Aperture-based IMRT for GYN malignancies

Aperture-based IMRT for Aperture-based IMRT for GYN malignanciesGYN malignancies

Myriam Bouchard Myriam Bouchard S. Nadeau , I. Germain, P.-É. S. Nadeau , I. Germain, P.-É.

Raymond, F. Harel, F. Beaulieu, L. Raymond, F. Harel, F. Beaulieu, L. Beaulieu, R. Roy, L. GingrasBeaulieu, R. Roy, L. Gingras

Department of radiation oncology of Department of radiation oncology of

L’Hotel-Dieu de Quebec, QC, CanadaL’Hotel-Dieu de Quebec, QC, Canada

Results from the dosimetric study – 2005/2006

ObjectivesObjectives Contours definitionContours definition

– TargetTarget– Organs at riskOrgans at risk

Aperture-based vs Beamlet-based Aperture-based vs Beamlet-based IMRTIMRT

Gains vs Uncertainties in IMRT for Gains vs Uncertainties in IMRT for GYNGYN

Selected casesSelected casesEndometrial / Uterus cervix cancerEndometrial / Uterus cervix cancer

Post-operative EBRTPost-operative EBRT

= = Local Control benefitLocal Control benefit

PORTEC, Creutzberg et al. Lancet (2000) (endometrium)PORTEC, Creutzberg et al. Lancet (2000) (endometrium)GOG-99 (endometrium)GOG-99 (endometrium)Sedlis Sedlis Gyn Oncology (1999) (cervix)Gyn Oncology (1999) (cervix)

Purpose of txPurpose of tx

No survival benefit, attempt to reduce side effects from adjuvant

treatments

What do we treat?What do we treat?

GYN postop EBRTGYN postop EBRT

CTVCTV External iliac nodesExternal iliac nodes Internal iliac nodesInternal iliac nodes Obturator nodesObturator nodes Presacral regionPresacral region 1/2 superior of vagina1/2 superior of vagina ParametersParameters

ControversiesControversies

CTVCTV

Controversies -- CTVControversies -- CTV Endometrium CTV Endometrium CTV ÞÞ Cervix CTV Cervix CTV

– Presacral regionPresacral region

Presacral CTV / 4-fieldPresacral CTV / 4-field

CTV95% Isodose

Controversies -- CTVControversies -- CTV Endometrium CTV Endometrium CTV ÞÞ Cervix CTV Cervix CTV

– Presacral regionPresacral region Upper limit ?Upper limit ?

– L5-S1, L4-L5… (common iliac LN)L5-S1, L4-L5… (common iliac LN) External iliac limitExternal iliac limit

Ant limit / Ext. Iliac LNAnt limit / Ext. Iliac LN

Controversies -- CTVControversies -- CTV Endometrium CTV Endometrium CTV ÞÞ Cervix CTV Cervix CTV

– Presacral regionPresacral region Upper limit ?Upper limit ?

– L5-S1, L4-L5… (common iliac LN)L5-S1, L4-L5… (common iliac LN) External iliac limitExternal iliac limit Margin around vesselsMargin around vessels

– How big?How big?

Pelvic LN mapping Pelvic LN mapping literatureliterature

Taylor Taylor et alet al 20 patients, GYN malignancies20 patients, GYN malignancies

MRI + iron oxyde particlesMRI + iron oxyde particles

CTV = CTV = – margins 3-5-7-10-15 mmmargins 3-5-7-10-15 mm– PTV = CTV + 1 cmPTV = CTV + 1 cm

Taylor Taylor et alet al

CTV CTV MarginsMargins

N coverageN coverage Bowel Bowel inside PTVinside PTV

5 mm5 mm 76%76% ------

7 mm7 mm 88%88% 146,9 cc146,9 cc

10 mm10 mm 94%94% 190 cc190 cc

15 mm15 mm 99%99% 266 cc266 cc

Taylor et al

99% coverage modified-7 mm99% coverage modified-7 mm

18 patients with prostate cancer N+18 patients with prostate cancer N+ Margin 2 cm around vessels (includes PTV)Margin 2 cm around vessels (includes PTV) 94,5 % N coverage94,5 % N coverage

Controversies -- CTVControversies -- CTV Endometrium CTV Endometrium CTV ÞÞ Cervix CTV Cervix CTV

– Presacral regionPresacral region Upper limit ?Upper limit ?

