Background <p>In the context of medically futile treatment, clinical decision-making often becomes ethically and existentially fraught, especially when physicians and patients navigate the space between prolonging life and preserving its meaning. Existing shared decision-making (SDM) models often rely heavily on empirical rationality, yet overlook the ontological depth of patient experience.</p> Methods <p>Drawing on Heidegger’s concept of <i>being-in-the-world</i> and Gadamer’s <i>fusion of horizons</i>, we conducted an interpretative phenomenological analysis (IPA) of in-depth interviews with a terminal cervical cancer patient and three attending physicians (specialists in cardiology, cardiac surgery, and gynecologic oncology). These philosophical frameworks guided both the analytic lens and the ethical interpretation of SDM practices in contexts of medical futility.</p> Results <p>Our findings reveal that decisions to continue aggressive treatment, even when medically futile, are not mere irrationalities. Rather, they emerge from divergent value orientations and temporal understandings between patients and physicians. A clinically “correct” decision may be ethically inadequate if it fails to integrate the patient’s lived horizon.</p> Conclusions <p>We propose a hermeneutic framework for SDM that supplements the evidence-based model with three core steps: attunement to the patient’s existential situation, fusion of horizons between patient and physician, and respect for irreducible differences. This approach allows for ethically grounded decisions that honor both medical expertise and the patient’s being-in-the-world.</p> Trial registration <p>Not applicable.</p>