Childhood cancer survival rates in the UK have improved significantly, exceeding 84% for children diagnosed before age 15. However, these broad statistics mask heterogeneity in outcomes, with evidence suggesting social gradients in survival across various child health conditions. Studies have shown socioeconomic inequalities in adult cancer survival, with those from deprived areas experiencing poorer outcomes. Similar trends have been observed in childhood leukemia, where children from deprived backgrounds face a higher risk of death. A limited number of UK studies have explored ethnic differences in childhood cancer survival, revealing increased risks for South Asian children diagnosed with certain cancers. Although ethnicity and socioeconomic status are recognized as important determinants of long-term survival, most studies have not analyzed temporal changes. National estimates of these inequalities over extended periods are lacking. Yorkshire, with its diverse urban and rural communities and a significant South Asian population (primarily of Mirpur, Pakistan origin), provides a unique setting to examine these disparities. This study aims to utilize high-quality population-based data on children (aged 0-14) diagnosed with cancer between 1997 and 2016 to explore patterns of socio-economic and ethnic variations in survival outcomes over time in a regional pediatric cancer population. The study's focus on a defined geographical area with a relatively homogenous South Asian population allows for detailed analysis of long term survival trends.

Previous research has demonstrated improvements in childhood cancer survival rates in the UK, but these improvements have not been equally distributed across all subgroups. Studies have consistently shown socioeconomic inequalities in various health outcomes, including asthma, mental illness, and adiposity in children. In the adult cancer population, socioeconomic disparities in cancer survival have been well documented. Research on childhood leukemia specifically highlighted the increased risk of death for children from more deprived backgrounds. A limited number of studies have examined ethnic variations in childhood cancer survival outcomes, primarily focusing on acute lymphoblastic leukemia (ALL) and lymphoma. These studies found increased relative risks of death for South Asian children compared to White children. Overall, despite growing evidence suggesting the impact of ethnicity and socioeconomic status on paediatric cancer survival, systematic national-level data illustrating temporal changes in these inequalities remain largely absent. This lack of longitudinal data limits the understanding of how these disparities have evolved over time and hinders the development of targeted interventions.

This population-based study used data from the Yorkshire Specialist Register of Cancer in Children and Young People (YSRCCYP), a regional database containing detailed information on children diagnosed with cancer since 1974. The study included 2674 children (aged 0-14) diagnosed with malignancy or borderline/benign CNS tumors between 1997 and 2016. Diagnoses were categorized into four groups: leukemia, lymphoma, CNS tumors, and other solid cancers. Patients were followed up until December 31, 2020, with minimal loss to follow-up. Ethnicity was assigned using linked hospital episode statistics data, with Onomap naming algorithms used for missing data. Townsend deprivation index was used to measure area-based material deprivation, categorized into population-weighted fifths. Kaplan-Meier estimation was used to describe survival trends over time, stratified by ethnic group and deprivation. Cox regression models were used to quantify the joint effect of ethnicity and deprivation on mortality risk, adjusting for confounders such as sex, age, relapse, cancer subtype, stage, and treatment. Imputation methods were used to handle missing stage data. The study used causal inference methods to interpret the deprivation coefficient and address potential confounding between ethnicity and deprivation.

The study found a clear social gradient in five-year survival for children diagnosed with leukemia between 1997 and 2006, with higher survival among those in the least deprived fifth. South Asian children diagnosed with leukemia during this period had a 15% lower survival rate than non-South Asian children. However, survival estimates improved significantly for South Asian children, resulting in converging survival rates by 2016. In contrast, lymphoma survival showed widening disparities across the study period, with South Asian children experiencing a 15% lower five-year survival rate compared to non-South Asian children. CNS tumor survival also demonstrated persistent socio-economic disparities, particularly until 2012. Other solid tumors showed initial higher survival rates for South Asian children (1997-2006) which subsequently reduced over time, with only a minor difference remaining in 2007-2016. Cox regression analysis for all cancers combined revealed a significant association between increased deprivation and increased mortality risk (1997-2001). For leukemia, a higher deprivation level was associated with increased death risk before 2002, but this association diminished after 2002. For CNS tumors, socioeconomic disparities in survival persisted until 2011, but were reduced for diagnosis after 2012. Other solid tumors showed persistent socio-economic differences in mortality risk.

This study provides valuable insights into the complex interplay between socioeconomic status, ethnicity, and childhood cancer survival in the UK. The findings highlight the ongoing challenge of health inequities despite universal healthcare access. The observed disparities in survival across different cancer types suggest the need for a nuanced approach to interventions, considering the specific risk factors and mechanisms driving inequalities in each type of cancer. The significant improvements observed in overall survival for South Asian children and those living in the most deprived areas, coupled with a reduction in some disparity trends, suggest the potential success of policies and interventions aimed at improving access to healthcare and addressing socioeconomic determinants of health. Further research is needed to pinpoint the exact factors contributing to these disparities. The substantial improvements in the survival of South Asian children suggest potential genetic factors influencing treatment response. This warrants further investigation through genomics studies. The persistent disparities in CNS tumors and lymphoma highlight the need for focused interventions aimed at addressing these specific issues.

This study demonstrates the persistent existence of socio-economic and ethnic inequalities in childhood cancer survival within the UK's universal healthcare system. The observed disparities vary across cancer types, indicating a need for targeted interventions. While improvements have occurred, particularly for South Asian children with leukemia, significant challenges remain, notably in lymphoma and CNS tumors. Further research, including genomic studies and exploration of other socioeconomic factors, is essential to understand the underlying causes and develop effective strategies to achieve equitable outcomes for all children diagnosed with cancer.

The relatively small number of South Asian children in the study might limit statistical power and the ability to perform detailed subgroup analyses. The reliance on area-level deprivation indicators may not fully capture individual-level socioeconomic factors. Missing staging data for a significant proportion of cases necessitated imputation, introducing potential bias. The study's regional focus might not be generalizable to other areas with different demographic characteristics. The use of a binary ethnic classification limits the granularity of analysis.