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Karim-Kos group

We focus on analysing childhood cancer statistics. Looking at these statistics, we aim to expand our knowledge about the incidence of childhood cancer, its spread in the population, possible causes and prognosis. Together, these are known as cancer surveillance. Secondly, we focus on unraveling the causes behind differences in outcomes between children and young adults diagnosed with the same cancer type to improve quality of care and outcomes in both patient groups, and to stimulate collaborations between pediatric and young adult cancer care units.

Group leader: Dr. Henrike Karim-Kos
Phone +31 618418717


"Epidemiological data provide insight into the progress that we are making in our fight against childhood cancer" Dr. Henrike Karim-Kos - Group leader
Childhood cancer surveillance

Cancer surveillance provides interesting information for and can be used in the development and evaluation of new interventions in two domains: a) the public health domain (population-level) focusing on primary and secondary prevention, and b) the clinical domain (patient-level) focusing on quality of care, prognosis and quality of life. Progress made in one or both domains can be assessed by standard surveillance measures: incidence, stage at diagnosis, survival and mortality. These measures are comparable on an international level and are available for the Netherlands since the 1990s.

In pediatric oncology, the largest intervention in the Netherlands has been concentration of care in one single center as of 2018, namely the Princess Máxima Center for pediatric oncology, with the ambition to improve the outcome of childhood cancer. It is important to investigate the effect of this centralisation on quality of care and ‘cure’ in the future. Therefore, information on the prior situation is fundamental. Evaluation of pediatric cancer care, focusing on both the past and the future, is one of the main goals of our research group.


Our current research programs focus on:

  • Epidemiology of high grade brain tumors in children and treatment outcomes.

    Brain tumors are the most common solid tumors in children and around 50% of these tumors are classified as high-grade. Pediatric high-grade brain tumors are among the most devastating childhood cancers, associated with dismal survival outcomes and high morbidity rates. Underlying reasons for these poor survival outcomes are the aggressive nature of these tumors and the limited treatment options.

    Until now, scientific knowledge regarding prognostic factors in high-grade brain tumors in children is limited to tumor biology and basic clinical information. Therefore, it is difficult to predict survival of children with a high-grade brain tumor.

    By using population-based epidemiological data and combining this with additional clinical and biological information, we hope to gain insight into the relationship between tumor characteristics, diagnostics, treatment strategies and survival outcomes. To date, no integrative approach has been used that takes all these factors into account. The results of this project will ultimately lead to a better understanding and prediction of survival in children with a high-grade brain tumor.

    This project is performed in close collaboration with the research groups of prof. Eelco Hoving, dr. Dannis van Vuurden and prof. Leontien Kremer.


  • Time trends in incidence and survival outcomes of renal tumors in children

    Malignant renal tumors are one of the most common solid tumors diagnosed in children below the age of 5 years. The large majority (90%) of renal tumors in children are Wilms tumors (WT) with an age-standardised incidence rate of about 8 per million person-years in high-income countries. Although most patients with WT have a favorable prognosis, survival of WT seems to have stabilized in Europe since the early 2000s.

    In the past, two main approaches existed for the treatment of pediatric renal tumors in the Netherlands, namely the Children’s Oncology Group (COG) and the International Society of Pediatric Oncology (SIOP) protocols, which differ regarding the timing of nephrectomy.

    In this project, we describe trends in incidence, survival, and mortality of pediatric renal tumors in the Netherlands between 1990-2014 to provide an historical view on the progress made. This will also serve as a baseline measurement for future evaluations of renal tumor care.

    This project is performed in close collaboration with the research group of prof. Van den Heuvel-Eibrink.


  • Time trends in incidence and survival outcomes of soft tissue and bone sarcomas.

    Soft tissue and bone sarcomas are the second most common type of solid tumors in children comprising about 10% of all pediatric malignancies. Until now, no comprehensive national trend analyses on trends in these tumors have been performed.

    In this project, we describe trends in incidence, stage at diagnosis, treatment, and survival outcomes of sarcomas in the Netherlands since the 1990s to provide an historical view on the progress made. Findings of this project will serve as a backbone for future research and evaluations.

    This project is performed in close collaboration with the research group of dr. Merks.


  • International comparisons of surveillance measures.
    Our research group is active in international comparative studies on surveillance measures. Our collaborative network consists of various European Cancer Registries and the International Agency for Research on Cancer (IACR), Lyon.


Outcome disparities between children and young adults with cancer

For several cancer types, adolescents and young adults (AYAs, 18-39 years) have a worse prognosis compared to pediatric patients (0-17 years). The exact reasons for the inferior outcomes of AYAs with cancer are, however, still not clear. Notably, in the context of the Netherlands, possible causes have hardly been studied at all. The focus of our research group is to determine factors contributing to the outcome disparities between AYAs and children diagnosed with cancer.

Our current research program focuses on:


  • Reducing survival disparities between pediatric, adolescent, and young adult patients with acute lymphoblastic leukemia and acute myeloid leukemia (SURVGAP ALL/AML)

    Adolescents and young adults (AYAs) with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) have a worse survival than pediatric patients. Use of pediatric instead of adult regimens in AYA ALL has been shown to improve outcome and pediatric inspired-protocols have been introduced for patients aged ≤40 years in the Netherlands since 2005. However, a “survival gap” remains. Regarding AML, the survival gap is even increasing in recent years.

    In this project, we examine factors contributing to the survival disparity between AYAs and children diagnosed with ALL and AML in the Netherlands by combining existing population-based and trial databases with additional molecular analyses/cytogenetic testing. 

    This project is performed in close collaboration with prof. Vormoor (Princess Máxima Center for pediatric oncology), prof. Raaijmakers and dr. Rijneveld (both from HOVON / ErasmusMC), and hemato-oncologists from UMC Utrecht.


TransExpo is an international project that studies whether living near a transformer vault that converts high voltage from the electricity network into 220 Volt could lead to an increase in childhood leukemia. In the Netherlands, the research will be carried out by the Institute for Risk Assessment Sciences at Utrecht University in collaboration with the Prinses Máxima Center.

Karim-Kos group