Dosimetriccomparisonof brachyterapy techniquesforAPBI...2014/10/03 · Clinical studies reporting dose-volume parameters of high-dose-rate interstitial breast brachytherapy CT image-guided

Dosimetric comparison of brachyterapy

techniques for APBI

Tibor MajorNational Institute of Oncology, BudapestNational Institute of Oncology, Budapest

Euro-Asian Breast Brachytherapy School, October 9-10. 2014, Erlangen

Outline

• classification of BT irradiation techniques for APBI

• dosimetry and optimization in multicatheter interstitial BT

• single lumen balloon and multilumen applicators

• intraoperative electronic brachytherapy with X-ray

• beyond the TG-43 brachytherapy dose calculation formalism

APBI

brachytherapy

endocavitary

interstitial electronic

endocavitary

MammoSite Contura SAVI ClearPath

HDR seedIntrabeam Axxent

Dose dependence on distance in brachytherapy

0,8

1

1,2

1,4

Rel

ativ

e do

se

Ir-192

Ra-226

Correction for absorption and scattering in water

2x1

D ≈

0

0,2

0,4

0,6

0 1 2 3 4 5 6 7 8 9 10 11

Rel

ativ

e do

se

Distance (cm)

I-125Pd-103

inverse square law inhomogeneous dose distribution

Dose homogeneity in brachytherapy

Dose non-uniformity ratio (DNR)

Dose homogeneity index (DHI) for implant

100

150

VV

DNR =

DNRV

VVDHI

100

150100 −=−= 1

Dose homogeneity index (DHI) for target

V100V150V100

DHI−=

V100 = volume receiving equal to or greater than the prescribed dose

V150 = volume receiving equal to or greater than 1.5 x the prescribed dose

V100 = percentage volume of the target receiving equal to or greater than the prescribed dose

V150 = percentage volume of the target receiving equal to or greater than 1.5 x prescribed dose

For homogeneous dose distribution the DNR is low and DHI is high

Definition of dose non-uniformity ratio (DNR)

Vref V1.5xref

V1.5xrefDNR =

Vref

DNR is specific to the implant geometry and prescription isodose

The dose distribution is optimal when the DNR is minimal

Vref = volume receiving equal to orgreater than the reference dose

V1.5xref = volume receiving equal to or greaterthan 1.5 x the reference dose

PTV

ref

VPTV

CI =

Definition of coverage index (CI) and conformal index (COIN)

ref

ref

PTV

ref

VPTV

VPTV

COIN ⋅=

Both indices (CI, COIN) have to be maximized during opti mization

1. No optimization (Paris Dosimetry System)• uniform dwell times

2. Forward optimization• manual optimization (editing dwell times/weights)• geometrical optimization (on distance and volume)• polynomial optimization on

Optimization methods in HDR BT

• polynomial optimization on- distance dose points (dwell time gradient restrictions)- volume dose points (SSDS – extension of PDS)- dose points on the target surface (conformal)

• graphical optimization (only for local adjusments)

3. Inverse optimization (IPSA)• anatomy based with surface and volume dose objectives

Manual optimization

changing dwell times individually

Geometrical optimization

- no dose points are needed (only for normalization) - the dwell time at a dwell position is inversely proportional to the dosedelivered by other dwell positions

- the dose at the dwell position given by another dwell position isinversely proportional to the square of its distance to that dwell position

Graphical optimization

Distance dose points50 %

100 %150 %

Paris50 %

100 %150 %

Dose distributions at different optimizations for radiogra phy-based implants

GO50 %

100 %150 %

Conformal50 %

100 %150 %

CI DNR COIN

Distance dose points 0.70 0.35 0.40

Paris system 0.61 0.25 0.34

Average values of volumetric indices for 17 patients

GO 0.66 0.25 0.50

Conformal 0.92 0.55 0.74

Since no optimization method can compensate for the inadeq uate implant

geometry, preimplant 3D anatomical information is requ ired for planning the

catheter positions in order to obtain optimal dose distribu tion.

Major et al. Strahlenther Onkol 181:89-96. 2005

Preimplant CT for defining the catheter positions

3D anatomical and catheter reconstruction

Conformal dose distribution after geometrical and graphi cal optimization

GO vs. GO + GRO(25 patients)

GO GO + GRO p

CI 0.87 0.91 0.0003

DNR 0.30 0.33 0.0098DNR 0.30 0.33 0.0098

COIN 0.64 0.67 < 0.0001

GO: geometrical optimizationGRO: graphical optimization

The graphical optimization improved the quality of dose distributions

GO + GRO

Conformal

GO + GRO vs. CONF

Conformal

GO + GRO vs. CONF(28 patients)

