Definition of Disability

The concept of disability has evolved over the past several decades from a medical to a biopsychosocial model. In the medical model, disability is viewed as a feature of a person that is caused by injury, disease, or other health conditions and managed through medical treatment or modification of an individual’s behavior (WHO, 2001, 2002; see also IOM, 1991; Kaplan, 2000). In contrast, the biopsychosocial model, exemplified by the World Health Organization’s International Classification of Functioning, Disability and Health (ICF), portrays disability as “the interaction between an individual (with a health condition) and that individual’s contextual factors (environmental and personal factors)” (WHO, 2001). The ICF model recognizes functioning in three domains (middle tier of Figure 1-1): (1) body functions and structures, which encompasses physiological functions of the body, including psychological functions, as well as the functioning of body structures (e.g., movement of limbs, cardiac function); (2) activities, which are actions or tasks (e.g., running, problem solving); and (3) participation, which is the performance of tasks in a societal context (e.g., participation in school or organized sports). The ICF model refers to deficits in body function and structure as impairments, deficits in completing activities as limitations, and reductions in participation as restrictions. It should be noted that such accommodations as assistive technologies and environmental modifications are environmental contextual factors that act on the ICF domains to enhance an individual’s activity and participation.

FIGURE 1-1

International Classification of Functioning, Disability and Health model of functioning and disability. SOURCE: WHO, 2001, p. 18.

SSA incorporates function into its definition of disability for children, considering children under 18 to be disabled if they have a “medically determinable physical or mental impairment that causes marked and severe functional limitations, and which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months.”⁴ SSA considers a wide variety of factors when evaluating the effects of an impairment or combination of impairments on a child’s functioning.⁵ These factors include but are not limited to

• how well the child can initiate and sustain activities, how much extra help he or she needs, and the effects of structured or supportive settings (see § 416.924a(b)(5));
• how the child functions in school (see § 416.924a(b)(7)); and
• the effects of the child’s medications or other treatment (see § 416.924a(b)(9)).⁶

SSA looks at “how appropriately, effectively, and independently the child performs their activities (everything they do at home, at school, and in the community) compared to the performance of other children their age who do not have impairments.” In particular, SSA considers functioning in six domains:

• acquiring and using information,
• attending and completing tasks,
• interacting and relating with others,
• moving about and manipulating objects,
• caring for oneself, and
• health and physical well-being.⁷

For a child’s impairment(s) to “functionally equal” the listings, the impairment(s) “must result in ‘marked’ limitations in two domains of functioning or an ‘extreme’ limitation in one domain.”⁸

Timeframes of Interest

The committee recognized that high-quality cancer care spans the continuum of cancer care from diagnosis through end-of-life care. This report focuses on the acute and chronic phases of this continuum. The acute phase occurs immediately after a person has been diagnosed with cancer and generally includes such up-front treatments as surgery and initial chemotherapy and radiation therapies, as well as palliative and psychosocial care as needed by the patient. The chronic phase, which may continue for months to years following initial diagnosis, encompasses ongoing management of the patient with the goal of providing long-term surveillance for cancer recurrence and, in some patients, prolonged adjuvant or maintenance therapies. In addition, patients may receive palliative and psychosocial care to manage residual effects of the cancer and its treatment (IOM, 2013a).

The committee was asked to describe “the minimum period appropriate to consider a childhood cancer disabling under SSA’s definition of disability for children.” In considering this question, the committee noted important differences between disability in children and in adults. Any interruptions to a child’s normal developmental process and experiences can have profound, and potentially lasting, functional effects. Although severe impairments acquired in adulthood also may seriously affect the individual’s function and participation in work and other daily activities, they do not interfere with the normal acquisition of cognitive and social skills that occurs during childhood and adolescence. Thus, a child’s absences from school (and other typical activities) have greater long-term impacts relative to adults’ absences from work; for children, limited functioning relative to peers has a compounding effect.

The committee identified three timeframes of interest with respect to childhood cancers. The first, which addresses the question of “the minimum period appropriate to consider a childhood cancer disabling,” is the period from the child’s cancer diagnosis through active treatment and an anticipated period of recovery from the acute effects of treatment. During the recovery period, the child remains unlikely to be able to participate in school or other activities. The second timeframe is the period following treatment and recovery from any acute effects of treatment, during which the child may continue to experience chronic (ongoing, persistent) effects of treatment and/or develop secondary late effects while still under the age of 18, the age at which SSA’s disability determination process shifts to that used for adults. The third timeframe is the period of adulthood (more than 18 years of age), during which individuals may continue to experience chronic effects or develop late effects of the treatment for their childhood cancer. The committee identified the period of transition from adolescence to young adulthood as particularly important for this study because of the unique issues it presents with respect to cancer treatment, functional impacts, and disability adjudication.

The committee was also asked to describe “clinical standards for identifying ‘cure’ or complete remission.” Cure is a complicated concept, and although it can be achieved in some patients, use of the term is inconsistent among researchers and clinicians. The term “long-term survivor” is preferred as it better communicates the concept that disease-free status comes with significant risk of long-term effects (Haupt et al., 2007; Jankovic et al., 2018).

