We have used the AGAMENON-SEOM registry (NCT04958720) to develop a predictive model of PFS and OS specific to patients with a HER2+ AGA. The model has been externally validated in a cohort at the Christie Hospital in Manchester. To build this online calculator, we used a log-normal accelerated failure time model, as the aim was to model the mean time to PFS/OS, which is achieved as a semi-parametric model. In AFT models, survival times are multiplied by a constant effect under this formulation, so that the exponentiated coefficients are called time ratios (TR). A TR of more than 1 for the covariate implies that the covariate slows down or lengthens the time to the event, while a TR of less than 1 indicates that an event is more likely to occur earlier. Non-linear effects were modelled using restricted cubic splines.