Background: Prognostic understanding in advanced cancer patients and their caregivers may have an impact on the delivery of effective care. The aims of this study were to explore prognostic understanding at diagnosis in both patients with advanced lung cancer and their caregivers and to investigate correlates of their understanding. Subjects, Materials, and Methods: A total of 193 patients with newly diagnosed advanced lung cancer and their 167 caregivers were enrolled at 16 hospitals in Japan. We assessed their perceptions of prognosis and goals of therapy and examined their associations with their sociodemographic characteristics, clinical status, quality of life, mood symptoms, and the status of disclosure of information by their treating physicians. Results: One fifth of patients and caregivers (21.7% and 17.6%, respectively) mistakenly believed that the patients’ cancer was “completely curable.” Substantial proportions of them (16.9% and 10.3%, respectively) mistakenly believed that the primary goal of therapy was to remove all the cancer. Levels of anxiety and depression in both patients and caregivers were significantly higher among those who had accurate understanding of prognosis. In multivariate analyses, inaccurate perceptions of prognosis in patients were associated with sex, better emotional well-being, and lower lung cancer-specific symptom burden. Caregivers’ inaccurate perceptions of patients’ prognoses were associated with better performance status and better emotional well-being of patients. Conclusion: Substantial proportions of advanced lung cancer patients and their caregivers misunderstood their prognosis. Interventions to improve their accurate prognostic understanding should be developed with careful attention paid to its associated factors. Implications for Practice: This study demonstrated that substantial proportions of patients with newly diagnosed advanced lung cancer and their caregivers had misunderstandings about their prognosis. Accurate perceptions of prognosis, which are indispensable in the delivery of effective care, were associated with elevated levels of anxiety and depression in both patients and caregivers, warranting psychosocial care and support for them immediately after diagnosis. Inaccurate perceptions of prognosis in patients were associated with better emotional well-being and lower lung cancer-specific symptom burden. Illness understanding in caregivers was associated with patients’ physical and mental status. Those findings provide insight into how they obtain accurate illness understanding.
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