  Estrogen receptor positive breast cancer is frequently treated with
anti-hormonal treatment such as aromatase inhibitors (AI). Interestingly, a
high body mass index has been shown to have a negative impact on AI efficacy,
most likely due to disturbances in steroid metabolism and adipokine production.
Here, we propose a mathematical model based on a system of ordinary
differential equations to investigate the effect of high-fat diet on tumor
growth. We inform the model with data from mouse experiments, where the animals
are fed with high-fat or control (normal) diet. By incorporating AI treatment
with drug resistance into the model and by solving optimal control problems we
found differential responses for control and high-fat diet. To the best of our
knowledge, this is the first attempt to model optimal anti-hormonal treatment
for breast cancer in the presence of drug resistance. Our results underline the
importance of considering high-fat diet and obesity as factors influencing
clinical outcomes during anti-hormonal therapies in breast cancer patients.
