# Childhood cancer in Sweden during the COVID-19 pandemic: Temporal patterns in incidence and survival in a nationwide register-based cohort study

## TL;DR

This study found that childhood cancer incidence and survival in Sweden remained stable during the pandemic, with no evidence of worse outcomes despite concerns about disruptions.

## Contribution

The study provides novel insights into the resilience of childhood cancer care in Sweden during the pandemic using nationwide registry data.

## Key findings

- Overall cancer incidence rates remained stable during the pandemic years (2020–2022) compared to pre-pandemic years (2015–2019).
- Some cancer types showed temporary fluctuations in incidence, but no increase in mortality or worse survival was observed.
- One-year survival improved slightly during the pandemic, suggesting care disruptions did not lead to poorer outcomes.

## Abstract

The COVID-19 pandemic raised concerns about diagnostic delays and treatment disruptions in childhood cancer, potentially threatening survival. We assessed childhood cancer incidence and survival in Sweden, where only few restrictions were implemented, during the pandemic period.

We conducted a nationwide, register-based cohort study including all children and adolescents (0–19 years) with a new cancer diagnosis, defined according to the International Classification of Childhood Cancer, Third Edition (ICCC-3), reported to the Swedish National Cancer Register during 2015–2022 (N = 3,333; 2,069 pre-pandemic and 1,264 during the pandemic). We compared quarter-specific age-standardized incidence rates (ASR) per 1,000,000 (overall and by diagnostic group) during 2020–2022 to the 2015–2019 average. Overall survival at 3, 6, and 12 months post-diagnosis was calculated using the Kaplan–Meier estimator, and mortality at the same intervals was assessed with logistic regression, adjusted for age at diagnosis, sex, and maternal education.

Overall incidence rates remained largely stable during the pandemic (ASR2015–2019: 179.5; 95% CI [172.9,186.1], ASR2020: 174.7; 95% CI [160.5,189.0], ASR2021: 176.5; 95% CI [161.6,191.5], ASR2022: 181.2; 95% CI [166.3,196.2]), but diagnostic groups showed differing tendencies. Acute lymphoblastic leukemia (ALL) declined from February 2020, followed by a rebound in 2021. Acute myeloid leukemia (AML) declined throughout 2020–2022 without evidence of a rebound. Lymphomas declined in mid-2020 before returning to pre-pandemic levels. Central nervous system (CNS) tumors transiently increased in 2020. Overall 1-year survival was 94.8% (95% CI [93.9,95.8]) in the pre-pandemic period and 95.9% (95% CI [94.8,97.0]) during the pandemic. No increase in 6-month or 1-year mortality was observed; if anything, point estimates suggested lower 1-year mortality for ALL (aOR = 0.37; 95% CI [0.08,1.21]; p = 0.14) and CNS tumors (aOR = 0.61; 95% CI [0.31,1.14]; p = 0.13). The main limitation of this study was statistical uncertainty for certain diagnostic groups due to small case numbers.

Overall childhood cancer incidence and survival in Sweden showed no major changes during the COVID-19 pandemic. Fluctuations in diagnostic-group-specific incidence may reflect delayed diagnoses or shifts in disease triggers; however, the timing of the ALL decline and the lack of AML rebound challenge this interpretation. Stable or improved survival suggests that any disruptions were not associated with poorer survival up to 1 year after diagnosis.

Childhood cancer requires timely diagnosis and uninterrupted treatment, and there have been concerns that the COVID-19 pandemic might have disrupted this care.

Reports from several countries have yielded heterogeneous findings about whether fewer children were diagnosed with cancer during the pandemic; research about survival during this period is particularly scarce.

Sweden kept schools and most of society open, offering a unique setting to examine patterns in childhood cancer incidence and survival during the pandemic.

We examined all cancers newly diagnosed in children and adolescents in Sweden from 2015 to 2022, using nationwide health registers (3,333 children and adolescents).

We compared the number of new diagnoses and survival up to one year after diagnosis during the pandemic years (2020–2022) with the pre-pandemic years (2015–2019).

Overall, childhood cancer diagnoses did not decrease during the pandemic.

Some cancers showed transient increases or decreases, but these changes were not accompanied by worse survival outcomes.

Childhood cancer care in Sweden likely remained resilient during the pandemic, as no evidence of poorer short-term survival was observed despite concerns about delays or disruptions.

Temporary changes in diagnoses of specific cancer types may reflect normal fluctuations rather than lasting pandemic-related shifts.

The findings highlight the value of strong, adaptable healthcare systems in protecting essential services during global crises.

Longer-term monitoring is needed to understand whether incidence patterns or outcomes change in the post-pandemic era.

Using national registry data, Christina-Evmorfia Kampitsi and colleagues examine patterns in childhood cancer incidence and survival before and during the COVID-19 pandemic in Sweden.