Adapted from the NCI Cancer Bulletin, vol. 6/no. 18, September 22, 2009 (see the current issue).
Women who use combination hormone therapy to treat menopausal symptoms may be at an increased risk of dying from lung cancer. An analysis of data from the Women's Health Initiative (WHI) study has found that, although the use of estrogen-plus-progestin therapy did not increase lung cancer incidence, it did increase the number of deaths from the disease, primarily from non-small cell lung cancer. The results appeared online September 18, 2009 in The Lancet.
"We have identified a new potentially lethal side effect of using estrogen-plus-progestin therapy over a relatively short period of time," said lead investigator Dr. Rowan Chlebowski of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center. Postmenopausal women considering this therapy should be aware of the risk, especially those who are current or long-term former smokers, he added.
In 2002, the WHI ended early when an increased risk of breast cancer was found in women using combination hormone therapy compared with nonusers. Studies since then have shown that the increased breast cancer risk persists even after the hormones are stopped and that hormone use interferes with the detection of breast cancer, causing some women to have abnormal mammograms for at least a year. Hormone therapy has also been linked to an increased risk of ovarian cancer.
A potential mechanism to explain the new findings may be estrogen's ability to stimulate blood vessel growth (angiogenesis), the researchers said, noting that strategies to block the growth of tumor blood vessels are used in both lung and breast cancer treatment. Another factor in the lung cancer deaths may have been that hormones delayed the detection of lung tumors, as has happened in breast cancer.
An accompanying editorial agreed that women at risk of lung cancer should avoid hormone therapy and asked whether this treatment has "any role in medicine today." In addition, Dr. Apar Kishor Ganti of the University of Nebraska Medical Center noted that because the WHI was a randomized controlled trial, which is the gold standard in medicine, the results should dispel any notions that hormones may have protective effects against lung cancer, as several retrospective studies have suggested.