Abstract
AbstractObjectiveThis study aimed to compare the dose distribution and delivery to organs at risk between five‐ and seven‐beam intensity‐modulated radiotherapy (IMRT) and volumetric‐modulated arc radiotherapy (VMAT) for preoperative rectal cancer. The characteristics of the rectal cancer target were analyzed, and the outcomes of the different modalities were evaluated. This research could provide a reference for the selection of treatment modalities in rectal cancer radiotherapy.MethodsThree different treatment plans were used, namely five‐beam IMRT, seven‐beam IMRT, and VMAT, to compare the dose‐volume histograms, conformal index, homogeneity index, and dose delivery to organs at risk.ResultsIn terms of conformal index, the VMAT plan was the best, and the seven‐beam plan was better than the five‐beam plan (0.88 vs 0.91 vs 0.92). The homogeneity indexes were 1.08, 1.06, and 1.08, respectively. Fixed‐field IMRT was better than VMAT in terms of homogeneity index (P < 0.05). No significant differences in maximum dose within targets were found among the three treatment plans. As for organs at risk, such as the bowel and femoral head, VMAT increased V10 and V20, but showed lower values for high‐dose volumes, including V30, V40, and V50. The volumes in the low‐ and high‐dose regions were lower when comparing between the VMAT and fixed‐field plans for dose delivery to the bladder. The VMAT plan decreased the volume delivered to >30 Gy, and less than five‐ and seven‐beam plans (14%, 19%, 17%).ConclusionsFor patients undergoing radiotherapy, five‐beam IMRT, seven‐beam IMRT, and VMAT could meet the requirement of clinical treatment. However, the three modalities showed many differences. Apart from the position and volume of the target, other parameters such as the movement and the priority of organs at risk (OAR) are also important. These OARs include the bladder. VMAT could be used to reduce the high‐dose volume and injury of bone marrow such as radioactive bone marrow suppression. IMRT could reduce the probability of suffering from diarrhea and other complications.
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