Mendes, R. V.; Ribeiro, J.; Gouveia, H.; Almeida, C. R. d.; Castillo-Martin, M.; Brito, M. J.; Canas-Marques, R.; Batista, E.; Alves, C.; Sousa, B.; Gouveia, P.; Ferreira, M. G.; Cardoso, M. J.; Cardoso, F.; Fior, R.

Chemotherapy remains the mainstay in most high-risk breast cancer (BC) settings, with several equivalent options of treatment. However, the efficacy of each treatment varies between patients and there is currently no test to determine which option will be the most effective for each individual patient. Here, we developed a fast in-vivo test for BC therapy screening: the zebrafish patient derived xenograft model (zAvatars), where in-vivo results can be obtained in just 10 days. To determine the predictive value of the BC zAvatars we performed a clinical study, where zAvatars were treated with the same therapy as the donor-patient and their response to therapy was compared. Our data shows a 100% correlation between patient\'s clinical response to treatment and its matching zAvatar. Altogether, our results suggest that the zAvatar model constitutes a promising in-vivo assay to optimize cancer treatments in truly personalized manner.