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Journal of Clinical Oncology, Vol 25, No 33 (November 20), 2007: pp. 5262-5266 © 2007 American Society of Clinical Oncology. DOI: 10.1200/JCO.2007.12.3802 Disability in Adult Survivors of Childhood Cancer: A Swedish National Cohort Study
From the Centre for Epidemiology, National Board of Health and Welfare; Department of Women's and Children's Health, Uppsala University Hospital; Karolinska Institutet, Department of Public Health Sciences; National Institute for Psychosocial Medicine; Karolinska Institutet, Department of Woman and Child Health, Childhood Cancer Research Unit, Stockholm, Sweden Address reprint requests to Krister K. Boman, Karolinska Institutet, Childhood Cancer Research Unit, Astrid Lindgren Children's Hospital Q6:05, 171 76 Stockholm, Sweden; e-mail: Krister.Boman{at}ki.se
Purpose We studied the effects of childhood or adolescent cancer and cancer treatment on disability as indicated by persistent aid needs in adult life. Patients and Methods A group of 2,503 survivors of childhood cancer diagnosed before their 16th birthday were studied with data from registers in a national cohort of 1.91 million Swedish residents. Disability indicators were created from information in national registers about income (sickness pension, handicap allowance), personal assistance, and family situation in 2002. Multivariate logistic regression on the log scale was used to estimate relative risk (RR) ratios. Results A total of 7.6% of survivors received handicap allowance indicating permanent disability, including brain tumors (14.0%), other solid tumors (6.3), and leukemias/lymphomas (2.9%), compared with 0.6% in the general population. Twenty-six percent of survivors of CNS tumor and 10% of survivors of solid tumors had at least one indication of a disability. Younger age at diagnosis suggested a higher risk for disability. CNS tumor survivors had an RR of 10.7 (95% CI, 9.3 to 12.8) for having at least one disability indication compared with the noncancer population, whereas leukemia and lymphoma survivors had an RR of 3.0, and survivors of other cancers had an RR of 3.8. Survivors of CNS tumor only had an increased RR for living in the parental household (RR = 1.6; 95% CI, 1.4 to 1.9). Conclusion Childhood cancer survivors more often have persistent needs of supportive measures provided by community and/or the parental household. The survivors of CNS tumors were at particular risk, indicating a need of safer treatment protocols, and tailored follow-up, prevention, and rehabilitation to address this persistent social disability.
During the last decades, the development of multimodal therapy and the introduction of enhanced treatment protocols have resulted in increased survival rates for patients treated for childhood cancer. Predictions suggest that one in 250 individuals in the adult population in high-income countries will be a survivor of a childhood malignancy in 2010.1 The long-term late effects of advanced cancer therapy are not fully known at the time of treatment, and characteristically some adversities do not become evident until years after completion of cancer treatment.1 Likewise illness and/or treatment can result in minor or significant effects on social outcomes, which can be evaluated only after the patient has reached adulthood.2,3 A Danish register study of childhood cancer survivors as young adults found that illness and treatment did not affect late social outcomes such as education; however, tumors in the CNS were an unfortunate exception.4 In contrast, clinical studies based on self reports have indicated considerable persistent impairment in a variety of social outcomes and many aspects of the daily life of survivors.2,5-9 Regarding health and functional late effects, studies have more consistently shown long-term survivors to generally be at risk. In a large (n = 9,535) study from the United States using data from medical records and self-assessment, the risk for functional impairment was five times higher among the survivors compared with their siblings, and 44% reported at least one adversely affected health status domain.10 In a Canadian study (n = 1,334), 8.7% of the survivors reported at least two organs with a dysfunction, and considerable physical as well as psychosocial impairment was linked to this subgroup of survivors.11 High rates of various chronic health conditions have been confirmed in extensive clinical studies of even larger study cohorts (N = 10,397).12 The results from self-report studies thus suggest that register outcome measures such as education and employment may be too crude for capturing important facets of the social adaptation in childhood cancer survivors.
