This Open Access book constitutes the refereed proceedings of the First MICCAI Challenge, HNTSMRG 2024, Held in Conjunction with MICCAI 2024, in Marrakesh, Morocco, on October 17, 2024. The 20 full papers and 1 overview paper included in this volume were carefully reviewed and selected from a total of 21 submissions. The HNTS-MRG 2024 Challenge focuses on advancing clinical workflows by leveraging artificial intelligence (AI) for automated segmentation of tumor regions in multi-timepoint MRI scans.