Doctors in Taiwan have found that people who take a common type of blood pressure drug appear less likely to develop cancer than patients not taking the medication.
Their report adds to a conflicting array of studies on this type of medicine, called angiotensin II receptor blockers (ARBs), and one U.S. expert called the new results “unreliable.”
ARBs include Novartis’s Diovan, Merck’s Cozaar, and Avapro from Bristol-Myers Squibb and Sanofi-Aventis. Some 200 million people around the world are currently taking one of the drugs.
While previous research had tied them to a slight increase in cancer risk, “From our observation in the real world, ARBs are safe and may provide benefit beyond lowering blood pressure,” said Dr. Hsin-Bang Leu of Taipei Veterans General Hospital in Taiwan, whose findings appear in the American Journal of Cardiology.
Leu and colleagues studied more than 100,000 patients, identified from an insurance database, who had been diagnosed with high blood pressure between 1998 and 2006. Over an average of six years, eight percent developed some form of cancer.
The patients on ARBs – about 37 percent – had a considerably lower cancer risk. Even after accounting for the influence of other diseases and blood pressure meds, their chances of developing cancer were 33 percent lower than among patients not taking the drugs.
And the longer a patient had been on ARBs, the greater the apparent effect. After a year or more, for instance, the team found a 50 percent lower risk of cancer.
In an e-mail, Leu said it is possible that ARBs protect against cancer by thwarting certain molecular steps in the transition of normal cells to cancer cells, or in the spread of the rogue cells.
But a U.S. expert said he did not believe the drugs can stave off cancer.
“It is just an illusion due to poor research technique,” Dr. Ilke Sipahi of Case Western University in Cleveland told Reuters Health by e-mail.
He added that there were “major imbalances” between the patients receiving and not receiving ARBs.
“Patients receiving ARBs were receiving better care overall,” suggested Sipahi, who recently found in a review of the medical literature that the drugs were linked to an increased cancer risk.
“Poor treatment – perhaps including no advice on smoking cessation and poor socioeconomic status and unhealthy living conditions – led to the more frequent cancers in the control group.”
The Taiwanese researchers acknowledged that they were not able to account for these factors in the study. Still, Leu emphasized that patients who are taking ARBs should not worry about it increasing their risk of cancer.
Sipahi, too, cautioned against taking any drastic actions based on the research. “Patients should not stop or change any of their treatments without discussing these issues and their options with their physicians,” he said.
Last year, Bristol-Myers and Sanofi told Reuters “no signal for new cancers has been found” in the companies’ ongoing review of health problems reported in patients treated with Avapro.
Other common blood pressure drugs include “water pills,” or diuretics, as well as beta blockers such as atenolol and ACE inhibitors such as Pfizer’s Accupril.
SOURCE: American Journal of Cardiology, online January 24, 2011.