Objective: Despite its approval in 2004 PDT has not well established in the palliative tumour therapy of head neck cancers (HNC). Furthermore we have no diagnostic and therapeutic standards for this procedure.
Material and methods: We performed a retrospective analysis of the treated HNC patients of ORL department Nordhausen between 11-2016 and 10-2018 in order to develop practical standards for daily practice, and to describe new projects of research. We analyzed the data of 35 patients with histological confirmed squamous cell carcinoma. The patients have got 1 mg/kg Chlorin E6 IV. Then we performed PD in optical and/or spectroscopical (405 nm) technique. The application was corrected, and the PDT was done by a red-light system (670 nm).
Results: We treated 9 malignancies of the tongue/mouth, 9 laryngeal cancer, 7 malignancies of nose/paranasal sinus, 4 cancer of palatal and buccal region, and 3 pharyngeal cancers. Aims of PDT were 33times tumour reduction, and twice decrease of symptom burden. The follow-up interval was median 5 month (range 1-30); 24 patients are alive, 8 patients died, 3 were lost in follow up. We performed median 2 PDT per patient (range 1-19). The application technique was interstitial in 12 patients, frontal in 10 patients and cylindric in 13 patients. PDT was performed as only therapy in 15 patients, in multimodal combinations in 20 patients. We have registered 14 CR, 10 PR, 10 SD and 1 PD.
Conclusion: PDT is an effective procedure to get local control in palliative situation of HNC.
Fiber-coupled 405 nm diode laser systems are rarely used with fiber output powers higher than 50 mW. A quick degradation of fiber-coupled high power modules with wavelengths in the lower range of the visible spectrum is known for several years. Meanwhile, the typical power of single-mode diode lasers around 400 nm is in the order of 100 to 300 mW, leading to single-mode fiber core power densities in the 1 MW/cm<sup>2</sup> range. This is three magnitudes of order below the known threshold for optical damage. Our profound investigations on the influence of 405 nm laser light irradiation of single-mode fibers found the growth of periodic surface structures in the form of ripples responsible for the power loss. The ripples are found on the proximal and distal fiber end surfaces, negatively impacting power transmission and beam quality, respectively. Important parameters in the generation of the surface structures are power density, surface roughness and polarization direction. A fiber-coupled high-power 405 nm diode laser system with a high longterm stability will be introduced and described.