# Risk of Childhood Cancer in Children with Congenital Anomalies and Their Impact on Survival: A Population-Based Registry Approach

## TL;DR

Children with congenital anomalies have a 5-fold higher risk of developing cancer and worse survival when they have both cancer and anomalies.

## Contribution

This study confirms a strong cancer risk in children with congenital anomalies and highlights the need for clinical follow-up.

## Key findings

- Children with congenital anomalies had a 5.5-fold increased cancer risk compared to the general population.
- Genetic disorder anomalies and Down syndrome showed the highest cancer risk (SIR = 26.6 and 22.2, respectively).
- Children with both cancer and congenital anomalies had worse 5-year survival than those with only one condition.

## Abstract

Childhood cancers and congenital anomalies are rare diseases, but a major cause of death among children. An increased risk of developing cancer in children with congenital anomalies was reported. We evaluated this risk and their impact on survival. The data were obtained from two population-based registries established in the Valencian Region: the Childhood and Adolescent Cancer Registry and the Congenital Anomalies Registry. The study population was children with major congenital anomalies and/or childhood cancers, born between 2007 and 2020. Our study confirmed an increased cancer risk 5-fold in children with congenital anomalies compared with children without this pathology. The highest risk was observed for children with genetic disorder anomalies and children with Down syndrome. In addition, children having childhood cancers and congenital anomalies had worse survival compared with children with only one of these diseases. These results pointed out the need for clinical follow-up after congenital anomaly diagnosis.

An increased cancer risk in children with congenital anomalies was reported. This study explored the cancer risk in children aged 0–14 diagnosed with major congenital anomalies during the first year of life, born in 2007–2020 and residing in the Valencian Region, as well as their impact on survival. The Childhood and Adolescent population-based Cancer Registry provided the cancers diagnosed in the period 2007–2020 in children born between 2007 and 2020. They were linked with data from the Congenital Anomalies population-based Registry to identify children with congenital anomalies. Standardized incidence ratio (SIR) and 95% confidence intervals (95% CI) were computed. Kaplan–Meier analysis was used to estimate survival function. Children with congenital anomalies had 5-fold cancer risk compared with the reference population (SIR = 5.5; 95% CI: 4.3–7.0). The highest risk was found for children with genetic disorder anomalies (SIR = 26.6; 95% CI: 17.3–37.8) and children with Down syndrome (SIR = 22.2; 95% CI: 10.1–39.1). Children with cancers and congenital anomalies had worse 5-year survival compared with children having only one of these diseases. These results point out the need to clinical follow-up after congenital anomaly diagnosis. The low number of cases, due to rarity of the childhood cancers and congenital anomalies, was the main limitation of performing more detailed analyses.