Allogeneic hematopoietic cell transplantation (alloHCT) and chimeric antigen receptor T (CAR T)-cell therapy represent established therapeutic modalities for selected hematologic malignancies but are associated with substantial morbidity, high healthcare costs, and a considerable risk of severe complications, including death. This necessitates specialized and continuous post-treatment care, which is currently insufficiently standardized and still largely delivered predominantly through in-person and nonintegrated processes. We aimed to develop a comprehensive and innovative post-treatment care program for patients after alloHCT and CAR T-cell therapy based on an interdisciplinary, digitally supported, cross-regional and, cross-sectoral approach, and to evaluate its effectiveness in a randomized controlled trial (RCT). Developed by a multidisciplinary team, the intervention involves case managers and home visits by onco nurses, supported by digital components. These include patient-reported monitoring of vital signs and symptoms via a mobile application, video consultations, and virtual case conferences with community-based hematologists. The evaluation of effectiveness includes both quantitative outcomes, such as mortality and rehospitalization rates, and qualitative data derived from semi-structured interviews. The required ethics approvals were obtained in due time, and the three study centers were successfully initiated in 2024. As of January 2026, recruitment has been completed, and a total of 306 patients were successfully enrolled and randomized in a 1:1 ratio to receive either the SPIZ intervention or routine care. Funded and supported by the Federal Joint Committee (G-BA), a positive evaluation could facilitate the integration of the proposed care model into routine clinical practice, thereby strengthening post-treatment care for patients undergoing cellular therapy across Germany.