The interaction of sex, age and ethnicity has a significant impact on overall survival in metastatic colorectal cancer patients, a study led by researchers at USC and the USC/Norris Comprehensive Cancer Center suggests.

While age and ethnicity are well-established factors that impact survival of colorectal cancer, the study found that gender also plays an important role in overall survival, said Andrew Hendifar, a fellow in the division of hematology/oncology at the Keck School of Medicine of USC and lead author of the study.

Researchers found that pre-menopausal women with metastatic colorectal cancer (18-44 years old) lived longer than younger men, while older women (75 and older) had significantly worse overall survival than older men.

The results of the study were presented at a poster discussion June 1 at the annual meeting of the American Society of Clinical Oncology held in Chicago.

The study adds to the growing evidence that female hormones are protective for colon cancer, researchers said.

“This study provides further evidence that estrogen may play an important role not only in colon cancer development but also progression of the disease and may impact how we develop therapies for women and men with colon cancer,” said Heinz-Josef Lenz, professor of medicine at the Keck School and a senior investigator on the study.

Researchers screened 56,598 patients with metastatic colorectal cancer from 1988 to 2003, using the Surveillance, Epidemiology and End Results registry.

Independent of age, there were no survival differences between men and women with metastatic colorectal cancer. However, when age was added to the model, sex became significantly associated with survival across all ethnicities.

Researchers also found that certain ethnicities had better overall survival than others. Namely, Hispanics and Asians have better outcomes than Caucasians and African Americans. Further studies in this area should look at how certain diets or specific surroundings contribute to the development of colorectal cancer, Hendifar noted.

“The data warrant further studies to determine the role of estrogen and ethnicity in colorectal cancer development,” he said. “In the future, we may tailor different treatments for men and women.”

The study was funded by grants in honor of Sharon A. Carpenter and from the Dhont Family Foundation.