Functional Health Illiteracy in Cancer Patients and Caregivers in the Era of Precision Medicine and Immunotherapy: A Narrative Review

Functional health illiteracy is a significant barrier to equitable cancer care for patients and caregivers, a challenge that is exacerbated by precision medicine and immunotherapy. This review article aimed at synthesizing current evidence on functional health illiteracy among cancer patients and caregivers and examines its interaction with the demands of precision medicine and immunotherapy. The article also outlines practical strategies to mitigate the impact of health illiteracy on therapy adherence, decision-making, and clinical outcomes. Articles published between 2010 and 2025 were identified through searches of PubMed, CINAHL, and PsycINFO. Policy reports from the National Cancer Institute, the Institute of Medicine, and the American Society of Clinical Oncology were also included to provide contextual background. Consistency in article selection was assessed using the K coefficient. Approximately 36-50% of cancer patients were found to be unable to effectively use health information. Older adults, racial and ethnic minorities, and individuals with lower incomes are disproportionately affected. The complex terminology of precision oncology further complicates matters for patients and caregivers, who must manage intricate drug regimens and monitor for immune-related side effects at home. Low health literacy is associated with reduced clinical trial enrollment, decreased therapy adherence, increased emergency department visits, and poorer survival. Interventions, including plain-language use, culturally tailored instructions, digital health skill development, and organizational modifications, have demonstrated efficacy in enhancing health literacy among cancer patients and caregivers. These approaches improve access to medical information, reduce misunderstandings, and support self-management. As precision medicine evolves, aligning clinical complexity with targeted health literacy strategies is essential to optimize adherence, decision-making, and clinical outcomes.