Cancer Mortality Higher in Men

Men are more likely than women to die of cancer in the U.S., a new study shows.

"Our research suggests that the main factor driving greater frequency of cancer deaths in men is the greater frequency of cancer diagnosis, rather than poorer survival once the cancer occurs," says study researcher Michael B. Cook, PhD, BsC, of the National Cancer Institute.

The study is published in Cancer Epidemiology, Biomarkers & Prevention.

Cook says that if investigators "can identify the causes of these gender differences in cancer incidence, then we can take preventative actions to reduce the cancer burden in both men and women.

Cook and his research team analyzed U.S. data from a large database that contained statistics on 36 cancers by age and sex for the period of 1977 to 2006.

For "the vast majority" of the cancers, rates were higher among men than women, the researchers write.

The highest male-to-female death rate ratios were 5.51 men for every woman for lip cancer, 5.37 to 1 for cancer of the larynx, and 4.47 to 1 for cancer of the hypopharynx (a type of throat cancer).

The male-female death rate ratio for cancer of the esophagus was 4.08 to 1, and 3.36 to 1 for urinary bladder cancer.

Many cancers with the highest overall death rates also showed greater death risk for men than women. The male-female ratios for lung cancer were 2.31 to 1, for colorectal cancer 1.42 to 1, and 1.37 to 1 for pancreatic cancer.

For leukemia, the male-female ratio was 1.75 to 1, and for liver and intrahepatic bile duct cancer the ratio was 2.23 to 1.

The risk of cancer is known to be considerably higher in men, with potential contributory factors including hormones, susceptibility, viral infections, tobacco exposure, and healthcare utilization.

But less is known about possible gender differences in mortality rates and cancer-specific five-year survival.

"These are important questions because disparities in cancer mortality result from the combined effects of incidence and survival; if sex differences exist in cancer mortality and are the result of sex differences in cancer incidence, and not cancer survival, then such evidence may suggest etiologic clues for future analytic studies," the NCI researchers explained.

To explore this, they analyzed data from the Surveillance Epidemiology and End Results database and the National Center for Health Statistics for the periods 1977 to 2006, 1977 to 1986, 1987 to 1996, and 1997 to 2006.

Other cancers they identified as having high male-to-female mortality rate ratios included those of the:

Tonsils, 3.28 (95% CI 3.17 to 3.39)

Oropharynx, 3.05 (95% CI 2.95 to 3.16)

Floor of the mouth, 2.89 (95% CI 2.77 to 3.03)

Tongue, 2.53 (95% CI 2.49 to 2.58)

Nasopharynx, 2.47 (95% CI 2.40 to 2.55)

The only cancers found to have higher mortality rate ratios for women were those of the peritoneum, omentum, and mesentery (0.39), gall bladder (0.56), and anus (0.78).

The researchers found that there had been some changes over time, such as decreases in the male-to-female ratios in lung, laryngeal, and pancreatic cancers but increases in esophageal, skin, and hepatic cancers.

They also found changes in mortality by age.

For example, the male-to-female mortality rate ratio for esophageal cancer has been increasing for patients ages 40 to 69, largely because of a decrease in mortality among women.

For skin cancer, the male-to-female mortality ratio has increased in patients 50 and older, because mortality has increased in men but remained stable in women.

Using Cox proportional hazards models, Cook's team then analyzed five-year survival, and again found worse survival for men in many cancers:

Skin other than basal and squamous cell, HR 1.58 (95% CI 1.52 to 1.64)

Endocrine, HR 1.32 (95% CI 1.24 to 1.42)

Floor of the mouth, HR 1.32 (95% CI 1.07 to 1.63)

However, adjustment for tumor grade and stage attenuated some of the excess hazards for men.

An example was cancer of the tongue, where the hazard ratio fell from 1.07 to 0.89 after adjustment.

Possible reasons for sex differences in survival could include environmental exposures, according to the researchers.

The researchers noted that in previous work, they had found that the incidence of cancer was higher among men, which was similar to the mortality findings in this study.

"This supports the idea that sex disparities in cancer mortality arise from the sex differences in cancer incidence," they stated.

However, the differences in survival could relate to men having a longer lead time before diagnosis, typically presenting with later stage and more aggressive tumors.

Women tend to take greater advantage of the available healthcare services, the researchers explained.

A strength of the study was the large cancer registry, while a limitation was the possibility of errors in causes of death listed on the death certificate.

Moreover, there was no information on potentially confounding factors such as comorbidities.

The NCI researchers concluded that future studies should examine the etiologic factors contributing to the higher incidence rates among men.