Objective: Accumulating evidences showed some positive relations between myocardial infarction (MI) and new onset cancer. We aim to investigate whether MI is associated with an increased risk of incident cancer.
Methods: A comprehensive literature list was identified from MEDLINE, Embase, and Web of Science databases from inception until October 2018. The main inclusion criteria included observational studies investigating the association between MI and new onset cancer. Stata 12.0 software was used for meta-analysis.
Results: Of 862 potentially relevant studies, five cohort studies met all inclusion criteria. The pooled cancer incidence rate was 9.5% (95% CI=8.3–10.7%). Pooled analysis of OR showed that the increased overall cancer risk in MI patients in comparison with controls had no statistical significance (OR=1.08; 95% CI=0.97–1.19, P=0.153). Subgroup analysis by gender demonstrated that the overall cancer risk was only significantly increased in female (OR=1.10; 95% CI=1.01–1.20, P=0.025), but not in male patients (OR=1.04; 95% CI=0.99–1.10, P=0.124). In terms of cancer type, the increased cancer risk was only significant for lung cancer (male OR=1.12; 95% CI=1.05–1.19, P<0.01; and female OR=1.51; 95% CI=1.15–1.99, P<0.01), but not for prostate (OR=0.96; 95% CI=0.85–1.09, P=0.546) or breast cancer (OR=0.94; 95% CI=0.86–1.04, P=0.222). In addition, the increased cancer risk was only significant in the first 6 months (OR=1.93; 95% CI=1.42–2.63, P<0.01) but not in 6 months–1-year (OR=1.03; 95% CI=0.92–1.15, P=0.627) or >1-year (OR=0.98; 95% CI=0.93–1.04, P=0.585) follow-up after MI.
Conclusion: From available evidence, the increased overall cancer risk after MI was only significant in female but not in male patients. Besides, the increased cancer risk could be driven by increased short-term cancer incidence after MI and certain cancer types such as lung cancer.


Keywords: myocardial infarction, incident cancer, meta-analysis


INTRODUCTION

Myocardial infarction (MI) and cancer are two leading causes of morbidity and mortality worldwide. With the development of pharmacotherapy and timely cardiac revascularization, in past decades, the prognosis of MI has been fundamentally improved with higher survival rate.1 Recently, some studies have suggested cardiovascular diseases including MI and cancer share a number of risk factors and possess various similarities.2,3 Inflammation, oxidative stress, obesity, and smoking are all contributors to the occurrence of MI and cancer.4–7 Some observational studies also found noncardiac causes (mainly malignancies and chronic diseases) are responsible for the majority of later deaths in MI patients treated with percutaneous coronary intervention.8,9 Thus, it is plausible to assume that patients with MI history are more likely to develop incident cancer.

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Meanwhile, in past years, several clinical and epidemiological studies have been done in this field and showed some positive associations between MI and new onset cancer.10,11 However, the results were inconsistent or even conflicting.12,13 In view of the high disease burden of MI and cancer, it is necessary to confirm whether MI is a new risk factor for incident cancer. Therefore, we conducted a systematic review and meta-analysis in accordance with the PRISMA guidelines and our predesigned protocol to clarify the association between MI and incident cancer.