Newswise — Women with advanced-staged lung cancer have a better overall survival rate than men, but there's a catch. The finding seems only to hold true for women 60 and older. For women under the age of 60, the survival rate drops to the same level as men.
"We don't know why, but the hypothesis is that age is acting as a surrogate for lower estrogen levels and those lower levels of estrogen may affect the metabolism of chemotherapy agents," explains Regina Vidaver Ph.D., executive director of the National Lung Cancer Partnership based in Madison, Wisc. The lower estrogen levels might actually make the treatments more effective.
But that's not where the sex differences end. There are many distinctions between men and women when it comes to lung cancer. Although lung cancer is the number one cause of cancer deaths among men and women in the United States, women who have never smoked are more at risk for the disease than men who never smoked. Some research indicates that the female hormone estrogen is involved in lung cancer risk in women. And when it comes to cigarettes and cancer, some evidence suggests women are more sensitive to the cancer-causing effects of chemicals in tobacco smoke.
At the 2007 Annual Meeting of the American Society for Clinical Oncology (ASCO), researchers presented data showing that pre-menopausal estrogen levels were associated with a higher death rate among women receiving chemotherapy for advanced non-small cell lung cancer (NSCLC), which makes up about 85 percent of all lung cancer cases.
Lung cancers can be divided into two types: small cell lung cancer and non-small cell lung cancer, terms describing how the cancer cells grow and spread in different ways. The data presented at ASCO reveals the potential role estrogen plays in interfering with standard treatment, namely chemotherapy, for lung cancer. And it further underscores the importance of sex-specific therapies.
There are many new treatments on the horizon for lung cancer patients and they are showing interesting differences between men and women. "A class of drugs known as epidermal growth factor receptor tyrosine kinase inhibitors seem to work better in women," Vidaver said. By contrast, a drug called bevacizumab, which is a recombinant humanized antibody to vascular endothelial growth factor and marketed under the trade name Avastin, appears to work better in men.
Paclitaxel poliglumex, a biologically-enhanced chemotherapeutic agent, which is being developed under the trade name Xyotax, has shown promise in pre-clinical and clinical trials, specifically for women. Research studies indicate that the metabolism of Xyotax by lung cancer cells may be influenced by estrogen and may work better than standard therapies, especially for women with pre-menopausal levels of the hormone.
Much more information is needed to help guide research about sex-specific treatments in the future. Recently, the Society for Women's Health Research, a Washington D.C., based advocacy organization, pledged to aid the Food and Drug Administration's Critical Path Initiative in its efforts to promote medical research on sex differences and encourage the development of sex-specific therapies.
"Advancing research into the biological basis of differences in the prevention, diagnosis, and treatment of disease in women and men is a significant part of the mission of the Society," said Phyllis Greenberger, M.S.W., president and CEO of the Society. "We know that there are sex differences in the processes of drug absorption and metabolism, and in some areas of safety and efficacy, so we owe it to all patients to further explore these differences in current and future therapies."