Tamoxifen is the oldest of a wide array of medications that block the action of the hormone estrogen in the body. Researchers have found growing evidence in recent years that the majority of non-small cell lung cancers -- the most common form of lung cancer -- respond to estrogen with growth. So they wondered whether women taking tamoxifen as an adjunct to their breast cancer treatment might be less likely to develop or die of lung cancer.
Drawing from a meticulously maintained Swiss registry of cancer patients, researchers followed 6,665 breast cancer patients in the Swiss canton of Geneva, 3,066 of whom took tamoxifen following breast cancer treatment. The researchers found that the tamoxifen group was very slightly less likely to develop lung cancer than breast cancer survivors who did not take the drug. But the difference was so small that they concluded it could have been a statistical fluke.
But deaths from lung cancer were distinctly more numerous among the women who had not taken tamoxifen than among those who had -- a difference significant enough for researchers to declare that by shutting off one source of fuel to an incipient lung tumor, tamoxifen may slow progression of the disease once it has taken hold in a woman's lung.