GO + GRO CONF p

CI 0.91 0.88 0.0013

DNR 0.33 0.54 < 0.0001

COIN 0.68 0.77 < 0.0001COIN 0.68 0.77 < 0.0001

Vref (ccm) 75.3 64.3 < 0.0001

GO: geometrical optimizationGRO: graphical optimizationCONF: conformal (dose point optimization)

Major et al. Radiother Oncol 90:48-55. 2009

The conformal dose point optimization provided highly conformal plans,but at the cost of unacceptable high dose inhomogeneity

Interstitial breast brachytherapy study

Interstitial brachytherapy alone vs. external beam radia tion therapy after breastconserving surgery for low risk invasive carcinoma and low risk duct carcinomain-situ (DCIS) of the female breast

Phase III Multicenter Trial - European Brachytherapy Breast Cancer GEC-ESTRO Working Group

DVH analysis for plan evaluation

Conventional planning

• Vref, V1.5xref, V1.5xMCD• DNR ( 0.90)• DHI• COIN

Average plan parameters for 49 patients(GEC-ESTRO Phase III. trial)

Major et al. Brachytherapy 10:421-426. 2011

Author n V90 V100 D90 DHI

Fluoroscopy guided + postimplant CT Vicini (1999)Kestin (2000)Cuttino (2005)Weed (2005)Major* (2005)

811151017

NRNR

89%68%76%

68%68%

96% †

58%70%

69%NRNRNR

72%

0.890.830.77NR0.65

Clinical studies reporting dose-volume parametersof high-dose-rate interstitial breast brachytherapy

CT image-guided (pre-, postimplant CT)Kolotas (1999)Das (2004)Cuttino (2005)Aristei (2007)Major** (2011)

4250144649

NRNR

95%NR

96%

90%95%

98% †

NR92%

NRNRNR

96%102%

NR0.730.820.760.65

*Major et al.: Strahlenther Onkol 181:89-96. 2005**Major et al. Brachytherapy 10:421-426. 2011

n = number of patients, NR = not reported, * for PTV 2 cm, † for PTV 1 cm, ‡ dose homogeneity index for the implant

Permanent breast seed implant technique

Dpresc = 90 GyMean no. of. Pd-103 seeds: 75Mean no. of needles: 17Mean total activity: 181.8 UPreimplant V100 = 97%Postimplant V100 = 88%

Pignol et al. IJROBP 64:176-81.2006Keller et al. IJROBP 83:84-92.2012

0,6

0,8

1,0

1,2

1,4

Re

alt

ive

do

se

Radial dose funtions for different isotopes

Ir-192

0,0

0,2

0,4

0,6

0 1 2 3 4 5 6 7 8 9 10

Re

alt

ive

do

se

Distance (cm)

I-125Pd-103

Permanent breast seed implant with Pd-103 or I-125 ?

Emean= 21 keVT1/2= 17 days

Emean= 27.4 keVT1/2= 59 days

The 1% isodose line is just below the skin for the Pd-103, whereas the 5% isodose line is about at the same position for the I-125 case. The Pd-103 implant is associated with a rapid dose fa ll-off.

Less than 5 mSv dose to the patient’s partner with Pd-103 seeds

Keller et al. IJROBP 62:358-365. 2005




• intraoperative electronic brachytherapy with X-ray• intraoperative electronic brachytherapy with X-ray


Intracavitary BT applicators

MammoSite balloon catheter

- single and multilumen (central + 3 lumens)

Contura Multiple Lumen Balloon Catheter

- central + 4 lumens

ClearPath Brachytherapy System

- 6 tubes

SAVI (Strut-Adjusted Volume Implant)

- 6-10 struts

MammoSite breast balloon applicator

single lumen for the Ir-192source

PTV generation with volume expansion

PTV csak emlıszövetet tartalmazPTV includes breast tissue only

Dose distribution around MammoSite applicator

ref. point

Dose prescription point is at 1cm from balloon surface

point source linear source

compensation for the anisotropy of the Ir-192 source

Dose homogeneity vs. balloon diameter

Dmax at the balloon surface is in the range of 175 – 250% of the prescribed dose

Volume parameters for interstitial and MammoSite BT

IBCONV - conventional interstitial brachytherapyIBCONF - conformal interstitial brachytherapyMSB - MammoSite brachytherapy


Quality indices for interstitial and MammoSite BT



Dose parameters for interstitial and MammoSite BT



Skin and chest wall dose with multi-catheter (MC) a nd MammoSite(MS) breast brachytherapy: Implications for late toxi city

The dosimetric data for 43 patients treated with the MC technique and 83 patients treated with the MS at Virginia Commonwealth University were reviewed.

Cuttino et al. Brachytherapy 8:223-226. 2009

The MC technique results in more conformal dose delivery, with significantly lower mean skin and chest wall doses.

