TUESDAY, July 12 (HealthDay News) -- Men in the United States are much more likely than women to die of cancer, a new report from the U.S. National Cancer Institute found.

Gender differences in cancer incidence -- more men than women develop cancer in the first place -- rather than differences in cancer survival appeared to drive the findings, the researchers said.

"If we can identify modifiable causes of sex difference in cancer incidence and mortality then preventative actions could reduce the cancer burden in both men and women," said lead researcher Michael B. Cook, a National Cancer Institute epidemiologist.

Cook said that for many cancers, male and female incidence rates, and by extension death rates, have changed disproportionately over time.

This is likely because of differences in "carcinogenic exposures, metabolism and susceptibility," he said. Increased rates of smoking among men, and differences in infections, hormones and contact with toxic metals may all come into play, he said.

In terms of survival, however, the gender gap was minimal, the researchers found.

The study is published in the August issue of Cancer Epidemiology, Biomarkers & Prevention.

To look for gender differences in cancer deaths and survival rates, Cook's team used information from the NCI's Surveillance, Epidemiology and End Results database, which includes information on survival and deaths for 36 different cancers.

Lip cancer, for example, killed 5.51 men for every 1 woman. Larynx cancer claimed the lives of 5.37 men for every 1 woman; throat cancer, 4.47 men for each woman; and urinary bladder cancer, 3.36 men per 1 woman.

Examining cancers with the highest death rates overall, the researchers again found higher mortality among men than women. For example, lung and bronchus cancer killed 2.31 men for every 1 woman. Liver cancer killed 2.23 men for every woman; colon and rectum cancer took 1.42 males' lives for every woman; pancreatic cancer, 1.37 men for each woman; and leukemia, 1.75 men for every woman.

The research team found that gender was not a major factor in five-year survival when age, year of diagnosis and tumor stage were taken into account.

"But, for certain cancers we did observe slight sex differences in survival," Cook said, adding it is difficult to assign any root cause to that observation.

"This is not really a novel finding," said Rebecca Siegel, an epidemiologist at the American Cancer Society, commenting on the study. "We know that men have a higher risk of developing and dying from cancer for a variety of reasons, and some reasons which we don't fully understand," she added.

"The fact they didn't find large differences in survival is comforting," she said.

The death rates reflect different smoking and drinking patterns, Siegel pointed out. Also, cancers related to work exposures are more common among men, she noted.

Because smoking among women peaked in the 1970s and 1980s, Siegel said she expects to see the gender difference in cancer deaths start to narrow.

Men may get diagnosed later than women because they tend to see their doctors less often, and this could affect mortality rates, Siegel also suggested.

Future studies should explore the factors responsible for the disparity, the study authors said.

More information

For more information on cancer, visit the American Cancer Society.