Photodynamic therapy (PDT) is an alternative treatment for cancer that involves the administration of a photosensitizing agent, which is activated by light at a specific wavelength. This illumination causes after a sequence of photoreactions, the production of reactive oxygen species responsible for the death of the tumor cells but also the degradation of the photosensitizing agent, which then loose the fluorescence properties. The phenomenon is commonly known as photobleaching process and can be considered as a therapy efficiency indicator. Methods: This paper presents the design and validation of a real time controller able to track a preset photobleaching trajectory by modulating the light impulses width during the treatment sessions. Results:This innovative solution was validated by in vivo experiments that have shown a significantly improvement of reproducibility of the inter-individual photobleaching kinetic. Conclusion: We believe that this approach could lead to personalized photodynamic therapy modalities. Significance: This work may open new perspectives in the control and optimization of photodynamic treatments.