In the Swedish social welfare system the state takes considerable financial responsibility for its 9 million residents to provide protection against financial risks associated with illness, disability, and old age. In 2006, the social insurance expenditure totaled US
This study was based on Swedish National Registers, compiled by the National Board of Health and Welfare and Statistics Sweden, linked through each individual's unique personal identification number. The study population included all individuals born in Sweden in 1962 to 1981 who were registered as residents in Sweden in December 2002, with the exception of the 11,900 individuals who had received a first cancer diagnosis after the 16th birthday according to the Swedish Cancer Register. In this study population of 1,905,013, there were 2,503 survivors who had received a cancer diagnosis before their 16th birthday according to the Swedish Cancer Register. CNS tumors and acute lymphatic leukemias made up approximately half of these cases, with a wide variety of cancers in the remaining half of the group (Table 1).
Socioeconomic Indicators of the Childhood Household The mothers of the individuals in the study were identified in the Swedish Multigeneration Register. The socioeconomic status of the household of the mother was identified in the last Swedish Population and Housing Census of 1980, 1985, or 1990 before the study participants had their 19th birthday. Socioeconomic groups were defined according to a classification created by Statistics Sweden, which is based on occupation but also takes the level of education, type of production, and position at work of the head of the household.14 The highest education completed by the mother was retrieved from the Swedish Educational register of 1990 and classified into low (0 to 11 years), intermediate (12 to 14 years), and long (15+ years). Maternal country of birth was retrieved from the register of the total population in 1986. Maternal country of birth was categorized into four geographic groups: Sweden, Nordic countries, rest of Europe, and the rest of the world.
Outcomes
Statistical Methods
Sociodemographic data and data about childhood cancer status are listed in Table 2. The childhood cancer survivors, and particularly those who had survived leukemia or lymphoma, had a younger mean age than the rest of the population, but in other respects sociodemographic differences were marginal.
Social outcomes in relation to diagnosis are presented in Table 3: 11.0% of all childhood cancer survivors received sickness pension, 7.6% received handicap allowance, and 1.3% received disability assistance; 13.8% of all survivors had at least one indicator of disability with the highest frequency in survivors of CNS tumors (26.2%).
Survivors of CNS tumors had an increased risk for having at least one indication of disability, with a relative risk (RR) of 10.7 (Table 4) compared with the noncancer population after adjustment for sociodemographic confounders, whereas survivors of leukemia or lymphoma had an RR of 3.0 and survivors of other childhood cancers had an RR of 3.8. Increased risk for living in the parental household was found for the CNS tumor survivors only, with an RR of 1.6 compared with the noncancer population (Table 4).
The effects in Table 4 did not differ between male and female cancer survivors, but when the cancer survivors were divided into two groups by age at diagnosis (0 to 6 and 7 to 15 years), a distinct pattern was identified. Survivors of leukemia or lymphoma diagnosed before school age had a higher RR of disability 3.8 (95% CI, 2.6 to 5.5) in an age- and sex-adjusted regression analysis, compared with 2.2 (95% CI, 1.5 to 3.3) in those who were school age when diagnosed (data not presented in tables). A similar pattern for disability was identified for solid tumors, with an RR of 4.8 (95% CI, 3.7 to 6.3) for children at 0 to 6 years versus an RR of 2.8 (95% CI, 2.1 to 3.9) for children diagnosed at age 7 to 15 years. For survivors of brain tumors the risks were similar between the two age groups.
