Complexity Comes in 3s - AAMD Publications

6/19/2020

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Complexity Comes in 3sIMPT vs. VMAT Approach in Three-lesion Small Cell Carcinoma

David Alicia, CMDMedical Dosimetrist

Maryland Proton Treatment CenterAffiliated with University of Maryland Medical Center

Disclosure

• There are no disclosures to report

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Maryland Proton Treatment Center

Learner’s Objectives

• To understand the background of the case diagnosis and pulmonary function.

• To gain familiarity with basic proton planning related terms and concepts.

• To comprehend the distinction between treatment planning techniques in IMPT and VMAT.

• To recognize the significant OAR sparing accomplished in the IMPT plan.

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Background of a Case Diagnosis and Pulmonary Function

• 73 Y.O. Male Patient who was a former smoker and drinker with lung problems and shortness of breath.• Dry Cough

• Fluid Coughs ranging from sputum, phlegm, and blood

• Multiple procedures and adjuvant chemotherapy in 2014

• Poor respiratory function

• Supplemental Oxygen


• In Early 2014, diagnosed with invasive moderately differentiated squamous cell carcinoma. • 5.0 cm mass in Left Upper Lobe via Endobronchial Biopsy.

• 3 lymph nodes tested negative for metastatic disease via core needle biopsy.

• 4R (Right Lower Paratracheal node)

• 4L (Left Lower Paratracheal node) (tested twice)

• 7 (Subcarinal mediastinal node)

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• In Mid 2014, patient received a left lung pneumonectomy.

• Upper and lower left lobes of the lung indicated severe emphysema with honeycomb appearance.

• Emphysema is a type of COPD that causes shortness of breath through damage of the air sacs of your lungs.

• Causes:

Cigarette smoke (main cause in the U.S)

Air pollution

Chemical fumes or dusts

• A left posterolateral thoracotomy was also performed. (surgical incision of lung, heart, and esophagus etc. through intercostal spaces).

• To reach access to the central lesion of left upper lobe.


• In 2019, patient was presented with a new mass measuring 3.8 cm in the Right lower lobe in the Right lung.

• Exams have indicated that the mass was a poorly differentiated carcinoma that turned out to be small cell carcinoma.

• Immunostaining tests were performed to make this determination.

• After evaluation of MRI Brain to determine if there were any metastatic disease and PET scans, it was shown that patient has three small cell carcinoma lesions.

• One lesion in the right lower lobe (Primary Tumor)

• One Ispi-lateral Mediastinal Lesion

• One Contralateral Mediastinal Lesion

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Treatment Planning Metrics (Goals and Metrics)

• Total Dose: 150cGy*30 FX:4500cGy• BID (treated twice a day with 6+ hour

separation)

• CBCT/ KV imaging• CBCT First three fractions then weekly

• KV imaging daily

• Weekly QA scans to monitor Tumor response

Treatment Planning Metrics (Goals and Metrics)

The Challenge!!

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CT Simulation Setup

• Patient position: Head First Supine• Chin hyperextended

• Setup Devices:• Wing-board

• Arms up

• Vac-lock

• Compression Belt

• Trolley

Proton Treatment Planning Terms

• Pencil Beam Scanning• Most advanced treatment modality of proton therapy

• IMPT (Intensity Modulated Proton Therapy)• Analogous to IMRT

• Also known as Pencil Beam Proton Therapy

• SFO (Single Field Optimization)• Beams treating target “independently”

• More “robust” than MFO

• Uniform Beam Dose

• MFO (MultiField Optimization)• Beams working together to treat target

• Better OAR sparing

• Non-Uniform Beam Dose

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Proton Treatment Planning Terms

• Range Shifter• External piece of stopping material used

to reduce the treatment range of proton beam. Used for treating shallow/ superficial tumors.

• 2 cm RS, 3 cm RS, 5 cm RS

• Robustness• Planning Metric used in proton therapy

to account for not only setup uncertainty but also range uncertainty due to CT Calibration Curve Error.

IMPT Plan for Case Study

• Two plans with separate isocenters• 1) 2 Field SFO proton plan for

Mediastinal Node (Superior ISO) 15 Degree Superior Angle

180.1 Degree Superior Angle

• 2) 4 Field MFO proton plan for Hilar node and Primary Tumor (Right Lower Lobe) (Inferior ISO) 150 Degree Inferior Angle

180.1 Degree Inferior Angle

200 Degree Inferior Angle

290 Degree Inferior Angle

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IMPT Plan for Case Study (SFO Component)

• 2 Field SFO proton plan for Mediastinal Node (Superior ISO)

• 15 Degree Superior Angle and 180.1 Degree Superior Angle

• Uniform Beam dose

• 3 cm Range Shifter

IMPT Plan for Case Study (SFO-Component)

• 15 Degree Superior Beam• Delivers 50% of the dose (2250

cGy)

• 180.1 Degree Superior Beam• Delivers 50% of the dose (2250

cGy)

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IMPT Plan for Case Study (SFO-Component)

• Planning Objectives for the SFO Plan

*All Beams objectives are SFO related

IMPT Plan for Case Study (MFO Component)

• 4 Field MFO proton plan for Hilar node and Primary Tumor (Right Lower Lobe) (Inferior ISO)• 3 posterior Beams (150 INF,

180.1 INF, &200 INF) to treat Hilar Node

• 3 posterior Beams + 1 Lateral Beam (150 INF, 180.1 INF, 200 INF, &290 INF) to treat the primary tumor

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• 4 Field MFO proton plan for Hilar node and Primary Tumor (Right Lower Lobe) (Inferior ISO• 3 posterior Beams (150 INF,

180.1 INF, &200 INF) to treat Hilar Node

• 3 posterior Beams + 1 Lateral Beam (150 INF, 180.1 INF, 200 INF, & 290 INF) to treat the primary tumor


• Planning Objectives for the MFO plan

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• Planning Strategies:• Max EUD (Raystation Objective)

• Works like a charm

• A-value ranges from 0(mean dose:1) to 150 (max dose)

• Robust Optimization (RaystationObjective)

• Manipulate Snout Position due to the use of Range Shifter

• Be Mindful of clearance issues

• Spot Spacing

• Air Gap 12 cm


• Robustness Parameters:• 0.3 cm setup uncertainty to

preserve the lung and to achieve a steep dose fall

• Range Uncertainty 5%

• Atypical from our standard (0.5 cm setup, 5% range)

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IMPT Plan for Case Study (Dose Volume Histogram)

VMAT Plan Comparison for Case Study

• 2 Full Arcs• 179-181 Counterclockwise Arc

• Collimator 15 degrees

• 181-179 Clockwise Arc• Collimator 345 degrees

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• Overall Dose Distribution


• Clinical Goals

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IMPT vs. VMAT Dose Distribution

• Overall Dose Distribution

IMPT vs. VMAT Dose Volume Histogram

• Show DVH

**Dotted Lines: IMPT Solid Lines: VMAT**

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Special Acknowledgement

Dr. Pranshu MohindraRadiation Oncologist

Dr. Robert MillerRadiation Oncologist

• MPTC/UMMC Physics and Dosimetry Team

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Documents

Complexity Comes in 3s - AAMD Publications