Single and multiple dwell position methods in MammoSite

single dwell position multiple dwell positions

Kim et al. JACMP 11:54-63. 2010data from plans of 19 patients

Drawbacks of MammoSite applicator

- circular dose distribution in perpendicular plane to balloon axis

- balloon asymmetry leads to asymmetric PTV coverage

- the dose to OARs is determined by their position relative to the applicator

- the only option to reduce dose to the organs at risk (OARs) is by reducing

the prescription dose and hence the target dose

multilumen applicator

Optimization and comparison of balloon-based partia l breast brachytherapyusing a single source, a standard plan line source, and both forward and

inverse planned multilumen (ML) techniques(12 patients, virtual ML plans)

single source line source

forward ML inverse ML

- multiple sources in a single catheter improve coverage at catheter ends, whereas ML can further improve coverage and reduce dose to organs at risk.

- patients previously ineligible for treatment with a single catheter may be treated using ML applicator.

Eyre et al. Brachytherapy 12:107-113. 2013

Other multilumen breast applicators

Contura multi-lumen balloon (MLB) ClearPath applicator SAVI applicator

- avoidance of high dose in the skin - reduction of the size of an air/fluid pocket in the planning target volume through the use of vacuum ports

Advantages of Contura multilumen balloon catheter over MammoSite

Contura multi-lumen balloon (MLB) applicator

5 mm

Central lumen + four catheters

Contura catheter has a sixth lumen (vacuum ports)through which air/fluid can be removed

before suctioning air after suctioning air7.7 % of PTVEVAL 0.4 % of PTVEVAL

Suctioning air/fluid improves tissue-balloon conformance, thereby allowing a higherdose of radiation to be delivered to the breast tissue at greatest risk of tumor cells.

Contura vs. MammoSite catheter regarding the applicabil ity for APBI

Two treatment planning goals:- maximum skin dose

Dosimetrical comparison between multilumen MammoSiteand Contura Multilumen Balloon applicators

(median values in % of prescribed dose)

V95 V150 V200 Skinmax Ribmax

ML MammoSite (8 pts.) 98.0 31.6 7.4 92.5 92.7

Contura (12 pts.) 97.6 28.2 7.5 98.2 104.0Contura (12 pts.) 97.6 28.2 7.5 98.2 104.0

Both applicators have shown the ability of dose shaping for providing

sufficient target coverage while concurrently limiting dose to skin and rib

Fu et al. University of Pittsburgh Cancer Institute, Pittsburgh, PA

Improvements of dose distributions with inverse planning (IPSA)

- 4 treatment plans for 24 patients- 2 optimization methods (IPSA, dose points)- 2 types of applicators (Contura multilumen, simulated single lumen)

Skowronek et al. J Contemp Brachytherapy 5:134-38. 2013

- dose distribution obtained using multi-lumen IPSA optimized application was characterized with the highest target coverage while preserving acceptable doses to organs at risk

- optimization method was proven to be more important than the number of catheters in the applicator, however, overall outcome of multi-lumen application gives more possibilities of dose distribution adjustment

ClearPath breast applicator

6 catheters

Multicatheter hybrid breast brachytherapy: A potenti al alternative for patients with inadequate skin distance

- 11 patients not treated with MammoSite due to inadequate skin distance- simulated plans with ClearPath catheter

Beriwal et al. Brachytherapy 7:301-304. 2008

The hybrid CP catheter reduced the skin dose significantly without compromising the planning target volume coverage, DHI, or dose to other critical organs.

MammoSite ClearPath p

PTV coverage

V90% 99.6 99.7 ns.

V100% 96.5 96.5 ns.

High dose region

V150% 42.1 42.9 ns.

V200% 11.4 15.2 < 0.05

A dosimetric comparison of MammoSite and ClearPath bra chytherapy devices(mean values for 15 patients)

V200% 11.4 15.2 < 0.05

OAR

Ipsilateral breast (V50%) 19.8 18.0 < 0.05

Ipsilateral lung (V30%) 3.7 2.8 < 0.05

Heart (V5%) 57.0 54.3 < 0.05

Maximal skin dose (%) 92 80 < 0.05

Dickler et al. Brachytherapy 8:14-18. 2009

The MammoSite and ClearPath methods of PBI offer comp arable target volume coverage,

however the ClearPath device achieves increased OAR sparing.

