In silico modelling of apoptosis induced by photodynamic therapy

Photodynamic therapy using topical toluidine blue for the treatment of oral leukoplakia: A prospective case series

BACKGROUND

Photodynamic therapy (PDT) is a minimally invasive method for the treatment of oral leukoplakia (OL) through the activation of a photosensitizer, after exposure to a specific wavelength light source.

METHODS

To investigate the effectiveness of toluidine blue as topical photosensitizer. Eleven patients participated in this study; fifteen oral leukoplakia lesions were treated, in several sessions, with 2.5 % toluidine blue and an LED source of 630 nm wavelength. Patients were evaluated at baseline (t0), at the end of treatment cycles (t1) and one year from the end of treatment (t2). All the treated sites were photographed at each visit. Images were processed with ImageJ 1.52 software in order to obtain the areas (mm2) of the treated lesions. Comparison between data at different follow-up was performed using a paired T-test.

RESULTS

At t1, complete response was obtained in six lesions, partial response in seven lesions while only two lesions showed no response. At t2, a further improvement was observed in two patients. The analysis of the areas showed significant reduction of the lesion size from t0 to t1 (p = 0.003), and from t1 to t2 (p = 0.01).

CONCLUSION

Toluidine blue appears to be a promising photosensitizer in the photodynamic therapy of oral leukoplakia.

Illuminating the Numbers: Integrating Mathematical Models to Optimize Photomedicine Dosimetry and Combination Therapies

Cancer photomedicine offers unique mechanisms for inducing local tumor damage with the potential to stimulate local and systemic anti-tumor immunity. Optically-active nanomedicine offers these features as well as spatiotemporal control of tumor-focused drug release to realize synergistic combination therapies. Achieving quantitative dosimetry is a major challenge, and dosimetry is fundamental to photomedicine for personalizing and tailoring therapeutic regimens to specific patients and anatomical locations. The challenge of dosimetry is perhaps greater for photomedicine than many standard therapies given the complexity of light delivery and light-tissue interactions as well as the resulting photochemistry responsible for tumor damage and drug-release, in addition to the usual intricacies of therapeutic agent delivery. An emerging multidisciplinary approach in oncology utilizes mathematical and computational models to iteratively and quantitively analyze complex dosimetry, and biological response parameters. These models are parameterized by preclinical and clinical observations and then tested against previously unseen data. Such calibrated and validated models can be deployed to simulate treatment doses, protocols, and combinations that have not yet been experimentally or clinically evaluated and can provide testable optimal treatment outcomes in a practical workflow. Here, we foresee the utility of these computational approaches to guide adaptive therapy, and how mathematical models might be further developed and integrated as a novel methodology to guide precision photomedicine.

Photodynamic therapy: Toward a systemic computational model

We have designed a systemic model to understand the effect of Photodynamic Therapy (PDT) on long time scales. The model takes into account cell necrosis due to oxygen reactive species, cell apoptosis through the caspase pathway and the competition between healthy and tumor cells. We attempted to describe the system using state of the art computational techniques (necrosis and apoptosis) and simple models that allow a deeper understanding of the long time scale processes involved (healing and tumor growth). We analyzed the influence of the surface and tumor depth on the effectiveness of different treatment plans and we proposed, for the set of parameters used in this work, an optimum timing between sessions of PDT.