The MAMA-MIA Challenge: Advancing Generalizability and Fairness in Breast MRI Tumor Segmentation and Treatment Response Prediction. - Lidia Garrucho; Smriti Joshi; Kaisar Kushibar; Richard Osuala; Maciej Bobowicz; Xavier Bargalló; Paulius Jarusevicius; Kai Geissler; Raphael Schäfer; Muhammad Alberb; Tony Xu; Anne L. Martel; et al. (CoRR, 2026)