(B-004) Risk of Cancer in Patients with First-Time Seizure: A Population-Based Cohort Study

Monday, August 25, 2025

11:30 AM - 1:00 PM ET

Co-Author(s)

Andreas Lund Pedersen

Department of Clinical Epidemiology, Center for Population Medicine, Aarhus University Hospital and Aarhus University, Aarhus, Denmark, Denmark

Co-Author(s)

DK

Dóra Körmendiné Farkas

Department of Clinical Epidemiology, Center for Population Medicine, Aarhus University Hospital and Aarhus University, Aarhus, Denmark, Denmark
CH

Cecilia Hvitfeldt Fuglsang, MD, PhD

Department of Clinical Medicine, Department of Clinical Epidemiology, Aarhus University and Aarhus University Hospital, Denmark
VH

Victor W. Henderson

Departments of Epidemiology & Population Health and of Neurology & Neurological Sciences, Stanford University, Stanford, California, United States
SK

Sofie Kejlberg Al-Mashhadi, MD

PhD student
Department of Clinical Epidemiology, Center for Population Medicine, Aarhus University Hospital and Aarhus University, Denmark
HS

Henrik Toft Sørensen

Professor
Department of Clinical Epidemiology and Center for Population Medicine, Aarhus University, Aarhus, Denmark
AARHUS N, Denmark

Presenting Author(s)

HE

Holly Elser

Department of Neurology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA, United States

Background: Seizures may indicate serious underlying conditions, including brain tumors. However, their association with non-neurological cancers has been less extensively studied.

Objectives: To estimate the risk of cancer in patients with first-time seizures and compare the risk with that of the general population.

Methods: In a Danish nationwide population-based cohort study, we used the Danish medical and administrative registries, the Danish National Patient Registry, the Civil Registration System, and the Danish Cancer Registry, to identify all patients (N= 132,852) diagnosed with a first-time seizure during 1996–2022. The patients were followed until a cancer diagnosis, emigration, death, or end of data collection, whichever came first.
Risks of cancers were estimated using the Aalen Johansen method. Furthermore, we used Poisson regression to compute standardized incidence ratios (SIRs), with 95% confidence intervals (Cis), as the ratio of observed to expected number of cancers using national incidence rates as the reference. Both absolute risks and SIRs were calculated for the periods < 1 year and 1-20 years, respectively. Analyses were stratified by age (≤5 years and ≥6 years). Finally, the number of patients needed to be screened to find one excess cancer was computed.

Results: In individuals with a first-time seizure (N = 132,852), we observed 2,090 cancers during < 1 year of follow-up, and 3,785 cancers over 20 years of follow-up. The absolute risk of any cancer was 1.59% (95% CI: 1.52-1.65%) at one year of follow-up after seizure, increasing to 4.75% (95% CI: 4.60-4.91%) at 20 years of follow-up. The SIR was 5.23 (95% CI: 5.01-5.45) for the first year, and 1.27 for years 1-20 (95% CI: 1.23-1.31).
In age-stratified analyses, the SIR was 2.04 (95% CI: 1.42-2.86) for children ≤5 years (N= 74,207) for the first year of follow-up and 5.37 (95% CI: 5.14-5.61) for patients aged ≥6 years (N = 58,645). Finally, the number of patients needed to be screened to detect one excess cancer was 79 (95% CI: 74-83) for all cancers.

Conclusions: A first-time seizure was associated with increased short-term and long-term risks of cancer, particularly in patients aged ≥6 years. Targeted screening evaluations in this high-risk population may improve early detection of malignant diseases.