Outcomes after cancer diagnosis in children and adult patients with congenital heart disease in Sweden: a registry-based cohort study.

OBJECTIVE:Patients with congenital heart disease (CHD) have an increased cancer risk. The aim of this study was to determine cancer-related mortality in CHD patients compared with non-CHD controls, compare ages at cancer diagnosis and death, and explore the most fatal cancer diagnoses. DESIGN:Registry-based cohort study. SETTING AND PARTICIPANTS:CHD patients born between 1970 and 2017 were identified using Swedish Health Registers. Each was matched by birth year and sex with 10 non-CHD controls. Included were those born in Sweden with a cancer diagnosis. RESULTS:Cancer developed in 758 out of 67814 CHD patients (1.1%), with 139 deaths (18.3%)-of which 41 deaths occurred in patients with genetic syndromes. Cancer was the cause of death in 71.9% of cases. Across all CHD patients, cancer accounted for 1.8% of deaths. Excluding patients with genetic syndromes and transplant recipients, mortality risk between CHD patients with cancer and controls showed no significant difference (adjusted HR 1.17; 95% CI 0.93 to 1.49). CHD patients had a lower median age at cancer diagnosis-13.0 years (IQR 2.9-30.0) in CHD versus 24.6 years (IQR 8.6-35.1) in controls. Median age at death was 15.1 years (IQR 3.6-30.7) in CHD patients versus 18.5 years (IQR 6.1-32.7) in controls. The top three fatal cancer diagnoses were ill-defined, secondary and unspecified, eye and central nervous system tumours and haematological malignancies. CONCLUSIONS:Cancer-related deaths constituted 1.8% of all mortalities across all CHD patients. Among CHD patients with cancer, 18.3% died, with cancer being the cause in 71.9% of cases. Although CHD patients have an increased cancer risk, their mortality risk post-diagnosis does not significantly differ from non-CHD patients after adjustements and exclusion of patients with genetic syndromes and transplant recipients. However, CHD patients with genetic syndromes and concurrent cancer appear to be a vulnerable group.