Treatment Planning Techniques for Larger Body Habitus Patients for Breast/Chestwall and Regional Lymph Nodal Irradiation By Ruth Ann M. Good, CMD. R.T. (R)(T) Virginia Commonwealth University, Richmond, VA
Adult Body Mass Index (BMI) BMI = Weight in Kilograms/Height in meters squared All Cases Obese/Extreme Obese Range The weight range 225lbs-363lbs https://www.cdc.gov/obesity/adult/defining.html
https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet
Four Different Treatment Techniques 1) Single Isocenter with Extended Tangent Fields 3D 4 Fields 2) Photon/Electron Mix Total Nodal Left Breast 3D 5 Fields 2a) Photon/Electron with Split Mixed Energy IMC 3D 6 Fields 3) Arc Treatment Planning VMAT 2- Split Arcs (4 Fields Total) 4) Prone Total Nodal Single Isocenter 3D 4 - Fields
SIMULATION/IMMOBILIZATION Patient Position: Supine, flat on a wing board Custom vac-bag with both arms up Head turned to contralateral side
Patient Alignment Visually align patient confirm with CT Leg roll under knees
ALIGNMENT TATTOOS Three Anterior Tattoos + Two Lateral Tattoos Done in free breathing
CT Assessed for Active Breathing Control (ABC- Deep Inhale Breath Hold) Physics staff works with the patient to learn ABC Breath Hold technique Three ABC scans are done to check reproducibility Final Free Breathing scan for isocenter placement.
ABC Lung Comparison Free Breathing 1077cc s of Ipsi Lung Active Breathing Control 46.7% increase in lung volume 1580cc s of Ipsi Lung
All contours follow the RTOG Breast Cancer Atlas Dose constraints from NSABP Protocol B51/RTOG 1304 50Gy/25fractions https://www.rtog.org/corelab/contouringatlases/breastcanceratlas.aspx
Single Isocenter with Extended Tangent Fields 4 Field Technique 3D
Isocenter Placement Isocenter is placed ~1-2cm from lateral chestwall Table vertical may be dictated by clearance
Sclav/Axilla fields - gantry angle off cord PRV and Esophagus Tangent fields - gantry angle off contralateral breast, minimal lung and cover IMNs RAO Sclav/Axilla Field RAO Lt Medial Chestwall Tangent
Tangent fields 6x/18x (Separations larger then ~23cm) LPO Sclav/Axilla Gantry angle matches divergence of medial edge of RAO Sclav
Optimized Sclav/Axilla Tx Plan Optimized Tangent Chestwall Tx Plan 93% Isodose line (green line) normalized to max point 92% Isodose line (green line) normalized to max point
Final Composite Plan 4 Field Technique
Final DVH for Extended Tangents/Single Isocenter
VCU s Excel Spreadsheet for Total Nodal Irradiation following Protocol B-51/RTOG 1304 dosing constraints
Photon/Electron Mix Total Nodal Left Breast 5 Field Technique / 3-D Treatment Plan
Decision to do ABC breath hold technique on Left Breast / Total Nodal Irradiation Free Breathing Scan ABC Breath Hold Scan
Free Breathing ABC Breath Hold with ABC heart contour Sagittal heart contour
Total of 8 Treatment Fields for Photon/Electron Technique Dual Energy 6x/18x Tangent Photon Fields Dual Energy 6x/18x RAO Lt Sclav Electron field at 105SSD to clear Chest and Abdomen
Single Isocenter for Tangent Breast fields and Sclav/Axilla fields 2mm Overlap of IMN field into Medial Lt Breast Tangent field The tangent gantry angle between 20-45 degrees. Minimize the lung included in the tangent field Gantry angle of IMC is ~ 5-10 degrees less then Medial tangent field.
Energy selection for Electron IMC field 4.8cm depth 16e calculated to Dmax
A contour is created with a 3mm circle on each transverse slice on the Medial edge of the Medial Tangent field. This contour assists in block design of the IMC and Lateral Breast fields.
