Background
The risk of cardiovascular events in patients treated for colorectal cancer is debated due to diverging results in previous studies. Colorectal cancer and cardiovascular disease share several risk factors such as physical inactivity, obesity, and smoking. Information about confounding covariates and follow-up time are therefore essential to address the issue. This study aims to investigate the risk of new-onset cardiovascular events for patients with stage I-III colorectal cancer receiving elective surgery compared to a matched population.

Material and Methods
Using a prospective cohort, we compared cardiovascular events among 876 patients treated with elective surgery for incident stage I-III colorectal cancer diagnosed between January 1st, 2001 and December 31st, 2016 to a cancer-free cohort matched by age, sex, and time since enrollment (N = 3504). Regression analyses were adjusted for lifestyle, cardiovascular risk factors, and comorbidity. Multivariable analyses were used to identify risk factors associated with cardiovascular events in the postoperative (<90 days of elective surgery) and long-term phase (>90 days after elective surgery).

Results
After a median follow-up of 3.9 years, the hazard ratio (HR) for incident heart failure was 1.53 (95% CI 1.02–2.28) among patients operated for colorectal cancer. The postoperative risk of myocardial infarction or angina pectoris was associated with the use of lipid-lowering drugs. Long-term risks of cardiovascular events were ASA-score of III+IV and lipid-lowering drugs with HRs ranging from 2.20 to 15.8. Further, the use of antihypertensive drugs was associated with an HR of 2.09 (95% CI 1.06–4.13) for angina pectoris or acute myocardial infarction. Heart failure was associated with being overweight, diabetes, and anastomosis leakage.

Conclusion
We observed an increased hazard of heart failure in patients operated on for stage I-III colorectal cancer compared to cancer-free comparisons. We identified several potential risk factors for cardiovascular events within and beyond 90 days of elective surgery.