Abstract RF1-06: Discordance in End-of-Life Decision-Making: A Quantitative Study on the Values and Preferences of Japanese Cancer Patients and Their Family Members

Abstract Background: While Advance Care Planning (ACP) is critical for respecting patient autonomy, a significant gap exists in the quantitative understanding of the specific discordance in values and preferences between Japanese cancer patients and their families. This study aimed to deconstruct these potential conflicts by moving beyond item-by-item comparisons to an analysis of their underlying conceptual structures. Methods: Self-administered questionnaires were distributed at Breast and Thyroid Center, Jyoban Hospital, from August 1, 2024, to May 31, 2025. A total of 470 outpatients with breast cancer and 324 family members responded to the survey. For the primary dyadic analysis, a final matched sample of 218 patients and their 324 family members was used. Descriptive statistics were first calculated for all variables. Generalized Linear Mixed-Effects Models (GLMM) were employed to examine differences in preferences while accounting for the one-to-many dyadic structure, with intraclass correlation coefficients confirming model appropriateness. Chi-squared tests with Bonferroni correction were used to analyze the association between preferences and the patient’s choice of surrogate. Multiple Correspondence Analysis (MCA) was then performed to identify the latent structures of “Life Priorities and Values” and “End-of-Life Care Preferences. Results: The initial descriptive analysis of the full 470-patient cohort revealed that "Independence in Activities of Daily Living (ADL)" (85.7%) and "Not being a burden to family" (76.4%) were the most frequently endorsed priorities. Within the dyadic sample, the most prevalent preference among family members was "Engagement in enjoyable and meaningful activities" (78.4%). Subsequent GLMM analysis confirmed significant discordance. Patients systematically prioritized autonomy and avoiding burden, with the odds of family members endorsing these values being substantially lower (e.g., for Independence in ADL, OR = 0.20, 95% CI [0.12, 0.34]; for Not being a burden to family, OR = 0.31, 95% CI [0.20, 0.48]; both p < .001). Conversely, families prioritized life prolongation and intervention, with the odds of endorsing "Longevity" being more than double those of patients (OR = 2.15, 95% CI [1.42, 3.24], p < .001) and the odds for "Receiving treatment until personal satisfaction is met" being 4.5 times higher (OR = 4.50, 95% CI [2.75, 7.37], p < .001). Subsequent GLMM analysis confirmed significant discordance. Patients systematically prioritized autonomy and avoiding burden (e.g., for Independence in ADL, OR for family vs. patient = 0.20), while families prioritized life prolongation and intervention (e.g., for Longevity, OR = 2.15; both p < .001). Furthermore, Chi-squared tests revealed that the designation of a spouse—but not a child—as a surrogate was significantly linked to distinct preference patterns. For instance, the choice of a spouse was significantly associated with the preference for "Prognostic awareness" within both the patient cohort (Cramér's V = 0.25, p < .001) and the family cohort (Cramér's V = 0.15, 95% CI [0.04, 0.26], p = .009). Crucially, MCA visualized this fundamental structural divergence: on a map of values, patients were oriented towards "self-reliance and not being a burden," while families were oriented towards "survival, even with dependency." Conclusion: This study is one of the first in Japan to quantitatively reveal, through dyadic modeling and conceptual mapping, that patients prioritize social independence and dignity, while families emphasize life preservation—a structural gap likely contributing to clinical conflict. Effective ACP should move beyond treatment choices and promote deeper dialogue to bridge these underlying worldviews and truly honor patient values. Citation Format: A. Ozaki, K. Gonda, A. Hara, A. Ajitomi, M. Wada, K. Tachibana, M. Arai, K. Konuma, T. Sawano, Y. Kanemoto, H. Miyatake, T. Kurokawa, Y. Kouchi, N. Kanzaki, Y. Kotera, Y. Takebayashi, M. Murakami, T. Ohtake, H. Shimmura. Discordance in End-of-Life Decision-Making: A Quantitative Study on the Values and Preferences of Japanese Cancer Patients and Their Family Members [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr RF1-06.