In this large register-based cohort study nested in the entire populations of three Nordic countries, we observed that, overall, a smaller proportion of childhood cancer survivors had attained upper secondary education by age 25 than population comparisons and siblings. The differences were, however, largely confined to survivors of CNS tumours, while smaller differences were seen for survivors of ALL diagnosed in 1971–1989 or at ages 12–14 years. Survivors of all cancer types experienced delays in education, but survivors of leukaemias other than ALL, lymphomas, and non-CNS solid tumours had caught up with their peers with regard to upper secondary education by age 25. Survivors who had spent more time in hospital during and after their cancer diagnosis or had hospital contacts in early adulthood were at particular risk of not attaining upper secondary education by age 25, especially survivors who had psychiatric hospital contacts. Parental education had a considerable impact on educational attainment in general, however, stratification by parental education showed the largest differences between survivors and population comparisons among those with parents with high education.

The pronounced educational disadvantage of survivors of CNS tumours is well recognised in the literature [4,5,6,7], seen even at younger ages [12, 13]. Our study suggests that this group of survivors does not catch up over time as do survivors of other types of cancer, in accordance with previous findings in Switzerland [9]. We found that survivors of CNS tumours diagnosed before school age were particularly vulnerable, with a somewhat stronger association among females and individuals diagnosed in the early calendar period, similar to previous studies [12, 13, 25]. However, survivors of CNS tumours were less likely to attain upper secondary education by age 25 than their peers in all the strata investigated, highlighting the need to support this group.

Survivors of ALL diagnosed in 1971–1989 also had a lower level of education than their peers at the age of 25. This is probably due to the use of cranial radiotherapy during that period [26]; previous studies also found lower educational attainment among survivors of leukaemia who were treated with irradiation [10, 27,28,29]. The difference between calendar periods was seen mainly among younger children, who are more sensitive to irradiation [30]. We also found that survivors of ALL diagnosed at ages 12–14 were at risk of poorer educational outcomes in both calendar periods. This finding is somewhat unexpected, although some other studies suggested that also older children with leukaemia are at risk of lower educational attainment [9, 10].

We found that survivors who had spent more time in hospital during and after diagnosis and survivors with more hospital contacts in early adulthood, i.e., after the original cancer treatment, were at higher risk of not attaining upper secondary education by age 25. This is in line with previous research of more specific health problems. For example, in the British Childhood Cancer Survivor Study, epilepsy influenced education negatively [27]. A German study of survivors of adolescent cancer suggested that visual or hearing late effects as well as neuropsychological late effects were risk factors for poorer educational attainment at different levels, while increasing length of treatment was borderline significant [31]. This result may also reflect that survivors experiencing a relapse or a second primary malignancy, who therefore have more contacts with hospitals, is a vulnerable group with regard to educational achievements. However, such specific conclusions require further investigation. In our study, the risk of poorer educational outcomes was particularly pronounced among survivors with psychiatric hospital contacts; this finding is important with regard to potential targeted interventions, although this is a small group of survivors as seen in the current study as well as in previous research from our group [11].

It has been shown previously that survivors with parents who had low education had worse educational outcomes than survivors with parents with high education [9, 12, 13], which reflects the pattern in the general population and is also seen in our study population. In addition to existing literature, we observed that the difference between survivors and comparisons was largest among children of parents with high education. This finding runs contrary to sociological theories of “compensatory advantage”, which argue that highly educated parents have more resources to counteract negative childhood circumstances [14], and suggests that childhood cancer is more disruptive for the educational trajectories of children of highly educated parents. Also, as it is less common that children with higher educated parents do not complete upper secondary education, the relative and absolute differences in this group become more pronounced. Indeed, survivors of ALL and non-CNS solid tumours whose parents had low education completed upper secondary education to the same extent or even more frequently than the corresponding population comparisons, which suggests that these groups of survivors gained from provided support. For survivors of CNS tumours, however, the combination of experiencing a cancer diagnosis as a child and having parents with lower education was associated with a particularly high risk of not completing upper secondary education before age 25.

Survivors of non-CNS solid tumours who had attained an upper secondary education attained tertiary education to a similar extent as their peers. A previous meta-analysis showed that survivors without CNS involvement had no disadvantage in achieving tertiary education but highlighted the risk of bias from non-participation [7]. This bias was not a concern in the present study, which strengthens the conclusion that, for this group, childhood cancer can disrupt education primarily in the early stages but has no further impact on later educational transitions. However, for other groups of survivors there seem to be a difference in achievement of tertiary education.

Our study is unique in that it combined high-quality register data from three Nordic countries and included comparisons with both the general population and siblings. Use of siblings as a second reference group controlled for confounding from shared familial and social backgrounds and strengthens the validity of our findings, although these analyses had less statistical power, as only data of siblings discordant for the outcome contributed to the estimates. The large population allowed subgroup analyses, which is important for identifying survivors who would benefit most from targeted support. However, although the whole population of survivors in Denmark, Finland, and Sweden were included, statistical power limited analyses of, for example, more defined cancer types (e.g., specific types of non-CNS solid tumours). As information on educational attainment was obtained from national population-based registers, there was no risk of bias due to self-reporting, non-participation, or selection. Further, the longitudinal information was obtained in the same way for the survivor and comparison groups.

The register-based design and the three-country wide inclusion have many advantages but also some limitations. We had no information on the reasons for delayed graduation, which are not necessarily related to educational problems. We also lacked information on treatment, especially cranial radiation therapy, an established risk factor for poorer educational achievement [4]. Inclusion in future studies of more clinical information would improve understanding of the underlying mechanisms and help to identify vulnerable survivors. Our study population came from three Nordic countries which have remarkably comparable, although not identical, health-, social- and educational systems. The matched design took differences between countries into consideration. Country specific analyses showed similar results, although effect estimates differed somewhat in magnitude. This could reflect true differences across countries but may also be a result of random variation. It is important to acknowledge differences between countries when interpreting the findings, but also the overall Nordic context. Support in school as well as the overall social- and educational systems will impact survivors’ opportunities after a cancer diagnosis, and it is therefore challenging to directly generalise our findings to other countries. We included survivors diagnosed over a long period of time during which treatment regimens have changed, and our results may not be applicable to children undergoing cancer treatment at present. Our findings highlight the importance of continued follow-up of late effects and socioeconomic consequences also among more recently treated survivors.

In this three-country wide register-based cohort study, we demonstrate that, although survivors of childhood cancer are more likely than their peers to experience delays in upper secondary education, many had caught up by the age of 25. Except for survivors of CNS tumours, survivors attained upper secondary education to almost the same extent as their peers. Parental education played an important role also in survivors’ educational attainment and modified the associations. In addition to the vulnerable group of survivors of CNS tumours, we identified survivors who had spent more time in hospital during and after diagnosis and survivors with hospital contacts, particularly for psychiatric diseases, in early adulthood as risk groups for educational difficulties. These findings add to the existing literature and recently published guidelines for surveillance [8] and enhance a possibility of identifying survivors who need additional educational support, both close to the diagnosis and at later follow-up visits.