The Belgian Approach for Local Laboratory Extensive Tumor Testing (BALLETT) study assessed the feasibility of using comprehensive genomic profiling (CGP) in clinical decision-making for patients with advanced cancers. This multi-center study enrolled 872 patients from 12 Belgian hospitals. CGP was performed on tumor tissues using a standardized CGP panel (523 genes) across nine laboratories with success in 93% of patients and a median turnaround time of 29 days. Actionable genomic markers were identified in 81% of patients, substantially higher than the 21% using nationally reimbursed, small panels. A national molecular tumor board (nMTB) recommended treatments for 69% of patients, with 23% receiving matched therapies. Reasons for non-compliance were highly variable across clinical sites. Overall, BALLETT demonstrates the feasibility of implementing decentralized CGP and its potential to identify actionable targets in most patients with advanced cancers. BALLETT reinforces CGP's utility and emphasizes the importance of collaboration, standardization, and addressing implementation challenges.