– L5-S1, L4-L5… (common iliac LN)L5-S1, L4-L5… (common iliac LN) External iliac limitExternal iliac limit Margin around vesselsMargin around vessels

– How big?How big? ITV… bladder fillingITV… bladder filling

– MDACC = fusion pre-postmictional MDACC = fusion pre-postmictional CTsimCTsim

ITV 1 cmITV 1 cm

CTV – CTV – ourour initial choices*initial choices*

External iliac nodesExternal iliac nodes Internal iliac nodesInternal iliac nodes Obturator nodesObturator nodes Presacral regionPresacral region 1/2 superior of vagina1/2 superior of vagina ParametersParameters

+ 5 mm around vessels

ITV 1 cm

*Before RTOG 0418, Shih et al. and Taylor et al. publications

3D CTV3D CTV

PTV = CTV + 1 cmPTV = CTV + 1 cm

OARsOARs Bowel (colon + small bowel)Bowel (colon + small bowel)

– Region at risk to find bowelRegion at risk to find bowel

= RAR-B= RAR-B RectumRectum BladderBladder Bone marrowBone marrow

Bowel / RAR-BBowel / RAR-B

Why IMRT for GYN ?Why IMRT for GYN ?

Inadequate coverageInadequate coverage

PTVPTV

Conventional 4-Conventional 4-fieldsfields

95% Isodose

Inadequate coverageInadequate coverage Greer et al. (1990)Greer et al. (1990)

S2-3 post limit : S2-3 post limit : 49% inadequate49% inadequate coverage coverage 87% com. il. bifurcation above L5-S187% com. il. bifurcation above L5-S1

Bonin et al. / Pendelbury et al. Bonin et al. / Pendelbury et al. (1993) (1993)

45% / 62% inadequate coverage45% / 62% inadequate coverage ext. il LN ext. il LN

Finlay et al. (2006)Finlay et al. (2006) 95,4% at least 1 inadequate margin with bony 95,4% at least 1 inadequate margin with bony

landmarkslandmarks

IMRT for GYN IMRT for GYN malignanciesmalignancies

Mundt Mundt et alet al.(Chicago, 2000).(Chicago, 2000)Portelance Portelance et alet al.(St. Louis, 2001).(St. Louis, 2001)Heron Heron et alet al.(Pittsburgh, 2003).(Pittsburgh, 2003)Lujan Lujan et alet al.(Chicago, 2003).(Chicago, 2003)D’Souza D’Souza et alet al. (Houston, 2005). (Houston, 2005)

Adequate target coverageAdequate target coverageOARs sparingOARs sparing

Small bowelSmall bowel RectumRectum BladderBladder Bone marrowBone marrow

IMRT for GYN IMRT for GYN malignanciesmalignancies

Good clinical results with IMRT Good clinical results with IMRT 11 – 36 patients, whole-pelvis IMRT36 patients, whole-pelvis IMRT

Median FU = 19,6 monthMedian FU = 19,6 month

– 13.9% less GI-GII toxicity13.9% less GI-GII toxicity

– 3 year3 year Pelvic LC Pelvic LC 87,5%87,5% * (62 patients) * (62 patients) Cervix cancerCervix cancer 71% intact uterus71% intact uterus

1 Mundt et al. IJROBP, vol.56 #5 (2003) pp.1354-1360* Kochanski et al. ASTRO 2005 Abst #1114

Disadvantages of IMRTDisadvantages of IMRT Target volume definition Target volume definition

controversiescontroversies Impact ofImpact of

– Machine errors (MLC)Machine errors (MLC)– Patient positioning errors Patient positioning errors

Disadvantages of IMRTDisadvantages of IMRT Large # of segments and MULarge # of segments and MU

– Scattered doseScattered dose– Calculation uncertaintiesCalculation uncertainties

Time consumingTime consuming– PlanningPlanning– Treatment Treatment – Quality assuranceQuality assurance

Can we improve treatment Can we improve treatment delivery issues?delivery issues?

