Dosimetric comparison of intensity modulated arc therapy and robotic-ARM radiosurgery techniques in early stage glottic larynx radiotherapy

In this study, 15 EGL cases previously treated with standard dose/fraction schemes in our institute, it was aimed to statistically investigate the treatment plans of EGL patients which had been re-obtained with hypofraction schemes, using Intensity Modulated Arc Radiotherapy (IMAT) and Stereotactic Body Radiation Therapy with Robotic Arm (RA-SBRT) techniques, in terms of Conformity Index (CI), Homogenity (HI), Monitor Unit (MU), PTV and organ at risk doses. The 3-D images required for treatment planning were taken from the archives of the İ.Ü Institute of Oncology and were uploaded to the treatment planning system. 4.5 Gy was defined per fraction and a total of 10 fracture treatment doses were planned. The treatment dose is aimed to cover at least 95% of the PTV volume. Lymph node irradiation was not performed. Maximum dose (Dmax), minimum dose (Dmin) values of PTV treatment volumes as well as average dose (Dmean) comparisons were made. In the evaluation of PTV volume, IMAT technique was found to have statistically significantly more appropriate Dmax, Dmean dose values and HI values compared to RK-SBRT technique(p<0,05). There was no statistically significant difference between the techniques in the evaluation of CI values. RA-SBRT technique, statistically significant lower spinal cord Dmax values than IMAT technique were obtained(p<0,05). statistically significant lower carotid artery with Dmean and Dmax values were obtained by IMAT technique (p<0,05). Thyroid gland Dmean values were also significantly lower than RA-SBRT technique(p<0,05). The higher MU values were obtained with RA-SBRT technique compared to IMAT technique. Developments in radiotherapy techniques and radiobiology, it allows the daily high treatment doses to be given in low fraction. This study, which compared SBRT techniques in the treatment of EGL cancer, IMAT technique was found to be more appropriate than RA-SBRT technique in terms of treatment volume dose evaluation, thyroid gland, carotid artery and MU values, except spinal cord Dmax values. Key Words: IMAT, RA-SBRT, Early-Stage Glottic Larynx