Scientists from the University of California at San Francisco have released a study that sheds new light on colon cancer and the likelihood of survival following a diagnosis. According to a report from the Washington Post, the study found that people with tumors on the left side of their colon have a significantly higher chance of surviving than those with tumors on the right side of their colon.

The study, published on Wednesday, was funded by the National Institutes of Health. Researchers found that of 1,100 colon cancer patients, people with tumors on the left side of the colon survived for a median of 33.3 months, while people with tumors on the right side of the colon survived for a median of just 19.4 months.

The findings surprised lead author Alan Venook, a professor of medicine at UCSF. He said that previous research has suggested a link between the location of a colon tumor and a patient’s chance of survival, but the recent study reveals that the association may be stronger than previously thought.

The study offers new insights into which treatments for colon cancer may be more effective for different patients. Two treatments were tested in the study in combination with chemotherapy. The study found that the drug Avastin was more effective in patients with right-side tumors, while the drug Erbitux was more effective for patients with left-side tumors.

While the data in the study painted a stark picture surrounding tumor location, scientists are still in the dark as to the underlying biological mechanisms affecting survival length. Venook says it may have something to do with the fact that the left and right sides of the colon are generated from different embryonic tissues, and thus have different properties.

A news release from the University of California at San Francisco describing the details of the study can be found here.