ARRO ContourAccelerated Partial Breast Irradiation

using HDR brachytherapy or EBRT

Michael Zhang (MSIV), Matthew Spraker, MD, PhD (PGY3)

Faculty Mentor: Janice Kim, MD

University of Washington / Seattle Cancer Care Alliance

Seattle, WA

November 16, 2015

CT Simulation and Prescription for Brachytherapy

• CT simulation

– Use at least 1.5mm slices to visualize catheters for dosimetry planning*.

– Scan from chin to bottom of diaphragms, including the entire ipsilateral breast and lung.

– Breath hold CT scan can be performed

• Dose is delivered as 3.4Gy BID x 5 days (34Gy total)

• 34 Gy prescribed to approximate 1cm radial distance from the device surface.

November 16, 2015

*We use 1.25mm slices at our institution

Simulation and Planning for Brachytherapy

• Targets and OARs

– CTV volume – device balloon/seroma cavity and clips if present.

– PTV eval – CTV volume plus 1cm radial expansion

– External Skin Surface contour– 3mm thickness for extent of balloon

– Trapped Air bubbles

– Whole breast

– Lungs, Ribs and Heart for left-sided lesions.

November 16, 2015

Targets and OARs for Brachytherapy

November 16, 2015

PTV Eval

Air bubble

CTV

Catheters

Rib

Skin surface

November 16, 2015

Targets and OARs for Brachytherapy

Simulation and Planning for EBRT

• CT scan from base of skull to bottom of diaphragms to ensure inclusion of entire lung, heart and breast

• Slice thickness of <5mm should be employed

• Field within field planning technique can be used to improve dosimetry, but IMRT planning was excluded from NSABP B39/RTOG 0413 protocol.

• Dose calculations with tissue inhomogeneity correction were required in the NSABP B39/RTOG 0413 protocol.

• Note treatment delivered in 3.85Gy BID x10 for total dose of 38.5Gy.

November 16, 2015

Simulation and Planning for EBRT

• Targets and OARs

– CTV – uniformly expand resection cavity 15mm

– PTV – uniformly expand CTV 10mm

– PTV_eval – excludes PTV within 5mm of skin or chest wall

– Skin

– Ipsilateral and contralateral breast

– Thyroid

– Ipsilateral and contralateral lungs

– Heart

November 16, 2015

Targets and OARs for EBRT

November 16, 2015

CTV

PTV_eval

Skin

Left lung

Right lung

Heart

Targets and OARs for EBRT

November 16, 2015

CTV

PTV_eval

Skin

Left lung

Right lung

Heart

Targets and OARs for EBRT

November 16, 2015

CTV

PTV_eval

Skin

Left lung

Right lung

Heart

Isodose lines for EBRT

November 16, 2015

Isodose lines for EBRT

November 16, 2015

Isodose lines for EBRT

November 16, 2015

APBI dose constraints (NSABP B39/RTOG 0413 )

Target or OAR Constraint

Target coverage PTV_Eval V90≥90%

Whole breast V150<50cc, V200<10cc, V50<60% whole breast

Volume (air+seroma)/PTV_Eval <10%

Skin Max dose<145%

Device to skin bridge distance ≥5mm (ideally ≥7mm)

Balloon/device symmetry Device ≤2mm from expected dimensions

Vol. trapped air limitation ([Vol trapped air/Vol PTV_EVAL] x 100%) ≤ %PTV_EVAL coverage – 90%

November 16, 2015

Single-entry intracavitary device

Vx = Volume receiving x% of prescription dose

APBI dose constraints (NSABP B39/RTOG 0413 )

Target or OAR Constraint

Target coverage PTV_Eval V90≥90%

Dose homogeneity V150≤V100/4

Whole breast V150<70ccV200<20ccV50<60% whole breast

Volume (air+seroma)/PTV_Eval <10%

Skin Max dose<100% prescription

Device to skin bridge distance ≥5mm (ideally ≥7mm)

Ribs Max dose<145% prescription

November 16, 2015

Multiple Independent Catheter Insertion

Vx = Volume receiving x% of prescription dose

APBI dose constraints (NSABP B39/RTOG 0413 )

Target or OAR Constraint

Target coverage PTV_Eval V90≥90%

Dose homogeneity Max dose ≤120% prescription dose

Ipsilateral breast V100<35% whole breastV50<60% whole breast

Contralateral breast Max dose at any point <3% prescribed dose

Ipsilateral lung V30<15% lung

Contralateral lung V5<15% lung

Heart V5<5% (R-sided lesions)V5<40% (L-sided lesions)

Thyroid Max dose at any point <3% prescribed dose

November 16, 2015

External beam radiotherapy