Abstract
Risk of colorectal cancer (CRC) is considerably higher in men compared to women; however, there is inconclusive evidence of sex differences in CRC prognosis. We aimed to assess and explain sex differences in 5-year relative survival using standard and model-based period analysis among 164,996 patients diagnosed with CRC from 1997 to 2006 and reported to 11 German cancer registries covering a population of 33 million inhabitants. Age-adjusted 5-year relative survival was higher in women (64.5% vs. 61.9%, P<0.0001). A substantial survival advantage of women was confirmed in multivariate analysis after adjusting for CRC stage and subsite in subjects under 65 years of age (relative excess risk, RER 0.86, 95% CI 0.82–0.90), but not in older subjects (RER 1.01, 95% CI 0.98–1.04); this pattern was similar in the 1st and in the 2nd to 5th year after diagnosis. The survival advantage of women varied by CRC stage and age and was most pronounced for localized disease (RERs 0.59–0.88 in various age subgroups) and in patients under 45 years of age (RERs 0.59, 0.72 and 0.76 in patients with localized, regional or advanced disease, respectively). On the contrary, sex differences in survival did not vary by location of CRC. In conclusion, our large population-based study confirmed a survival advantage of female compared to male CRC patients, most notably in young and middle aged patients and patients with localized disease. The effect of sex hormones, either endogenous or through hormonal replacement therapy, might be the most plausible explanation for the observed patterns.
Highlights
Colorectal cancer (CRC) is the third most common cancer and the fourth most common cancer cause of death, accounting for more than 600,000 deaths per year globally [1]
After exclusion of 27,076 death certificate only (DCO) notifications (14.1%), records of 164,996 CRC patients from 11 German cancer registries were retained for analysis
The multivariate model showed similar patterns of age-specific survival advantages for female patients across CRC subsites, suggesting independence of disease localization of survival advantages of women (P-value for interaction term 0.12). This is to date the largest study focusing on sex differences in CRC survival and the first one utilizing multivariate population-based relative survival analysis including CRC stage and disease subsite
Summary
Colorectal cancer (CRC) is the third most common cancer and the fourth most common cancer cause of death, accounting for more than 600,000 deaths per year globally [1]. Incidence and mortality rates are considerably higher in men than in women [2]. Several studies reported superior survival in females [3,4,5]; other studies did not report any difference [6]. Two recent studies examined potential variation of sex differences in survival of CRC patients by age. Whereas younger women exhibited better survival than younger men, an opposite pattern was seen among older patients [7,8]. As the age cut off (around 50 years) was chosen as a surrogate for natural menopause, it was hypothesized that the survival advantage of female patients at younger age could be partially explained by favourable effect of endogenous female sex hormones
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