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A Dosimetric Comparison of Volumetric Modulated Arc Therapy and Tomotherapy with Simultaneous Integrated Boost for Rectal Cancer

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T Sun

T Sun*, l XiuTong , Y Yin , Shandong Cancer Hospital Affiliated to Shandong University,Shandong Cancer Hospital, Jinan, Shandong


SU-I-GPD-T-337 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare the dosimetric differences among volumetric-modulated arc therapy (VMAT) and tomotherapy(HT) plans with simultaneous integrated boost in rectal cancer.

Methods: Ten patients with rectal cancer previously treated with IMRT were included in this analysis. For each patient, two treatment techniques were designed for each patient: the double-arc VMAT with RapidArc technique and tomotherapy plan. The treatment plan was designed to deliver in one process with simultaneous integrated boost (SIB). The prescribed doses to the planning target volume of the subclinical disease (PTV1) and the gross disease (PTV2) were 45 Gy and 55 Gy in 25 fractions, respectively. The dose distribution in the target, the dose to the organs at risk, total MU and the delivery time in two techniques were compared to explore the dosimetric differences.

Results: For the target dose, conformity and homogeneity in PTV1 and PTV2, no statistically differences were observed in the two plans. VMAT plans reduced the mean dose to bladder and iliac wings compared to HT plans. HT plans reduced the small bowel irradiated volume of 10Gy. No statistically differences were observed in the dose of femur heads among the two plans. Compared with HT plans, VMAT plans showed a significant reduction of monitor units by nearly 20% and reduced treatment time by an average of 65%.

Conclusion: Compared to VMAT plans, HT plans showed the similar target dose and reduced the dose of small bowel for rectal cancer. VMAT plans showed a significant advantage in the number of monitor units and the treatment time.

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