NCI Study Finds Men Have Higher Cancer Mortality Rates than Women

A recent NCI study has shown that men have higher cancer mortality rates than do women. The study systematically extracted data from the Surveillance, Epidemiology, and End Results (SEER) Database of the NCI, analyzing 29 years of survival statistics data (ending in 2006) from 36 different cancers across the United States.  The results are published in Cancer Epidemiology, Biomarkers & Prevention, an AACR journal (doi: 10.1158/1055-9965.EPI-11-0246). 

“Men are more likely to die from cancer than women,” said Michael Cook, PhD, an investigator at the NIC   “We found this to be true for a majority of specific types of cancer.”

The authors emphasize that it is hard to specify the cause for the disparity. However, potential differences may be tumor growth kinetics, tumor behavior (including metastasis behavior), and concurrent illnesses. Additionally, patterns of seeking healthcare, including delayed diagnosis and diagnosis at later disease stages may contribute to the trend. The authors point out that over-diagnosis via screening can affect sex-specific cancer survival proportions. Asymptomatic cancers may be treated more frequently in females compared to males, leading to better cancer outcomes. This rationale is supported by the observation that women are more readily diagnosed with earlier stage and less aggressive cancers compared to their male counterparts. This may be part of the healthcare-seeking issue; women exploit early screening resources.

The patterns of sex-specific mortality rates were very similar to the patterns of observed cancer incidence rates. Cancer incidence rates had previously been reported by the same investigator (Cook et al. Cancer Epidemiol Biomarkers Prev 2009;18:1174–82), which discuss issues relating to sex disparities in cancer incidence.

“Our research suggests that the main factor driving the greater frequency of cancer deaths in men is the greater frequency of cancer diagnosis, rather than poorer survival once the cancer occurs,” said Cook. “If we 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.”

Result Details
The study found that lip cancer (where 5.51 men died compared to 1 female), larynx (5.37-to-1);, hypopharynx 4.47-to-1), espophagus 4.08-to-1), and urinary bladder cancers (3.36-to-1) had the highest male/female mortality ratios. 

Cancers that have the greater risk of death overall also showed the slight disparity of greater risk of death in men compared to women. These included lung and bronchus cancer (2.31-to-1), colon and rectum (1.42-to-1), pancreas (1.37-to-1), leukemia (1.75-to-1), and liver and intrahepatic bile duct (2.23-to-1).

The disparity for lung cancer is highlighted by the authors as potentially having to do with estrogen receptor b, which is expressed in lung cancer cells.

Future Directions
The cause of the disparity in mortality is difficult to address, but both prospective and retrospective analysis of quality data will help to address whether early screening, different patterns of seeking and receiving healthcare, and other factors have a causal relationship to the results reported in this study. Follow-up studies should rely on accurate and robust data on concomitant morbidities, cause of death, and accurate diagnoses. With better record-keeping, observational studies such as this one can help to decipher cancer causes, better screening processes, and ways to prevent cancer.