Biological Evaluation of Grid versus 3D Conformal Radiotherapy in Bulky Head and Neck Cancer

Grid radiotherapy is one of the treatment techniques applied to treat patients with advanced bulky tumors. PURPOSE: This study aims to estimate the difference in biological and dosimetric parameters of the grid radiotherapy technique for the treatment of bulky head and neck (H and N) tumors and compare it with conventional conformal radiotherapy. SUBJECTS AND METHODS: Three-dimensional conformal and grid radiotherapy were designed by the Monaco treatment planning system (TPS). Eight bulky tumors of (H and N) cases were selected, using a single fraction 15–20 Gy. Dose-volume histogram of the tumors and organs at risk (OARs) used to calculate the equivalent uniform dose (EUD) (Gy) by Matlab program. Furthermore, dosimetric parameters of the tumors from the TPS were compared for two techniques (grid radiotherapy and the conventional conformal radiotherapy). RESULTS: Grid attained a lower EUD (Gy) in tumors and OARs as compared to conformal therapy, as Grid principle protects about half of the tumor area from the radiation leads to less coverage of the tumor. Also, where OARs in closed with tumors and the shielding by multi-leaf (1 cm) were more effective than other techniques, lead to a decrease of radiobiological values according to its definition by Niemierko. Radiobiological results showed significant differences between the two methods, and dosimetric data obtained by the TPS for tumours for two plans were P < 0.05. CONCLUSIONS: The grid plan achieves lower values of EUDs than the conformal technique for OARs. Hence, it achieves more sparing and fewer complications for these organs.