Ballista = Ballista = Aperture-based IMRTAperture-based IMRT

A feasability studyA feasability study- dosimetric- dosimetric- clinic- clinic

Let’s talk about IMRTLet’s talk about IMRT

Beamlet-basedBeamlet-based

vsvs

Aperture-basedAperture-based

Types of planningTypes of planning

Forward planningForward planning(conventional)(conventional)

– Manual (human) Manual (human) field definitionfield definition

– Followed by Followed by calculationcalculation

Inverse planning Inverse planning (IMRT)(IMRT)

– Dose objectives in Dose objectives in specific areas specific areas (contours)(contours)

– Solution found by Solution found by computer-assisted computer-assisted calculationcalculation

IMRTIMRT

Intensity Modulated Intensity Modulated

Radiation TherapyRadiation Therapy

Dose intensity varies inside the Dose intensity varies inside the beambeam– Several sub-fields (segments)Several sub-fields (segments)– Inverse planningInverse planning

No

Yes

Final plan

Does the plan meetthe clinical objectives?

Segmentation

Optimization of beamintensity profiles

Field geometry Basic objectives

Beamlet-based

IMRT

2nd

1st

*** Calculation steps

Aperture-based IMRTAperture-based IMRT

BallistaBallista 1 1

Inverse planning systemInverse planning system – Recently developed at L’Hotel-Dieu de Recently developed at L’Hotel-Dieu de

QcQc Intensity modulationIntensity modulation

– Anatomy-based MLC fieldAnatomy-based MLC field Simultaneous optimizationSimultaneous optimization

– Gantry, table and collimator anglesGantry, table and collimator angles– Wedge angle and beam weightsWedge angle and beam weights

1 BEAULIEU et al. Med.Phys.31, 1546-1557 (2004)

Aperture-basedSegmentation

Basic objectives Field geometry

Ballista

Anatomy-based fieldsAnatomy-based fields

Field weightsoptimization

Aperture-basedSegmentation

Basic objectives Field geometry

Ballista

Yes

Final plan

Does the plan meetthe clinical objectives?

No

Minor leafcorrections

Only

1

*** Calculation steps

X

Dosimetric studyDosimetric study

BallistaBallista for GYN for GYNPilot study -- Part IPilot study -- Part I

CHUQ -- Hotel-Dieu de Quebec CHUQ -- Hotel-Dieu de Quebec

Quebec cityQuebec city

Dosimetric objectivesDosimetric objectives EvaluateEvaluate Ballista Ballista as an alternative as an alternative

– Between 4-field and IMRTBetween 4-field and IMRT

– For post-operative whole-pelvis For post-operative whole-pelvis radiotherapy in gynecologic radiotherapy in gynecologic malignanciesmalignancies

HypothesisHypothesis Same target coverageSame target coverage

Organs at risk (OARs) sparingOrgans at risk (OARs) sparing– Better than 4-field Better than 4-field – As good as IMRT ?As good as IMRT ?

Treatment delivery advantagesTreatment delivery advantages

Materials and methodsMaterials and methods 10 patients10 patients

Endometrial or cervix malignanciesEndometrial or cervix malignancies

Post-operative external Post-operative external radiotherapyradiotherapy

45 Gy / 25 fractions, whole-pelvis45 Gy / 25 fractions, whole-pelvis+ brachy HDR boost+ brachy HDR boost

Materials and methodsMaterials and methods

For comparison purposes For comparison purposes

4 plans created for each patient4 plans created for each patient

Conventional 4-fieldConventional 4-field Enlarged 4-fieldEnlarged 4-field

– Results for OARs at same PTV Results for OARs at same PTV coveragecoverage

IMRTIMRT BallistaBallista

Inverse planning

Materials and Materials and methodsmethods

Forward planningForward planning

4-field4-field

enlarged 4-fieldenlarged 4-field

Materials and methodsMaterials and methods Planning CTscan as usualPlanning CTscan as usual

