Marital status and colon cancer outcomes in US Surveillance, Epidemiology and End Results registries: does marriage affect cancer survival by gender and stage?

BACKGROUND: Marital status has been associated with outcomes in several cancer sites including breast cancer in the literature, but little is known about colon cancer, the fourth most common cancer in the US.
METHODS: A total of 127,753 patients with colon cancer were identified who were diagnosed between 1992 and 2006 in the US Surveillance, Epidemiology and End Results (SEER) Program. Marital status consisted of married, single, separated/divorced and widowed. Chi-square tests were used to examine the association between marital status and other variables. The Kaplan-Meier method was used to estimate survival curves. Cox proportional hazards models were fit to estimate the effect of marital status on survival.
RESULTS: Married patients were more likely to be diagnosed at an earlier stage (and for men also at an older age) compared with single and separated/divorced patients, and more likely to receive surgical treatment than all other marital groups (all p<0.0001). The five-year survival rate for the single was six percentage points lower than the married for both men and women. After controlling for age, race, cancer stage and surgery receipt, married patients had a significantly lower risk of death from cancer (for men, HR: 0.86, CI: 0.82-0.90; for women, HR: 0.87, CI: 0.83-0.91) compared with the single. Within the same cancer stage, the survival differences between the single and the married were strongest for localized and regional stages, which had overall middle-range survival rates compared to in situ or distant stage so that support from marriage could make a big difference.
CONCLUSIONS: Marriage was associated with better outcomes of colon cancer for both men and women, and being single was associated with lower survival rate from colon cancer.