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"These findings were the first, to our knowledge, demonstrating a survival benefit associated with the use of beta blockers and radiation therapy for lung cancer," said lead researcher Dr. Daniel Gomez, an assistant professor in the department of radiation oncology at the University of Texas M.D. Anderson Cancer Center in Houston.
"The results imply that there may be another mechanism, largely unexplored, that could potentially reduce the rates of tumor spread in patients with this very aggressive disease," he added.
The report was published Jan. 9 in the Annals of Oncology.
The investigators found that the 155 patients taking beta blockers for heart problems lived an average of almost two years, compared with an average of 18.6 months for patients not taking these drugs.
The findings held even after adjusting for other factors such as age, stage of the disease, whether or not chemotherapy was given at the same time, presence of chronic obstructive pulmonary disease and aspirin use, the researchers noted.
Beta blockers also improved survival without the disease spreading to other parts of the body and survival without the disease recurring, they added.
Beta blockers, however, made no difference in the length of survival without the disease progressing in the part of the lungs where it started, the study authors pointed out.
How beta blockers might slow cancer's spread isn't known. However, the researchers speculate that these drugs may work by suppressing a hormone called norepinephrine, which is known to promote the spread of cancer cells.
"Right now, we would not advocate that patients take beta blockers for this purpose, until these findings can be validated by prospective trials," Gomez said. "In addition, future studies will help us to understand if the mechanism that we propose is correct, and thus if beta blockers are indeed directly affecting the aggressiveness of this cancer or if these findings are due to the activation or inhibition of another pathway."
For one expert, the study raises more questions than it answers.
"It is unclear whether beta blockers need to be started before the cancer is found, or if they still have a utility once the diagnosis is made," said Dr. Len Horovitz, a pulmonologist at Lenox Hill Hospital in New York City.
In addition, Horovitz wonders whether other drugs that block hormones might serve the same purpose.
One thing is clear, however, he added. People should not start taking beta blockers in hopes of preventing or controlling lung cancer, he said.
Horovitz did say he thinks trials testing whether or not beta blockers or other hormone-blocking drugs prevent the spread of lung cancer should be done.
Although the study found a link between beta blocker use in patients undergoing radiation therapy and increased non-small-cell lung cancer survival, it did not prove cause-and-effect.
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