients with reliable health information available.
Next, Dr. Elizabeth Platz, professor of epidemiology, oncology and urology at Johns Hopkins, analyzed data on 47,000 men between the ages of 40 and 75 who participated in the Harvard Health Professionals Follow-up Study from 1986 to 2006 and were cancer-free at the outset of the study. There were 5,002 cases of prostate cancer reported among the participants. Those who used digoxin regularly — approximately 940 men — had a 24 percent lower relative risk of getting prostate cancer, while men who took the drug for longer than ten years lowered their risk by half compared to those not taking digoxin.
The study authors caution, however, that this study does not prove that digoxin actually reduces the risk of prostate cancer and that the drug should not be used to prevent prostate cancer, especially not in otherwise healthy individuals.
While ACSH's Dr. Gilbert Ross finds the results impressive and admires the study design, he explains that, “Digoxin is commonly used to treat many types of heart disease in patients who experience heart failure or irregular heart rhythms — including atrial fibrillation.” However, the drug does have serious drawbacks: “The therapeutic index is quite small, relatively speaking, meaning that even a small excess of the drug can have serious, even lethal, effects.”
ACSH’s Dr. Josh Bloom is concerned that the toxicity of digoxin and its efficacy may go hand in hand. “It will be very interesting to see if less toxic drugs from the in vitro panel show the same effect.”
