New insights into photodynamic therapy of the head and neck

Photodynamic therapy (PDT) is a young method, which uses a combination of a light sensitive substance (photosensitizer) and visible light, to treat tumors. This thesis analyses the clinical efficacy of PDT in the head and neck area and introduces methods to improve the clinical results and broaden the treatment spectrum. The second chapter demonstrates that PDT is comparable to surgery of the early stage tumors of the oral cavity. The third chapter analyses the treatment success of PDT with regards to tumor location, size and previous treatments. Chapters 3-6 describes a new non-invasive spectroscopic method, fluorescence differential pathlength spectroscopy (FDPS), which gives information about two major components of PDT: oxygen and photosensitizer concentration in treated tissues. By incorporating FDPS into clinical practice it is possible to detect correctable errors during PDT, which potentially will result in improvement of the treatment. Chapters 7 and 8 introduces a treatment method to treat larger tumors using PDT. One of the limitations of PDT is that light can penetrate a limited distance into tissues. By implanting light sources in the tumors (interstitial PDT (iPDT)) this limitation can be overcome. Early experiences with this method is promising. A new treatment protocol to standardize iPDT is described in this thesis.