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.
Researchers writing in the journal Cancer suggested that newer estrogen blockers on the market, including the osteoporosis drug raloxifene and a class of drugs called aromatase inhibitors, may also be able to slow the progression of lung cancer.
Estrogen blockers such tamoxifen and the aromatase inhibitors have significant side effects and are generally used only for women past menopause. So they're unlikely to become drugs for the prevention of lung cancer, as they currently are for breast cancer. But as researchers learn more about lung cancer and study whether early detection of this deadly cancer can save lives, the role of estrogen in helping those cancers take hold and grow will likely get more attention.