Representation

1. 1. How are adults with intellectual and/or developmental disabilities identified in administrative data sources (e.g., medical only, social services, education) used in population-based cancer research. Which diagnoses are included in these algorithms? What detail are available on their underlying health condition interacting with systems, people and environment to cause disability? What information is considered on the supports they receive, in which settings.

Involvement

1. 2. How are adults with intellectual and/or developmental disabilities recruited in non-administrative data studies? Are they themselves specifically recruited and consented, or are those involved in their care/caregivers recruited? Are caregivers (paid and unpaid, including family members and support workers) recruited as proxy respondents for adults with intellectual and/or developmental disabilities and/or for reporting their experiences of caring for an individual with intellectual and/or developmental disabilities and cancer? How might recruitment strategies be biased or rely on gatekeeping?
2. 3. How are healthcare professionals recruited to report on their experiences of providing cancer care to adults with intellectual and/or developmental disabilities and cancer?

Engagement

1. 4. How are adults with intellectual and/or developmental disabilities and/or their carers (family members, paid/unpaid caregivers, and healthcare professionals) engaged in the research (e.g., as research participants, as proxies, or as co-researchers/advisors)?
2. 5. How are adults with intellectual and/or developmental disabilities and/or their carers (family members, paid/unpaid caregivers, and healthcare professionals) engaged in cancer research based on the International Public Participation spectrum [35] (are co-researchers/advisors informed, consulted, involved, collaborated with, or empowered)?

Patient and public involvement

For the development of this protocol, we consulted with two paid advisors: 1) an adult with intellectual and/or developmental disabilities who has undergone participated in cancer screening, 2) a parent of an adult child with intellectual and/or developmental disabilities with ovarian cancer. The advisors provided initial feedback on the aims of the scoping review. We will meet regularly with both advisors throughout the duration of the scoping review, including while completing the narrative summary and when developing strategies for accessible and inclusive knowledge sharing recommendations from the findings. Co-authorship or formal acknowledgement in the full review publication will be offered to reflect their contributions to the interpretation of the data.

Participants

This review will include studies involving adults aged 18 years and older with intellectual and/or developmental disabilities receiving preventive and cancer-related care (e.g., see relevant International Classification of Disease 9 and 10 codes in S1 Table). Intellectual and/or developmental disabilities refer to conditions that originate during the developmental period, affecting intellectual functioning, social skills, and adaptive functioning [38]. Disability arises based on the interaction between persons with conditions, and societal barriers, including physical and environmental barriers as well as systemic systems of oppression, such as negative attitudes and bias [39]. We will also include studies involving family members, caregivers, support workers, or healthcare professionals providing support to adults with intellectual and/or developmental disabilities receiving cancer-related care. Eligibility will focus on research conducted at various points along the cancer control continuum, including cancer awareness/literacy, screening, incidence, stage at diagnosis, treatment, survival, survivorship, psycho-social oncology, supportive care, and end-of-life care. For studies with samples of adults with a mixed range of disabilities (i.e., physical and intellectual), we will only include studies that report disagregated data for those with intellectual and/or developmental disabilities.

Concept

This review will consider studies that explore cancer outcomes and experiences of adults with intellectual and/or developmental disabilities. The concept will also include the experiences of family members, caregivers, support workers, or healthcare professionals providing support to adults with intellectual and/or developmental disabilities through their cancer experience.

Context

The context for this review is the direct or indirect experience of care and outcomes related to cancer including awareness/literacy, screening, incidence, stage at diagnosis, treatment, survival, survivorship, psycho-social oncology, supportive care, and end-of-life care among adults living with intellectual and/or developmental disabilities.

Type of evidence sources

The review will consider quantitative, qualitative, and mixed methods study designs. Quantitative studies will include clinical trials, quasi-experimental studies, and observational research. Qualitative studies will consist of various study traditions, including participatory action research, ethnographies, case studies, phenomenology, and grounded theory. Mixed methods studies will be included when components of the qualitative or quantitative findings can be extracted separately.

Exclusion criteria

We will exclude studies that do not provide specific outcomes or experiences for adults with intellectual or developmental disabilities (e.g., disability generally), focus on pediatric cancers (age < 18 years), as well as reviews, editorials, case reports, and non-peer reviewed resources (e.g., dissertations, conference abstracts).

Search strategy

An initial search was conducted by an academic health sciences librarian (SH) in Medline, Embase, PsycINFO and CINAHL using relevant subject headings and text words that corresponded to the main topics in the research question. Two limits were applied to the search strategy that matched to the inclusion/exclusion criteria for the research project, namely adult population and articles published from 2006 to 2025. The librarian checked that five key studies were identified with the search terms. The search is provided in Supplementary materials (S2–S5 Tables). This search was peer-reviewed by a second librarian based on the Peer Review of Electronic Search Strategies (PRESS) guidelines [40]. Two reviewers will also examine the reference lists of included articles for any missed relevant citations. These articles will be screened and reviewed in full as needed. Only articles from 2006 and onwards will be included based on the adoption of the UNCRPD [14]. There will be no language restrictions. The search will be updated within one month of submission to publication of the full results. Currently, our team has completed the screening of titles and abstracts, with full text review underway. We anticipate that the full text screening, extraction, and results to be completed by January, March, and June 2026, respectively.