Swedish National Register data on incomes associated with disability and illness turned out to be sensitive indicators of disability among childhood cancer survivors, affecting 13.8% of all survivors (compared with 2.7% in the population of comparison in the same age). They also elucidated the vulnerability of certain subgroups, especially survivors of CNS tumors (RR = 10.7) but also survivors with a diagnosis at younger than age 7 years (blood/lymph cancer, RR = 3.8; solid tumors, RR = 4.8). Living in the household of parents was equally common among survivors and the population of comparison in the same age, with the exception of more CNS tumor survivors, among whom living in parental household was more frequent. Children who were diagnosed with leukemia, lymphoma, or solid tumor before school age had a higher risk of disability in young adulthood compared with those diagnosed at an older age, whereas disability outcomes in survivors of brain tumors were independent of age at diagnosis. Survivors of leukemia are always exposed to chemotherapy and survivors of solid tumors are often exposed to chemotherapy, of which, for example, ifosfamide and intrathecal methotrexate have a known potential of resulting in both endocrine and neurocognitive sequelae.15,16 Our study suggests that the long-term effects of this exposure are more severe in the younger children. This is in accordance with the growing number of empirically based indications about the risks after multimodal treatment at an early age. Focal irradiation constitutes a risk factor, although functional shifts to unimpaired parts of the young developing brain may compensate for anatomic damage. Diffuse insults, such as those induced by chemotherapy, may result in more extensive functional deficits.17 Factors such as increased dependency on adults/parents (for a discussion, see Langeveld et al2) and few peer contacts3 are important determinants of the age at which young persons leave their parental homes to live on their own. The child cancer survivors had left home to the same extent as same-age nonaffected peers—again, the CNS tumor survivors were the exceptions. Overall, our findings appear to be in line with previous studies in this field,2,18,19 although in some studies survivors in general have been found to more often live with their parents when compared with reference persons with no history of cancer.2 One advantage of the register design used in this study is that it makes it possible to study an entire population of childhood cancer survivors without attrition. Interestingly enough, our findings confirm those reported from previous clinical studies, despite the fact that these studies sometimes are characterized by various degrees of attrition. The coverage and the validity of the register data are high, given that the register includes reports from a clinician as well as a pathologist in almost every case; 99% of the cancer cases are morphologically verified.20 The register approach, however, also suggest narrow limitations in the quite crude outcome measures available. Given that all of the individuals in the study groups are anonymous to the research group, it is not possible to supplement our data with more refined data; for instance, with questionnaires aimed at illuminating more subtle information about relations and partners. Social outcomes can be expected to be even more sensitive to the sociocultural context than medical and psychological outcomes. Unemployment, for instance, may be influenced not only by political decisions concerning the social welfare systems and availability of specially adapted work places and tasks, but also by more complex social phenomena such as employer attitudes.7 As an illustration of this, a recent meta-analysis has demonstrated that survivors in the US have a three-fold increased risk of unemployment, whereas European survivors display no increased risk on a group level.7 In the Scandinavian countries and others with a similar social welfare system, there is actually a risk that data about employment obscure the negative aspects of psychosocial outcome for childhood cancer survivors. Our disability data offer a more nuanced way to describe psychosocial outcome when using a register approach. In conclusion, this study demonstrates that childhood cancer survivors are at risk of presenting late disability in young adulthood compared with the general population. This is particularly the case for survivors of brain tumors, but to a certain extent also for survivors of leukemias/lymphomas and solid tumors. These subgroups of survivors need to be targeted in clinical practice so that that treatment protocols, follow-up, prevention, and rehabilitation can be tailored to address the individual needs of these patients.
The author(s) indicated no potential conflicts of interest.
Conception and design: Anders Hjern, Frank Lindblad, Krister K. Boman Financial support: Krister K. Boman Administrative support: Krister K. Boman Provision of study materials or patients: Anders Hjern Collection and assembly of data: Anders Hjern Data analysis and interpretation: Anders Hjern, Frank Lindblad, Krister K. Boman Manuscript writing: Anders Hjern, Frank Lindblad, Krister K. Boman Final approval of manuscript: Anders Hjern, Frank Lindblad, Krister K. Boman
Supported by Children's Cancer Foundation of Sweden, Swedish National Association for Cancer Sufferers and Traffic Accident Victims, and Karolinska Institutet/Stockholm County Council research grants (ALF-funding). Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.
