Comparison of Volumetric Modulated Arc Therapy (VMAT) and Static Intensity Modulated Radiotherapy (IMRT) for Malignant Pleural Mesothelioma in Patients with Intact Lungs/post Pleurectomy
V DUMANE1*, E Yorke2, A Rimner3, K ROSENZWEIG4, (1) THE MOUNT SINAI MEDICAL CENTER,(2) Memorial Sloan-Kettering Cancer Center, New York, NY, (3) Memorial Sloan-Kettering Cancer Center, New York, NY, (4) THE MOUNT SINAI MEDICAL CENTER,SU-E-T-595 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: This planning study compares VMAT and static gantry, sliding window IMRT for malignant pleural mesothelioma for post pleurectomy.
Methods: We compared plans for a left sided (L) and a right sided case (R). Plans used clinically approved planning target volumes (PTVs) and critical organ contours. IMRT plans employed 7-8 6 MV photon beam directions over a 215º range centered on the ipsilateral lung. VMAT plans used 4 partial arcs within the same range and energy. Prescription dose per fraction was 1.8 Gy; case L went to 50.4 Gy, case R to 46.8 Gy. Planning objectives were: Lyman model NTCP for both lungs < 25%; contralateral lung, mean dose < 8 Gy; heart, V30 Gy < 50%, mean < 30 Gy; Each Kidney, V18 Gy < 33%; liver_not_GTV, mean < 30 Gy, V30 Gy < 50%; stomach_not_PTV, mean < 30 Gy; cord maximum < 45 Gy; bowel maximum < 55 Gy, D05 < 45 Gy; PTV D95 = 94%, V95 = 94%, D05 = 115%. Dose calculation was done with the AAA algorithm.
Results: : VMAT and IMRT both met the dosimetric constraints. The VMAT MU were 887 (L)_and 896 (R) and for IMRT were 1691 (L) and 2409 (R). IMRT required 14-16 fields (wide-field splitting). The delivery times were 8 minutes (VMAT) and 20 minutes (IMRT). For coverage and plan homogeneity parameters within 1.5% - 2%, VMAT better spared organs at risk.
Conclusions: Both VMAT and IMRT are feasible techniques for the treatment of malignant pleural mesothelioma with intact lungs, with less MU and a shorter delivery time for VMAT. Additional cases must be planned to test generality of our preliminary results.