(1) Background: Studies examining the psychosocial impact of living long term on systemic treatment in advanced cancer patients are scarce. This scoping review aimed to answer the research question “What has been reported about psychosocial factors among patients living with advanced cancer receiving life-long systemic treatment?”, by synthesizing psychosocial data, and evaluating the terminology used to address these patients; (2) Methods: This scoping review was conducted following the five stages of the framework of Arksey and O’Malley (2005); (3) Results: 141 articles published between 2000 and 2021 (69% after 2015) were included. A large variety of terms referring to the patient group was observed. Synthesizing qualitative studies identified ongoing uncertainty, anxiety and fear of disease progression or death, hope in treatment results and new treatment options, loss in several aspects of life, and worries about the impact of disease on loved ones and changes in social life to be prominent psychosocial themes. Of 82 quantitative studies included in the review, 76% examined quality of life, 46% fear of disease progression or death, 26% distress or depression, and 4% hope, while few studies reported on adaptation or cognitive aspects. No quantitative studies focused on uncertainty, loss, or social impact; (4) Conclusion and clinical implications: Prominent psychosocial themes reported in qualitative studies were not included in quantitative research using specific validated questionnaires. More robust studies using quantitative research designs should be conducted to further understand these psychological constructs. Furthermore, the diversity of terminology found in the literature calls for a uniform definition to better address this specific patient group in research and in practice.