1. Wallace H, Green D: Late Effects Of Childhood Cancer. London, United Kingdom, Hodder Education, 2003 2. Langeveld NE, Ubbink MC, Last BF, et al: Educational achievement, employment and living situation in long-term young adult survivors of childhood cancer in the Netherlands. Psychooncology 12:213-225, 2003[CrossRef][Medline] 3. Barrera M, Shaw AK, Speechley KN, et al: Educational and social late effects of childhood cancer and related clinical, personal, and familial characteristics. Cancer 104:1751-1760, 2005[CrossRef][Medline] 4. Koch SV, Kejs AM, Engholm G, et al: Educational attainment among survivors of childhood cancer: A population-based cohort study in Denmark. Br J Cancer 91:923-928, 2004[Medline] 5. Patenaude AF, Kupst MJ: Psychosocial functioning in pediatric cancer. J Pediatr Psychol 30:9-27, 2005 6. Langeveld NE, Stam H, Grootenhuis MA, et al: Quality of life in young adult survivors of childhood cancer. Support Care Cancer 10:579-600, 2002[CrossRef][Medline] 7. de Boer AG, Verbeek JH, van Dijk FJ: Adult survivors of childhood cancer and unemployment: A metaanalysis. Cancer 107:1-11, 2006[CrossRef][Medline] 8. Stam H, Grootenhuis MA, Last BF: The course of life of survivors of childhood cancer. Psychooncology 14:227-238, 2005[CrossRef][Medline] 9. Evans SE, Radford M: Current lifestyle of young adults treated for cancer in childhood. Arch Dis Child 72:423-426, 1995 10. Hudson MM, Mertens AC, Yasui Y, et al: Health status of adult long-term survivors of childhood cancer: A report from the Childhood Cancer Survivor Study. JAMA 290:1583-1592, 2003 11. Maunsell E, Pogany L, Barrera M, et al: Quality of life among long-term adolescent and adult survivors of childhood cancer. J Clin Oncol 24:2527-2535, 2006 12. Oeffinger KC, Mertens AC, Sklar CA, et al: Chronic health conditions in adult survivors of childhood cancer. N Engl J Med 355:1572-1582, 2006 13. Lindström K, Haglund B, Winblad B, et al: Preterm infants as young adults: A national cohort study. Pediatrics 120:70-77, 2007 14. Statistics Sweden: Socio-Economic Classification (SEI). Stockholm, Sweden, Statistics Sweden, 1982 14. Xhang J, Yu K: What's relative risk. A method of correcting the odds ratios in cohort studies of outcomes. JAMA 280:1690-1691, 1998 15. Raymond-Speden E, Tripp G, Lawrence B, et al: Intellectual, neuropsychological, and academic functioning in long-term survivors of leukemia. J Pediatr Psychol 25:59-68, 2000 16. Anderson NE: Late complications in childhood central nervous system tumour survivors. Curr Opin Neurol 16:677-683, 2003[CrossRef][Medline] 17. Mulhern RK, Merchant TE, Gajjar A, et al: Late neurocognitive sequelae in survivors of brain tumours in childhood. Lancet Oncol 5:399-408, 2004[CrossRef][Medline] 18. Koch SV, Kejs AM, Engholm G, et al: Leaving home after cancer in childhood: A measure of social independence in early adulthood. Pediatr Blood Cancer 47:61-70, 2006[CrossRef][Medline] 19. Boman KK, Bodegård G: Life after cancer in childhood: Social adjustment and educational and vocational status of young adult survivors. J Pediatr Hematol Oncol 26:354-362, 2004[CrossRef][Medline] 20. Centre for Epidemiology: Cancer Incidence in Sweden 2004. Stockholm, Sweden, The National Board of Health and Welfare, Centre for Epidemiology, 2006 Submitted April 30, 2007; accepted August 20, 2007.
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Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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ABSTRACT
INTRODUCTION
$64.830 billion (447.216 billion Swedish Crowns), representing 15.8% of the gross national product. Subsidies due to illness and disability amounted to US 
$19.742 billion, which among other entries included sickness benefit US 
