Language Select
Varian Logo

VARIAN MEDICAL AFFAIRS

Engaging with clinicians around the world to exchange meaningful information and advance clinical research.

VMAT1

Rx: 40Gy/15fx also 48Gy to Lumpectomy PTV (Simultaneous Integrated Boost)

RTOG 1005 Arm2-hypofractionation

1:42 VMAT treatment arc delivery time

Beams
DVH
Metrics

Name (ID): ROQS-25, Breast-Simple (ROQS-25)
Plan or PlanSum ID: RTOG1005a2VF5

 

Structure ID Structure Code Patient Structure DVH Objective Evaluator Variation Priority Met Achieved
BREAST PTV EVAL   PTVBreastEval40G V38.0Gy[%] >=95     Goal 99.06 %
BREAST PTV EVAL   PTVBreastEval40G V36.0Gy[%] >=90     Goal 99.92 %
BREAST PTV EVAL   PTVBreastEval40G V48.0Gy[%] <=30 35   Goal 10.64 %
BREAST PTV EVAL   PTVBreastEval40G D50.0%[Gy] <=43.2 44.8   Goal 42.106 Gy
WHOLE BREAST   PTV Breast - PTV Max[Gy] <=46 48   Goal 44.582 Gy
LUMPECTOMY PTV EVAL   PTVLumpEval V45.6Gy[%] >=95     Goal 96.62 %
LUMPECTOMY PTV EVAL   PTVLumpEval V43.2Gy[%] >=90     Goal 100.00 %
LUMPECTOMY PTV EVAL   PTVLumpEval V52.8Gy[%] <=5 10   Goal 0.00 %
LUMPECTOMY PTV EVAL   PTVLumpEval Max[Gy] <=55.2 57.6   Goal 52.382 Gy
CONTRALATERAL BREAST   CONTRA_BREAST Max[Gy] <=2.4 3.84   Variation 3.567 Gy
CONTRALATERAL BREAST   CONTRA_BREAST D5.0%[Gy] <=1.44 2.4   Variation 1.615 Gy
IPSILATERAL LUNG   IPSILATERAL_LUNG V16.0Gy[%] <=15 20   Goal 12.17 %
IPSILATERAL LUNG   IPSILATERAL_LUNG V8.0Gy[%] <=35 40   Goal 29.62 %
IPSILATERAL LUNG   IPSILATERAL_LUNG V4.0Gy[%] <=50 55   Goal 48.14 %
CONTRALATERAL LUNG   CONTRA_LUNG V4.0Gy[%] <=10 15   Goal 4.72 %
HEART   HEART V8.0Gy[%] <=10 15   Goal 4.12 %
HEART   HEART Mean[Gy] <=3.2 4   Goal 2.753 Gy
THYROID   THYROID Max[Gy] <=0.96 1.44   Goal 0.618 Gy
Technical Plan Comments

The plan consists of four (4) partial arcs set to begin just at the most medial aspect of the contralateral breast until 15 degrees from PA.  The arcs’ unique collimator rotations were generated using the arc geometry tool.

Targets were defined as per RTOG1005.  Ultimately the Lumpectompy PTV was used for optimization along with the BreastPTVeval with a 1cm expansion anteriorly and laterally (which consisted of .5cm expansion into air) called BreastPTVEvalOpt.  A 1cm virtual bolus was created in Eclipse to provide density for the Photon Optimizer to dose the portion of the BreastPTVEvalOpt structure which extended beyond the patient’s Body contour.  The obvious intention of this method was to create a VMAT plan which also provides .5cm of flash beyond the patient’s breast throughout the arc rotation.  After optimization, the virtual bolus was unlinked from the plan and the dose was calculated (intermediate dose was not utilized).

 To reach the planning goals of RTOG1005 arm2, higher than standard optimization priorities had to be placed to control the low dose to the heart, ipsilateral lung and the contralateral breast.  There is usually a direct relationship between fully meeting the maximum point dose metric to contralateral breast and meeting the low dose sparing criteria in the ipsilateral lung (V4) and heart mean dose constraints.  All protocol goals were met with minor deviations sited for the contralateral breast only.

With traditional C arm linear accelerators, static field IMRT is often employed for this SIB breast technique, as collimator rotations can be selected per field and fixed jaws placed to protect the heart and lung.  When utilizing VMAT with traditional C arm linear accelerators in breast patients, it can be very difficult to meet the low dose sparring requirements as static collimator rotations are selected per arc which can cause the jaws to be larger than ideal as the gantry rotates around the patient.  There are some more elaborate multiple smaller partial arc techniques which can be used to address this problem, but those techniques aren’t required with this system.  Due to the dual stage stacked and staggered MLC design multiple collimator rotations can be selected and the arcs can be utilized to cover the entire treatment area without the problem of excess low dose to the patient’s heart and lungs from interleaf leakage due to the “per leaf jaw-tracking” effect of this MLC design.  Less out of field dose is another advantage to using a FFF energy which also helps in meeting the very strict low dose OAR requirements of the RTOG 1005 protocol.

Links

Review 3rd party software generated full treatment plan report

PDF

                              

Download full DICOM CT, struct, plan and dose file         

ZIP        

Any reference to a "plan study" are simply what the organizers call each case and may not be a "study" in the FDA sense as they may not have been published in a peer reviewed journal.
Varian does not provide medical advice and these are illustrative examples only.
Leading plans by expert planner. Your results may vary.

FOR EDUCATIONAL AND SCIENTIFIC EXCHANGE ONLY – NOT FOR SALES OR PROMOTIONAL USE.

 

  • Follow Us

Production of any of the material contained herein in any format or media without the express written permission of Varian Medical Systems is prohibited.

Varian Logo