After diagnosis, women are more likely overall to survive cancer than men, but the reasons for this have been unclear. While scientists have long known gender to be an important factor in the way disease originates and develops, is diagnosed, and what a person’s likely outcome will be, until now, no one has examined why the risk of malignancy is higher in men than women in a majority of specific cancer types.
Is it because of hormone or body mass differences between the sexes? Do men have higher exposure to cancer-causing substances than women, or are they just more susceptible to harmful carcinogenic effects or viral infections that can lead to cancer? Are women more likely to seek medical care than men? Or is it a complex set of some or all of these factors, and can social and clinical changes be made to affect better outcomes for men, as well as women?
Michael B. Cook, Ph.D., an investigator in the division of cancer epidemiology and genetics at the National Cancer Institute, and colleagues set out to answer these important questions by piecing together clues about 36 specific cancers. The results were published early online, in the August 2011 print edition of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
Cook and his colleagues used U.S. vital rates and survival data between 1977-2006 from the Surveillance Epidemiology End Results (SEER) database for specific cancers by sex and age. They assessed whether cancer mortality rates and cancer survival differed by sex.
In their analysis of five-year cancer survival, the researchers adjusted for age, year of diagnosis and tumor stage and grade, when this information was available. Cook and his team found that a person’s sex did not play a major role in cancer survival.
For many cancers, men have poorer survival than women but the differences are slight. It is difficult to assign any singular root cause, according to the study, but influences include differences in behavior of the individual tumor, people without symptoms getting cancer screening, presence of other illnesses and how often the person gets regular medical care.