Selection of Cancer Types

The committee was asked to “provide an overview of the current status of the diagnosis, treatment, and prognosis of select childhood cancers, including different types of malignant solid tumors.” The committee understood the phrase “malignant solid tumors” to refer specifically to a category within SSA’s child cancer listings with the same label, which appears to include all types of malignant solid tumors that are not otherwise specified in the listings. The committee’s selection of cancers for discussion in this report includes not only cancer types that would be captured within SSA’s “malignant solid tumor” category but also other types of solid tumors, including those of the central nervous system (CNS), and hematologic cancers that are specified in the cancer listings.

One of the challenges the committee faced was use of the traditional classification of tumors as “benign” and “malignant.” The distinction between these categories of tumors is often problematic in children, particularly as regards CNS tumors. Not only are these terms misleading with respect to societal understanding and misconceptions, but many “benign” tumors often cause long-standing and permanent late effects, morbidities, and disability, and many can lead to a child’s death. For these reasons, the committee prefers that these terms be avoided. In CNS tumors, the terms “low grade” and “high grade” are often used instead. Many low-grade lesions, such as a low-grade glioma, are treated in the same manner as a high-grade tumor—with surgery, chemotherapy, and/or radiation. The committee therefore chose to include in this report some lesions that historically have been labeled “benign.” Specifically, the committee included certain lesions that often behave and are treated in the same ways as high-grade lesions and typically are not considered “benign” by the pediatric oncology community at large.

Selection of Emerging Treatments

The committee was asked to “provide a summary of select treatments currently being studied in clinical trials.” A number of new treatments and emerging therapies are discussed in this report. Rapidly increasing knowledge of the molecular and genomic bases of cancers has resulted in the development of targeted therapies, also referred to as precision therapies, in which new drugs specifically block the effects of tumor-specific changes, such as tumor mutations. Some of these approaches have been highly successful and have been incorporated into standard therapy for children with newly diagnosed or relapsed cancers. In addition, the development of immunotherapy approaches for pediatric cancers is expanding rapidly. A range of immunotherapy approaches are in development for a variety of tumors. Although less advanced than new agents targeting genomic changes, some immunotherapies have already resulted in effective therapies for children with solid tumors or hematologic malignancies.

Information Gathering

The committee identified a number of established, comprehensive sources of information about childhood cancers that are actively maintained through ongoing literature review. These sources include the National Cancer Institute’s (NCI’s) Physician Data Query^® (PDQ); Children’s Oncology Group (COG) guidelines; and the Surveillance, Epidemiology, and End Results (SEER) Program.

The PDQ provides “comprehensive, evidence-based summaries on topics that cover adult and pediatric cancer treatment; supportive and palliative care; screening; prevention; genetics; and integrative, alternative, and complementary therapies” (NCI, 2020). The pediatric PDQ summaries are reviewed multiple times per year and updated as needed based on ongoing review of newly published literature, and include information about the strength of the evidence supporting each summary.

Treatment for many pediatric patients in the United States is based on the COG’s multidisciplinary treatment protocols. The COG is an international clinical trials group dedicated to childhood and adolescent cancer research. Its clinical trials include front-line treatment for various childhood cancers; studies to determine their underlying biology; and trials involving new and emerging treatments, supportive care, and survivorship. The COG is supported by NCI and involves thousands of childhood cancer experts at more than 200 leading children’s hospitals, universities, and cancer centers. See Appendix C for additional information about the PDQ and the COG.

NCI’s SEER Program represents the primary source for population-based data on cancer incidence and survival in the United States. SEER, supported by the Surveillance Research Program at NCI, collects and publishes data from cancer registries throughout the United States.

The committee used these sources where possible, supplemented by its own additional literature reviews as needed. Further information about these resources, and others, is located in Appendix C.

The committee used a variety of resources to supplement these sources. Meeting in person five times, the committee held three public workshops to hear from invited experts in areas pertinent to its charge (see Appendix A). Speakers at these workshops included experts in psychosocial functioning, neurocognitive functioning, physical functioning, and pain in children during and following cancer treatment. The committee also participated in a panel discussion on functioning in patients and survivors of pediatric cancer, hearing parent, educator, and social worker perspectives.

The committee’s work was further informed by previous reports of the National Academies. These reports included Childhood Cancer Survivorship: Improving Care and Quality of Life (IOM and NRC, 2003), Delivering High-Quality Cancer Care: Charting a New Course for a System in Crisis (IOM, 2013a), Identifying and Addressing the Needs of Adolescents and Young Adults with Cancer: Workshop Summary (IOM, 2013b), Psychological Testing in the Service of Disability Determination (IOM, 2015), Comprehensive Cancer Care for Children and Their Families: Summary of a Joint Workshop by the Institute of Medicine and the American Cancer Society (NASEM, 2015), The Promise of Assistive Technology to Enhance Activity and Work Participation (NASEM, 2017), Opportunities for Improving Programs and Services for Children with Disabilities (NASEM, 2018), Functional Assessment for Adults with Disabilities (NASEM, 2019), and Selected Health Conditions and Likelihood of Improvement with Treatment (NASEM, 2020).