Medial Border Contour used for block design Match for Lateral Tangent and 2mm overlap of IMC field Superior border of IMC field is inferior border of Supraclavicular field 2mm overlap of IMC field into Medial Tangent field entire field length
Optimized Left Breast Tangents and Left Sclav/Axilla Tx Plans Lt Breast plan 94% (green line) of Max dose Lt Sclav/Axilla plan 95% (red line) of Max dose
Combined composite plans Top plan is all plans combined without any additional field in fields to cool off hot spots Lower plan is adding additional field in fields on Medial 18x to cool off hot spots
Control Points (Field in Fields) for Medial Lt Tangents 18x field Control points 2-4 only are the field in fields that cool off the hot spot by ~6Gy Sclav field similar set of control points at the inferior border of field
Final Composite Plan for Photon/Electron Mix for Left Breast and Total Nodal Irradiation 8 total fields / 3-D treatment plan
DVH Photon/Electron Mix Lt Breast and Total Nodal Irradiation
Dose Summary for Photon/Electron Mix Left Breast with Total Nodal Irradiation
1 st Day KV OBI at single isocenter plus the total time line including all portals with double exposure 16min 20secs
1 st day MV portals of Lt Sclav and Medial Lt Breast Tangent
Photon/Electron with Split Mixed Energy IMC Upper electron field 16e and lower 12e to reduce heart dose to <5Gy Mean Two matchline changes of 1cm each after the 8 th and 16 th fraction new blocks
3D view of matchline changes and sagittal view - 1cm block change on skin
Heart Mean dose of 4.12Gy
When 3-D treatment plans are not in acceptable dose ranges for MDs : Arc Treatment Planning Upper treatment plan of mixed Photon/Electron with ipsilateral lung dose too high Lower treatment plan 4 Arcs with lower ipsilateral lung dose at 20Gy
Comparison of Photon/Electron Mix Vs. Arc Treatment Plan DVHs Photon/Electron Mix plan higher ipsilateral lung doses but lower heart dose(dash lines)
Right Breast with Total Nodal Irradiation ARCs 4 field/ VMAT
Four Arc Fields Two Split fields for each CW and CCW on gantry - Overlap of 2cms Gantry Angle for CW is 210-45 with a collimator of 5 Gantry Angle for CCW is 47-212 with a collimator of 355
Arc Treatment Plan DVH
Arc Treatment Plan Dose Summary for 50Gy/25fractions
Prone Total Nodal 4 Field Technique
Prone Simulation/Immobization Prone board with custom insert with larger opening, custom 1cm bolus on inferior board Vac-bag abutting arm pegs with rectangular sponge to fill opening in our board 2 inch Styrofoam placed under breast to lift off table and to index breast location
Simulation Positioning Tape Ipsilateral arm out of way if needed Pull Contralateral breast as far away as possible from Ipsilateral breast Leg roll under ankles and belly pulled as flat as possible inferiorly
Tattoo Locations Three Posterior tattoos Right and Left lateral tattoos- matches index location
Left Breast Prone
Lt Breast Prone Fields Isocenter placed below Sclav PTV and above IMN PTV Mixed 6x/18x Sclav/Axilla field must also fully cover Breast PTV
Lateral Tangent Field in Field
Sclav Field in Field Blocking to cool off junction
DVH for Left Prone Total Nodal/Single Isocenter
Prone Left Breast Total Nodal Irradiation Not covering inferior IMNodes-Heart dose priority
Additional Setup Distances Table Vertical Board to Breast at Tattoos
1 st Day Portal Images Left Prone Breast
Setup KV OBI
Right Breast Prone/Supine Comparison
Right Prone Breast Total Nodal
Dose Constraints Met for Right Prone Breast
Conclusions 1) Single Isocenter with Extended Tangent Fields Most simplistic 3D Total Nodal Plan Must clear contralateral breast yet cover IMN PTV If >23cm separation add higher photon energy Tangent field must be 20cm or less in length Make sure ipsi-lung dose and heart dose are low enough ABC can be utilized to minimize lung and heart dose 2) Photon/Electron Mix Total Nodal Used when contralateral breast in extended tangent field Too much lung in Extended Tangents - ~4cm or greater Less then ~ 5cm thick at location of IM Nodes to be able to use 16 electrons or less Electron IM Field needs to be >3.5cm in width
Conclusions 3) Arc Treatment Planning Used when 3D plans do not meet dose constraints per protocol May have to split Arcs from left to right due to patients width and length ABC is not utilized currently with Breast Arc planning May need to add additional regions of interest Esophagus, Stomach, Liver, and Airway. 4) Prone Total Nodal Used on very pendulous breasts Very important to make sure the patient is able to be comfortable enough to be on the table for >30 minutes
How we all feel by Friday Questions/Answers