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Dosimetric and Volumetric Modulation Using Helical TomoTherapy Planning for Malignant Pleural MesotheliomaTumors

A Movahed*, B Rabbani , X Zhu , T Lau , R Rao , S Gorty , Pomona Valley Hospital M. C., Pomona, CA

Presentations

SU-E-T-559 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
The purpose of this study is to come up with the most desirable and achievable target dose and OAR sparing using helical TomoTherapy planning system based on the earlier conducted studies.

Methods:
Patient having mesothelioma with mediastinal nodes was planned using helical TomoTherapy with Gross tumor volumes (GTVs) outlined were investigated: The goal was (1) keeping the prescribed dose to the targets while reducing the dose to the OARs and (2) escalating the target dose while maintaining the original level of healthy tissue sparing.

Results:
The primary lesion and nodal mass were kept at 98.7% of the dose and planning target volume (PTV) margins of 3 mm inner and 1cm outer with the planned mean of 94% volume to 54 Gy. Mean lung dose is 15.6 Gy, V5Gy:33%, V20Gy:30.1%, with contralateral lung V5Gy:0.87% Heart V45:26.2%, PTV V54Gy:90.5%, Pitch: 0.43 and Modulation factor: 1.66

Conclusion:
Based on many studies on the comparison of 3DCRT, IMRT and TomoTherapy, it is recommended that helical TomoTherapy provide better target coverage and sparing of OARs. Our data proved better PTV coverage. We planned a target dose of 54Gy but our institute would recommend re-evaluation at 45Gy. Helical TomoTherapy is a promising technique in the multimodality treatment of malignant pleural mesothelioma.
Unlike other studies where low doses received by the contralateral lung appear to be the limiting factor, we found using helical TomoTherapy the contralateral to be minimal V5Gy:0.87%.

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