Radiation treatment planning for prostate cancer: A new dosimetric comparison of five and seven fields IMRT plans

Background: To compare the dosimetric coverage of the planning target volume (PTV) and the dose delivered to the main Organs at Risk (OARs) in 5 and 7-field techniques of Intensity Modulated Radia%on Therapy (IMRT) in pa%ents with local prostate cancer. Materials and Methods: Twelve pa%ents with local prostate cancer underwent 5 and 7-field IMRT planning. The delivery of IMRT was carried out using the sliding technique. The dose coverage for PTV was designated to ≥98% of the PTV covered by 95% of the prescribed dose. Dose conformity was evaluated by comparing the volume of nontarget %ssue receiving maximum, and average of the prescribed dose and the dose of 33%, 50%, and 66% of the volumes on both planning sets. For target, this evalua%on was made with comparing the Conformity Index (CI) and Inhomogeneity Index (HI). In addi%on, we compared the monitor units used for dose delivery in both planning techniques. Results: All the 5 and 7field IMRT plans differed slightly in the measured parameters, and none of them have sta%s%cally significant differences with each other except for the monitor units where significant differences were observed in favor of the 5field IMRT plans (p=0.000). In all of the 5-field IMRT plans the mean dose delivered to OARs were very similar or less than that of the 7-field plans. Conclusion: In comparison to the 7-field technique, the 5-field IMRT technique has resulted in improved IMRT dose conformity, homogeneity, and lesser MUs used for radia%on therapy. However, this difference was not