A systematic review of the barriers and facilitators influencing the cancer screening behaviour among people with intellectual disabilities

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Introduction

Cancer screening is a preventive healthcare service that helps detect precancerous lesions or epithelial abnormalities signifying any cancer development early, and could serve as an effective means of secondary prevention of cancer [1] . Various health organisations and oncology societies, such as the United States Preventive Services Task Force and the American Cancer Society, have published guidelines on cancer screening, in which the regular utilisation of screening for various cancer types, including breast, cervical, colorectal, lung and prostate cancers, is recommended [23] . Notably, cancer screening utilisation was shown to have the potential to reduce cancer incidence and mortality globally [45] . Thus, universal cancer screening should form part of the global cancer prevention strategy, and cancer screening coverage should be increased to provide every individual with the opportunity to receive cancer screening services.

Despite the wide availability of cancer screening services to the public, disparities in cancer screening uptake have been reported between individuals with and without disabilities. Individuals with disabilities have a significantly lower cancer screening uptake than those without [67] . Among disabled individuals, those with intellectual disabilities (ID) are likely to be of greater concern, as they are especially vulnerable to inequities in healthcare access [8] . ID are generally caused by incomplete mental development, leading to limitations in intelligence, learning, and social functioning [910] . Overall, individuals with ID would exhibit limited intellectual functioning and adaptive behaviours, and they need support with their social, communication and interpersonal skills, and carrying out activities of daily living [11] . Individuals with ID have been reported to face difficulties in the utilisation of healthcare services, including cancer screening, because of their reduced ability to communicate, their financial issues, and insufficient knowledge and training in working with individuals with ID among healthcare professionals [1213] . They are in need of carers to accompany them to attend cancer screening appointments to address issues such as difficulties in communication with cancer screening providers, as evidenced by the finding that a lack of support by carers is a potential barrier to cancer screening utilisation among individuals with ID [14] . Indeed, previous studies have reported that individuals with ID are less likely than the general population to utilise cancer screening 151617 . A recent study also reported that the utilisation rate of breast and cervical cancer screening is significantly lower among individuals with severe ID than among the general population, although no significant difference was observed in the screening utilisation rate between the general population and those with mild ID [18] . In light of these findings, strategies to enhance the cancer screening utilisation rate of by individuals with ID, such as enhancing their access to cancer screening services and intention to undergo screening need to be developed.

Given the need for promoting cancer screening uptake among individuals with ID, a better understanding of the factors that affect their cancer screening behaviours, as well as the barriers to and facilitators of their utilisation of cancer screening, is required. This would inform the strategies that may be implemented to improve cancer screening uptake among these individuals. A review on the factors that may be associated with changes in cancer screening behaviours specifically among individuals with ID was published in 2013, but this review focused only on the barriers to cancer screening among these individuals, and did not review the facilitators of cancer screening [19] . To our knowledge, no recent systematic reviews that include both qualitative and quantitative studies have been conducted to summarise both the barriers and facilitators to cancer screening utilisation among individuals with ID. The objective in our review was therefore to explore the factors associated with, including barriers to and facilitators of, cancer screening utilisation among individuals with ID.