Background: A gender difference in survival has been documented in colorectal cancer (CRC) patients, although the underlying mechanism remains undefined. This study aimed to gain improved insight into this difference, with a special focus on improved cancer-specific survival.
Methods: The study population consisted of 82,402 patients with invasive CRC who had undergone surgery in Japan between 1985 and 2004. To estimate improved survival, multivariate adjustment using patient demographics and tumor characteristics was performed.
Results: Patient characteristics changed over time. The 5-year survival rates increased from 66.5 to 76.3 % during the study period. Higher survival rates persisted in women over time (multivariate-adjustment model-hazard ratio [HR] 0.87, 95 % confidence interval [CI] 0.85-0.90). Patients who received surgery during the period 2000-2004 had significantly longer survival than those during the period 1985-1989 (men: HR 0.70, 95 % CI 0.67-0.74; women: HR 0.72, 95 % CI 0.67-0.76). However, there was no gender difference regarding improved survival.
Conclusions: A reduced risk of cancer-specific death for women relative to men persisted over time; however, enhancement of survival was equally observed in both genders. Identification of factors associated with gender differences and changes over time in CRC survival may serve as targets for further improvement.
Keywords: Cancer specific survival; Colorectal cancer; Gender differences; Improvement in survival.