Sex differences in the impact of multimorbidity on long-term mortality for patients with colorectal cancer: a population registry-based cohort study.

Background: Women have better survival than men patients with colorectal cancer (CRC), but the extent to which this is due to multimorbidity is unclear.

Methods: A population-based study of 1843 patients diagnosed with CRC in Australia. Data included patient's demographics, multimorbidity, tumour histology, cancer stage, and treatment. We estimated the risks of all-cause mortality and cause-specific mortality due to cancer or non-cancer causes.

Results: Men had lower survival than women (P ≤ 0.010) amongst those diagnosed at Stages I-III (15-year survival: 56.0% vs 68.0%, 48.5% vs 60.7%, 34.8% vs 47.5%, respectively), excepting Stage IV (14.4% vs 12.6%; P = 0.18). Married men exhibit better survival than those who were never married (P = 0.006). Heart attacks (9.9% vs 4.3%, P < 0.001) and emphysema (4.8% vs 2.1%, P = 0.004) were more prevalent in men than women. Comorbid stroke and high cholesterol (adjusted hazard ratio, AHR = 2.22, 95% confidence interval, CI = 1.17-4.21, P = 0.014) and leukaemia (AHR = 6.36, 95% CI = 3.08-13.1, P < 0.001) increased the risk of cancer death for men only. For women, diabetes increased the risk of all-cause death (AHR = 1.38, 95% CI = 1.02-1.86, P = 0.039) and high blood pressure increased the risk of death due to non-cancer causes (AHR = 2.00, 95% CI = 1.36-2.94, P < 0.001).

Conclusion: Separate models of CRC care are needed for men and women with consideration of multimorbidity and social factors.