Near infrared low-level laser effect on electron radiation therapy of non-melanoma human squamous cell cancer: An in-vitro study

Purpose: The aim is to assess the efficacy of combined electron-laser radiation therapy on non-melanoma Squamous cell carcinoma (SCC) cancer cells in an in-vitro model. Material and methods: The human SCC cancer line (TSCC-1) was purchased from the Iranian Biological Resources Center (IBRC) and cultured according to the standard protocol. The groups of this study were control; only electron radiation; only Low-Level Laser Therapy (LLLT); and combined laser-electron radiation. Irradiation with a 980 nm 50 mW laser was performed in a single session with energy doses of 1 and 1.5 J/cm(2). Electron radiation was carried out using a Varian accelerator with a radiation dose of 2 and 4 Gy. 24 h after laser treatment of cancer cells, combined electron irradiation was performed. MTT and flow cytometry bioassays were performed and analyzed to check their effectiveness. Results: The cell viability assay for irradiation with 980 nm 50 mW NIR laser in a single session with an irradiation time of 20 and 30 s in combination with 2 and 4 Gy electrons showed a significant difference (P-value <0.01). Flow cytometry test of the electron-radiated samples showed that the sum of early and late apoptosis was the highest. However, for the combination of electron-laser radiation of 30 s with 2 and 4 Gy electrons, the maximum percentage of apoptosis and necrosis was obtained close to the electron alone. Except for the control group, the quantitative interval of induced necrosis of all the groups evaluated by electron alone, laser alone, and combined electron laser was almost equivalent. Conclusions: This study showed that the physical parameters of a 980 nm NIR LLLT might not have a synergy effect on treatment response in combination with an electron ionizing beam on SCC cancer cells. It is critical to consider the effect of light irradiation parameters for combination therapy in more extensive studies.