Conventional planning : Conventional planning : – 4-field plans based on bony landmarks4-field plans based on bony landmarks– Created before other plan conceptionCreated before other plan conception

Enlarged 4-fieldEnlarged 4-field– Aperture shaped to PTVAperture shaped to PTV

Materials and Materials and methodsmethods

Inverse planningInverse planning

IMRTIMRT

BallistaBallista

IMRTIMRT Plans created with PinnaclePlans created with Pinnacle3 3

systemsystem Step-and-shootStep-and-shoot 7 coplanar and equidistant 6 MV 7 coplanar and equidistant 6 MV

beamsbeams– 1 extraction1 extraction– 10-12 intensity levels10-12 intensity levels– Minimum field area = 4 cmMinimum field area = 4 cm22

Beam orientation for Beam orientation for Ballista Ballista plansplans

9 beams

23 MV

AnalysisAnalysis

For each plan (4) created For each plan (4) created for each patient (10)for each patient (10)

DVH DVH – PTV and OARsPTV and OARs

Number of segmentsNumber of segments Number of MUNumber of MU

Statistics : Student’s paired Statistics : Student’s paired tt-test-test

ResultsResults

Target coverageTarget coverage

4-field Enlarged 4-field

IMRT Ballista

PTV coverage / PTV coverage / homogeneityhomogeneity

4-field Enlarged4-field

IMRT Ballista

77%

p =0.03

(Mean±SEM, n=10)

ResultsResults

OARs sparingOARs sparing

RAR-B RAR-B 40 and 45 Gy40 and 45 Gy

+ 34.7 %

4-field Enlarged4-field

IMRT Ballista

(Mean±SEM, n=10)

For the same PTV coverage

RAR-BRAR-B

4-field Enlarged4-field

IMRT Ballista

+ 20.8 %

Ballista vs 4-field : V45 Gy, p < 0,001

(Mean±SEM, n=10)

RAR-BRAR-B

(Mean±SEM, n=10)

45 Gy : p = 0.15

40 Gy : p < 0.001 (diff. = 61.4 cm3 or 9.9% )

4-field Enlarged4-field

IMRT Ballista

(Mean±SEM, n=10)

ResultsResults

Treatment deliveryTreatment delivery

Number of segmentsNumber of segments

4-field4-field EnlargedEnlarged

4-field4-fieldIMRTIMRT BallistaBallista

44 44 128.6 ± 0.8 128.6 ± 0.8 33.3 ± 0.7 33.3 ± 0.7

(Mean±SEM, n=10)

Number of MUNumber of MUM

on

itor

Un

its

4-field

(Mean±SEM, n=10)

Calculated / delivered Calculated / delivered dosesdoses

Impact of leaf position errorsImpact of leaf position errors

± 1.4 Gy

DiscussionDiscussion

Advantages Advantages BallistaBallista vs IMRTvs IMRT

Number of segments reduced by Number of segments reduced by 75%75%

Number of MU reduced by 55%Number of MU reduced by 55%

Result in scattered radiation– risk of second malignancies– Concerns with 23 MV sec. neutrons…

Advantages Advantages BallistaBallista vs IMRTvs IMRT

Dose calculation + precise and + Dose calculation + precise and + robustrobust

treatment time treatment time (door-to-door)(door-to-door)

– 40-45 min IMRT – 20-25 min Ballista

quality assurance timequality assurance time– Dosimetric QA measurements can be Dosimetric QA measurements can be

avoidedavoided Larger segmentsLarger segments

IMRT for GYN IMRT for GYN malignanciesmalignancies

Post-operativePost-operative – More bowel to spareMore bowel to spare– Less organ motionLess organ motion

Main objective = Main objective = bowel sparingbowel sparing– Less bladder filling = more bowel to Less bladder filling = more bowel to

sparespare High sparing objectives on bladder tooHigh sparing objectives on bladder too

Movements vs shape of CTVMovements vs shape of CTV

Effect of AP-PA

rotation of the pelvis

Modified ImmobilizationModified Immobilization

Movements vs shape of CTVMovements vs shape of CTV

Effect of lateral

rotation

Less impact if spheric…

OARs resultsOARs results

To enhance sparing…To enhance sparing… Organ motion study necessary Organ motion study necessary 22

