As well, they said, "meta-analyses are generally considered less convincing than a large prospective trial."
Nonetheless, Sipahi and colleagues concluded, the modest but significant safety signal warrants more investigation.
In the meantime, many doctors said prescribing patterns will probably not change.
"I do not believe that this study as a single source should drive clinical practice at this time," said Dr. Randy Wexler of Ohio State University Medical Center in Columbus. "My prescribing pattern will not change."
Wexler noted in an e-mail that meta-studies are only as good as the trials they include. "A meta-analysis may point in the direction of a problem," he said, but that problem then has to be confirmed. He said a meta-analysis once showed that calcium channel blockers increase the risk of stroke -- but subsequent studies showed that in fact some calcium channel blockers reduce that risk.
Dr. Scott Wright, of the Mayo Clinic in Rochester, Minn., called the finding "interesting and potentially concerning" but said he would wait for further studies.
And Dr. John Messmer, of Penn State College of Medicine in Hershey, Pa., said a "possible, inconclusive increased risk of cancer is not going to change" his use of the drugs.
On the other hand, he and several other doctors questioned said they prefer to use the less expensive angiotensin-converting enzyme (ACE) inhibitors and rely on the angiotensin-receptor blockers (ARBs) only when patients are intolerant of ACE inhibitor.
FULL LIST OF STUDY DRUGS: Micardis Targit Blopress Atacand Amias Ratcand Cozzar