Background: Consolidating treatment with immunotherapy for patients with locally advanced lung cancer has improved survival dramatically. Immunotherapy is administered once monthly for a year after concomitant chemoradiotherapy, involving new symptom experiences and prolonging total treatment length. In transitioning from chemoradiotherapy and during consolidating treatment, little is known about what support patients need and how needs change over time. As immunotherapy extends survival and treatment length, patients increasingly face existential concerns. Aim: To identify vulnerabilities through boundary situations during consolidating immunotherapy in patients with locally advanced lung cancer. Method: Seventeen patients were interviewed about their experiences of undergoing treatment with immunotherapy. The interviews were analyzed deductively, using an analytical matrix based on the existential framework of Yalom and Binder; Death, Meaninglessness, Freedom, Isolation and Body. The results were reviewed for Boundary situations, where a person is exposed to the harshest circumstances of existence. Results: Four contexts where patients face boundary situations were identified: when abiding mortality, in re-orientations, when partnering with healthcare professionals and in guilt and responsibility. Abiding mortality comprises situations where patients face a heightened sense of mortality and immunotherapy as protection against death. Re-orientations refers to situations where patients need to re-negotiate their future, bodily capabilities, relationships and faith. Partnership with healthcare professionals encompasses existential tensions in healthcare contacts, control, abandonment and the healthcare system as a map of meaning. Guilt and responsibility relate to guilt over past choices and guilt from reduced ability to partake in social activities and how delegated responsibility and participation in medical decisions become difficult to bear. Discussion: The identified boundary situations overlap and interact. Understanding the overlaps can prove useful for health care professionals when using a person-centred framework of care. By recognizing the boundary situations, support to patients can be initiated in time and be more in line with patients needs.