Strut-Adjusted Volume Implant (SAVI) applicator(central + 6-8-10 peripheral struts)

Clinical implementation of SAVI

- the dose distribution can conform to the modified PT V (PTVEVAL)- less skin dose- patients not eligible for MammoSite can be treated with SA VI

Scanderberg et al. Radiother Oncol 90:36-42. 2009

Clinical experience with the SAVI brachytherapy appli cator

SAVI applicator with very close skin margin skin dose is kept low

Yashar et al. Brachytherapy 8:367-372. 2009

Almost half of evaluated patients were not candidates for other single-entry

brachytherapy devices because of skin spacing or brea st size, demonstrating an

expansion of candidates for single-entry partial br east brachytherapy

- 9 patients treated with SAVI- plans for MammoSite and 3D-CRT

Evaluation of three APBI techniques under NSABP B-3 9 guidelines

preimplant 3D-CRTSAVI

Scanderberg et al. J Appl Clin Med Phys 11:274-280. 2010

The maximum rib, lung and skin doses were lowest for the SAVI

Nonivasive image-guided breast brachytherapy (AccuBoost system)

Hepel et al. Brachytherapy 2014

- the breast is positioned between the compression plates and immobilized with gentle compression- a kV image is obtained where the tumor bed is identified- appropriately sized and shaped applicators are selected to target, the position is determined by the localization grid- the applicators are attached to an Ir-192 HDR afterloader for treatment delivery- the process is then repeated in an orthogonal axis.

Composite dosimetry using a fixed model

Dosimetric characterization of AccuBoost system

applicators

Geometry for MC calculations

Experimental setup for measurements

30 mm depth 0 mm depthClinical application

Rivard et al. Med Phys 36:5027-32. 2009

Geometry for MC calculations 30 mm depth 0 mm depth

Isodose distribution for parallel-opposed„beams” using two applicators with Θ6 cm

Dose profiles on film and with MC Dose distributionson radiochromic film

Clinical application


• dosimetry of and optimization in multicatheter interstitial BT




Intrabeam X-ray (Carl Zeiss Meditec AG)(max. 50 kV)

X-ray source

Floor stand Spherical aplicatorswith diameters of

1.5 – 5.0 cm

spherical dosedistribution

TARGIT-A study (TARGeted Intraoperative radioTherapy) 5-year results in Lancet 2013

Intrabeam clinical application – single treatment for appr ox. 30 minutes

20 Gy at the surface5-7 Gy at 1 cm depth

high hose gradient

large dose inhomogeneity

Radial dose functions for isotopes and photon energies use d in BT

Rivard et al. Med Phys 33:4020-32, 2006

Axxent TM eBx system (Xoft Inc., CA, USA)(40 – 50 kV X-ray)

- similar dose distribution to LDR I-125- similar dose rate to HDR Ir-192 (0.6 Gy/min)- can be switched off

radiation source in a balloon applicator

Contura multilumen balloon BT vs. 50 kV X-ray IORT

- 14 patients treated with Contura- replanning for 50 kV X-ray system with TG-43 data for Xoft system

50 kV X-ray Contura20 Gy15 Gy10 Gy

20 Gy15 Gy10 Gy

Jones et al. Brachytherapy http://dx.doi.org/10.1016/j.brachy.2014.04.005

A representative comparison of dose distributions

The HDR brachytherapy plans were superior to 50 kV superficial photon plans forIORT in all dosimetric parameters except for the heart and rib dosimetric parameters

Jones et al. Brachytherapy http://dx.doi.org/10.1016/j.brachy.2014.04.005


• dosimetry of and optimization in multicatheter interstitial BT


• intraoperative electronic brachytherapy with X-ray• intraoperative electronic brachytherapy with X-ray


),()(),(

),(),( Θ⋅⋅

ΘΘ⋅Λ⋅=Θ

•rFrg

rG

rGSrD k

00

Med. Phys. 22:209-234. 1995.

Sk = air-kerma strengthΛ = dose rate constantG(r,Θ) = geometrical functiong(r) = radial dose functionF(r,Θ) = anizotropy function

- no inhomogeneity correction (CT/MRI/UH only in the backg round for

catheter/applicator reconstruction)

- assumption of full scattering condition (infinite mediu m)

- no correction for source movement of HDR source (only dwe ll times)

- no correction for applicator/catheter absorption

- no correction for seed absorption

Limitations of TG-43 formalism

Model-based dose calculation algorithms (MBDCAs) either explicitly simulate thetransport of radiation in the actual media or employ multiple dimensional scatter integration techniques to account for the dependence of scatter dose on the 3D geometry.

Beaulieu et al. Med Phys 39.6208-36. 2012

Dosimetrical comparison between TG43 and MBDCA for APBI patients

Differences between dose calulations using TG-43 and TG-186 formalisms

Preliminary results based on 38 APBI patients data

On average, percentage differences between MBDCA and TG43-based dosimetric indices are:- < 1% for the PTV and 1-1.5% for dose homogeneity and conformity indices- 6% for skin (D0.1cc) -10% for the lung (V10Gy) - with a strong correlation of the observed differences to the target location

Bilateral research cooperation between Medical Physics Laboratory, Medical School, University of Athensand National Institute of Oncology, Radiotherapy Department, Budapest

Documents

Dosimetriccomparisonof brachyterapy techniquesforAPBI...2014/10/03 · Clinical studies reporting dose-volume parameters of high-dose-rate interstitial breast brachytherapy CT image-guided