Sixty Years of Population-Based Survival Monitoring in Childhood and Adolescent Cancer: Evidence from Slovenia

Tina Žagar^*Mojca BirkAna MihorMaja JurtelaUrška TomšičKatarina LokarTeja OblakNika BricSonja TomšičMiran MlakarVesna Zadnik

• Institute of Oncology Ljubljana, Ljubljana, Slovenia

Background. Long-term survival of children and adolescents (CA) diagnosed with cancer has hardly been researched in Slovenia. Our aim was to present the survival trend at the population level over a period of 60 years with an additional comparison between observed and net survival. Methods. From the Slovenian Cancer Registry, we obtained data on malignant cancer cases (excluding cases of non-melanoma skin cancer) in CA aged 0‒19 years diagnosed in Slovenia in 1964–2023. Survival estimates were calculated using the Kaplan-Meier estimator for observed survival and the non-parametric Pohar-Perme estimator for net survival by age, period and ICCC groups. Results. Of the total 4,067 cancer cases, 3,935 first primary cancers were included in the survival analysis. A steady increase in the crude incidence rate was observed over the 60-year period, from 10.9 per 100,000 in the period 1964–1973 to 17.7 per 100,000 in the period 2014–2023, largely on account of increases in ICCC groups I, II, IV, X and XI. For ICCC cancer groups I, II, IV, V, VI and X, the change in the 10-year net survival was more than 50 percentage points, while at the same time for groups V and VI the 10-year net survival for patients diagnosed in the period 2004–2013 was 100%. The observed five-year survival 30.8% (27.3−34.8%) in the period 1964–1973 steadily increased to 87.8% (85.3−90.3%) in the period 2014–2023. The five-year observed survival in the period 2014– 2023 was worst for children diagnosed at the age of 1–4 years (83.6%, 77.8–89.9%) and best for adolescents diagnosed at the age of 15–19 years (90.2%, 86.3–94.2%). The differences between the observed and net survival were very small, with a difference exceeding 1 percentage point for survival of 30 years or more. Conclusions. Increasing survival among Slovenian children and adolescents indicates significant progress in cancer diagnosis and treatment. The need for systematic surveillance of the late effects of cancer treatment is increasing with the growing number of survivors (resulted from decreasing mortality and increasing survival) in order to maintain their health and quality of life as they age.