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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:

Trends in incidence and survival of several types of childhood cancer

To measure progress and to provide information prior to concentration of childhood care in the Netherlands we have studied already several types of childhood cancer: acute lymphoid leukemia (ALL), acute myeloid leukemia (AML), Hogkin lymphoma, Non-Hodgkin-lymphoma, neuroblastoma, renal tumors and extracranial germ cell tumors.

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. Pieter Wesseling.

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.

Recently, we have compared incidence, survival  and mortality of cancer in children and young  adolescents between Belgium and the Netherlands for the period of diagnosis 2004-2015. Results of this collaborative effort with the Belgian Cancer Registry have been published in the International Journal of Cancer (2024). Pubmed PMID: 38478912

We are also participating in the Benchista-study, an international project on benchmarking childhood cancer survival by stage.

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 myeloid leukemia

Adolescents and young adults (AYAs) with acute myeloid leukemia (AML) have a worse survival than pediatric patients. In a recent study, we have showed that this was also the case in the Netherlands between 1990 and 2015. Importantly, the survival gap was largest (almost 20 percent-points) in the most recent time period.

In this project, we examine factors contributing to the survival disparity between AYAs and children diagnosed with AML in the Netherlands by combining detailed information on disease biology and treatment from existing population-based and trial databases. 

This project is performed in close collaboration with prof. Michel Zwaan and prof. Marc Raaijmakers (HOVON / ErasmusMC).

Survival disparities between children and young adults for the major subtypes of non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) is a relatively common type of cancer in children and young adults (AYAs). It has been shown that AYAs with NHL have poorer survival than children. However, the survival disparity may vary depending on subtype.

Using population-based data from the Netherlands Cancer Registry, we compared survival of children and AYAs diagnosed with NHL in the Netherlands between 1990 and 2015 for the major subtypes. AYAs with T-lymphoblastic lymphoma (T-LBL) and Burkitt lymphoma (BL) had a worse prognosis than children with these subtypes. For BL, the survival disparity decreased over time and only persisted for the oldest AYAs in recent years. Children and AYAs with diffuse large B-cell lymphoma (DLBCL) and anaplastic large cell lymphoma (ALCL) had similar survival. Interestingly, children with DLBCL are more dose-intensively treated than AYAs. 

This study is performed in close collaboration with pediatric hemato-oncologists from the Princess Máxima Center for pediatric oncology and hemato-oncologists from adult wards.

Survival disparities between children and young adults with Ewing sarcoma

Ewing sarcoma is a tumor of the bone and soft tissues that typically affects children and young adults (AYAs). AYAs with Ewing sarcoma were reported to have a worse survival than children. However, findings specified by important clinical factors, that may vary with age, are limited. 

In this project, we comprehensively evaluate population-based survival of children and AYAs diagnosed with Ewing sarcoma in the Netherlands over three decades considering tissue of origin, tumor site, and disease stage.

This project is being performed in close collaboration with prof. Hans Merks and other (pediatric and adult) oncologists and orthopedic surgeons. 


TransExpo is an international project that studies whether living near a transformer that converts high voltage from the electricity network into 230 Volt could lead to an increase in childhood leukemia. In the Netherlands, the research was carried out by the Institute for Risk Assessment Sciences at Utrecht University in collaboration with the Prinses Máxima Center for pediatric oncology. 
The evidence for an elevated risk of childhood leukemia in children living near transformers was weak. However, due to the small number of included patients, it was not possible to make any strong conclusions. Results have been published in Environmental Research (2024). Pubmed PMID: 38346482 

Karim-Kos group