This manuscript introduces a theoretical model to study the problem of heat and mass transfer in biological tissues in a magnetic field, which simulates cancer treatment using thermal therapy. In particular, this model incorporates the influence of the Brownian motion and thermal thermophoresis of nanoparticles. Firstly, the non-linear governing equations of motion are transformed into ordinary differential equations using similarity transformations, then solved numerically according to appropriate boundary conditions using MATLAB built-in solver bvp4c. All parameters and their impacts on the flow have been investigated and studied. The model predictions showed that increasing the heat absorption by nanoparticles in the tissue increases the tumour temperature, which helps to improve the therapeutic efficiency and reduce the concentration of nanoparticles. Hence, the results of this study could enhance the effectiveness of thermal therapy for malignancies.