Dosimetric comparison of treatment plans with field-in-field and intensity modulated techniques for radiotherapy of glioblastoma multiforme tumors

Objective: The aim of this study was dosimetric comparison of field-in-field and intensity modulated radiation therapy techniques in patients diagnosed with glioblastoma multiforme (GBM) in the Department of Radiation Oncology of Akdeniz University Faculty of Medicine, Method: The computed tomography (CT) images of 16 patients who were diagnosed and treated with GBM were used. Target volume (PTV) definitions were made for doses of 46 and 60 Gy. The critical organ (OAR) volumes were contoured according to the international criteria. Plans were established for each patient with field-in-field (FIF) and intensity modulated radiotherapy (IMRT) technique. Dose volume histogram for PTV and OARs was obtained, dose homogeneity index (HI) and dose conformity index (CI) parameters were calculated and statistical comparison between techniques was performed. The effect of the target volume position was evaluated statistically in two planning techniques. Results: The IMRT technique was found to be superior to the HI and V46 parameters of PTV46 plans. For PTV60, D95 and Dmean values were more suitable for FIF plans. However, parameter V60 was found to be better in the IMRT plans. Dmean, D2 and V50 of normal brain tissue; D2 and Dmax of right and left optic nerve tissue; Dmax values of chiasma tissue were lower in FIF plans. However, the Dmean value for brainstem tissue was lower in IMRT plans. MU values and average number of segments were lower in FIF plans. Conclusion: In dosimetric comparison of two planning techniques in GBM radiotherapy, FIF technique is considered superior in terms of HI and CI parameters, low MU data, low segment number and low risk organ doses. In GBM treatment planning, it is recommended to design plans with FIF technique according to dosimetric criteria first of all. In middle-placed tumors, the design of the plans is recommended with IMRT technique. Key words: Field in Field, Glioblastoma multiforme, Radiotherapy, Three dimensional radiotherapy, Intensity modulated radiotherapy