Source of evidence selection

All articles will be uploaded into Covidence, and duplicates will be removed. Two independent reviewers will review titles and abstracts based on the inclusion criteria (Table 1). Pilot testing of the inclusion and exclusion criteria will be conducted as proposed by JBI [36], with a random selection of 25 articles. Two reviewers will screen based on the eligibility criteria and will subsequently meet to discuss any discrepancies and update the criteria accordingly. The team will only start screening when 80% agreement or greater is achieved. The full text of relevant studies will be retrieved and imported into Covidence. The full text of each study will be reviewed by two independent reviewers based on the same inclusion criteria. Reasons for exclusion of full text articles will be recorded and reported in the review. A third reviewer will be contacted when any conflict arises in the selection process to achieve consensus. The results of the literature search and study inclusion will be summarized in the final scoping review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) [37].

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Table 1. Study inclusion and exclusion criteria.

https://doi.org/10.1371/journal.pone.0346010.t001

Data extraction

For each study, data will be extracted on the study setting, participants, study methods, study design and traditions. We will also extract information on cancer outcomes and experiences studied (e.g., awareness/literacy, screening, incidence, stage at diagnosis, treatment, survival, survivorship, psycho-social oncology, supportive care, and end-of-life care) across cancer locations (e.g., breast, colorectal, lung, etc.). We will extract information on whether adults with intellectual and/or developmental disabilities were included in the study, or if a caregiver, family member, or healthcare professional were recruited as a proxy respondent or as primary participants (e.g., study focus was on experiences of family members, caregivers, etc.). We will also extract information on recruitment of adults with intellectual and/or developmental disabilities and the potential for gatekeeping (e.g., participants recruited through service providers, exclusion of individuals without a family advocate, etc.). Information about the person with intellectual and/or developmental disabilities will be extracted, including demographics (e.g., age, sex, race, gender, rurality), underlying health experiences (e.g., other types of conditions such as diabetes or heart disease), and experiences of disability (e.g., level of adaptive supports needed). We will also consider how intellectual and/or developmental disabilities were operationalized (e.g., yes/no, levels of experience/support required in day-to-day life: little support; some support; extensive support, etc.). If a participant without intellectual and/or developmental disabilities is included, we will extract demographic information about that participant and their relationship to the adult with intellectual and/or developmental disabilities, and whether they served as a proxy respondent for the adult with intellectual and/or developmental disabilities or if their experiences as a carer were specifically explored. Specific information will be extracted on how participants were recruited in the study (e.g., qualitative, some types of quantitative studies, etc.) or identified in health databases (e.g., administrative data studies), as well as how people with intellectual and/or developmental disabilities were involved in the study.

We will extract information and organize reporting of engagement of people with intellectual and/or developmental disabilities in each research study based on a community engagement framework developed by International Association for Public Participation (IPA2; Informed, consulted, involved, collaborated, empowered) [35]. First, we will extract details on whether adults with intellectual and/or developmental disabilities and their carers were engaged in the research as advisors or researchers. We will then identify how these advisors were involved in the research. The goals of each public participation category are: 1) inform: to provide balanced information to assist with understanding the problem and solutions; 2) consult: to get feedback from the persons with lived experience on problem and solutions; 3) involve: to work directly with persons with lived experience throughout the project to ensure their perspectives are considered; 4) collaborate: to partner with persons with lived experience in each aspect of project decision-making; 5) empower: to place decision-making in the hands of persons with lived experience [35]. We will also extract information pertaining to data ownership. If the study focuses on caregivers (paid or unpaid), family members or healthcare professionals, rather than people with intellectual and/or developmental disabilities or involved engagement of these populations as advisors or on the research team, we will also identify how they were involved in the study based on the IPA2 framework. A summary of items for data extraction is available in Table 2. This list will be updated as our team pilots this extraction form for five to ten studies before full extraction. A code book will also be created for resolving ambiguous study details. Data will be extracted by two independent reviewers. Disagreements will be resolved by consultation with a third reviewer.

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Table 2. Data extraction items.

https://doi.org/10.1371/journal.pone.0346010.t002

Data analysis and presentation

Descriptive statistics will be used to summarize study characteristics (type of study, cancer site, type of study design/tradition). We will display how adults with intellectual and/or developmental disabilities were identified in administrative data sources, including diagnoses used to identify intellectual and/or developmental disabilities, across population-based studies. We will present different definitions of intellectual and/or developmental disabilities across studies and outline gaps in the research conducted. Our team will also summarize information provided about adults with intellectual and/or developmental disabilities and their carers, including the extent to which intersectionality is captured or considered (e.g., the intersection of disability and race/ethnicity). Intersectionality will be considered within the context of the social determinants of health noted by the World Health Organization [41]. We will synthesize if and how adults with intellectual and/or developmental disabilities were recruited into studies that involved primary data collection, and whether those involved in their care were recruited as well. Descriptions of consent will be analyzed to determine the extent to which strategies proposed by McDonald et al. (2024) are followed for responsible inclusion [42]. We will display how adults with intellectual and/or developmental disabilities and their family members, caregivers (paid or unpaid), or healthcare professionals were engaged in each study as advisors or co-researchers based on the IPA2 framework [35], namely if participants were informed, consulted, involved, collaborated with, or empowered. Results will be summarized by mapping findings on cancer care milestones. For example, we will consider the representation, involvement and engagement of adults with intellectual and/or developmental disability and their carers in research focused on cancer awareness, prevention, screening, staging, treatment, survival, and end-of-life care. We will also explore changes over time to consider how representation, involvement and engagement of this patient population in cancer-related research have changed over time. Our team will work with our advisors to develop easy read summaries that are accessible when presenting findings to adults with intellectual and/or developmental disabilities and those involved in their care.

Data

Relevant data from this study will be made available upon request following completion and publication.