Europe still sees a quarter of the world's cancer cases each year, making cancer the second leading cause of death and illness in the region after cardiovascular diseases. Unless we take decisive action, lives lost to cancer in the EU are set to increase by more than 24% by 2035, making it the leading cause of death in the EU. Cross-border collaboration can address this challenge by combining data from various modalities and sources, extracting meaningful insights to deepen our understanding of cancer. However, ethical, legal, and national regulations, along with data access processes, including differing interpretations of the EU GDPR create significant hurdles. Technical interoperability issues across European cancer RIs, and patients' and citizens' rights to control who uses their personal information and for what purposes further complicate data sharing. The project will provide European researchers, SMEs, and innovators with a decentralized collaborative network, “UNCAN-CONNECT,” for cancer research. It consists of both technical components, a governance, compliance, and operational framework based on the UNCAN blueprint, with the goal of operationalizing it. The objective is to facilitate access to cancer data, promote open science, and revolutionize cancer research and treatment by co-creating an open-source federation of federations platform. It will be developed using specific use cases focused on six major cancer types: Paediatric, Lymphoid malignancies, Pancreatic cancer, Ovarian, Lung, and Prostate cancers and active collaboration with a diverse range of stakeholders, including researchers, SMEs, industrial end users, and citizens. It will build on existing European RIs such as BBMRI as well as initiatives like EOSC4CANCER, CanSERV, EUCAIM, to enable seamless storage, access, sharing, and processing of data across Member States and associated countries. This approach will foster interoperability and collaboration, accelerating progress in cancer research. This action is part of the Cancer Mission clusters of projects 'Understanding' established in 2022.