Study co-author Sven Wilson, a professor at Brigham Young University, and Li Wang of Pennsylvania State College of Medicine and colleagues say the findings are based on analysis of 127,753 patient records.
The researchers found married people were diagnosed at earlier stages of colon cancer and sought more aggressive treatment.
"Controlling for the stage that the cancer was detected is key," Wilson says in a statement. "Without that, it's hard to know whether the analysis is just picking up a diagnosis effect."
Marriage is a self-selected group, and Wilson says the selection process makes it difficult to sort out the root cause, but he speculates spouses serve as an important informal caregiver during a critical time, and that extra support may translate into better disease management and better outcomes.
The study is published online ahead of print in the journal Cancer Epidemiology.