– To limit as possible expansion for PTVTo limit as possible expansion for PTV In our study, ITV/PTV limited sparing of In our study, ITV/PTV limited sparing of

rectum rectum

Optimal patient immobilizationOptimal patient immobilization– essentialessential

2 AHAMAD et al. (MDACC). IJROBP 62 (4) p.1117-1124 (2005)

ConclusionsConclusions

BallistaBallistaA new inverse planning approachA new inverse planning approach

Conclusions – Conclusions – BallistaBallista PTV coverage improvedPTV coverage improved

OARs sparingOARs sparing– Similar to IMRT planningSimilar to IMRT planning

Conclusions – Conclusions – BallistaBallista Advantages Advantages BallistaBallista vs IMRT vs IMRT

– Better dose calculation Better dose calculation – Less treatment timeLess treatment time– Less scattered doseLess scattered dose– Less quality assurance timeLess quality assurance time

Therapeutic ratio probably Therapeutic ratio probably improvedimproved

PerspectivesPerspectives Clinical results to comeClinical results to come 15 patients treated15 patients treated

– Acute toxicity analyzedAcute toxicity analyzed– Feasibility in a busy clinicFeasibility in a busy clinic

Anatomy-based Anatomy-based MLC Field Optimization MLC Field Optimization for the Treatment of for the Treatment of Gynecologic MalignanciesGynecologic Malignancies

Coauthors : Coauthors : Myriam Bouchard*Myriam Bouchard*Sylvain Nadeau*Sylvain Nadeau*Isabelle Germain* Isabelle Germain* Paul-Émile Raymond* Paul-Émile Raymond* François HarelFrançois HarelFrédéric Beaulieu** Frédéric Beaulieu** Luc Beaulieu*Luc Beaulieu*René Roy **René Roy **Luc Gingras**Luc Gingras**

ASTRO 2005ASTRO 2005AAPM 2005AAPM 2005CARO 2005CARO 2005COMP 2005COMP 2005SFRO 2005SFRO 2005AROQ 2005AROQ 2005

Questions : Questions : myriam.bouchard.1@ulaval.myriam.bouchard.1@ulaval.

caca

* Dep. of radiation oncology of L’Hotel-Dieu de Quebec, QC, * Dep. of radiation oncology of L’Hotel-Dieu de Quebec, QC, Canada Canada ** Dep. of Physics, Physics Engineering and Optics, Laval ** Dep. of Physics, Physics Engineering and Optics, Laval University, Quebec, CanadaUniversity, Quebec, Canada

ReferencesReferences Beaulieu Med.Phys. 31, 1546-1557

(2004) MundtMundt IJROBP 52 1330-1337 (200252 1330-1337 (2002)) Mundt Mundt IJROBP 56 1354-1360, (2003)56 1354-1360, (2003) Portelance Portelance IJROBP 51, 261-266 (200151, 261-266 (2001)) Ahamad (MDACC). IJROBP 62 (4) 1117-

24 (2005) Taylor IJROBP 63 (5) 1604- 12 (2005) Shih IJROBP 63 (4) 1262-69 (2005) Kochanski et al. ASTRO 2005 Abst #1114 Finlay Finlay IJROBP 64 (1) 205-09 (2006) 64 (1) 205-09 (2006)

AddendumAddendum

Bone marrowBone marrowDoses moyennes - moelle osseuse

V40Gy; 27,8

V40Gy; 46,2

V40Gy; 32,5 V40Gy; 36,4

0,010,020,030,040,050,060,070,080,090,0

100,0

4-champs 4-champs élargi IMRT Ballista

Vo

lum

e (%

)

V10Gy

V20Gy

V30Gy

V40Gy

V45Gy

V47.25Gy

4-field Enlarged 4-field

IMRT Ballista(Mean±SEM, n=10)

Enlarged 4-field vs Ballista : V40 Gy, p < 0,001 (for the same PTV coverage)

V 50% and V 95%V 50% and V 95%

0

2000

4000

6000

8000

10000

12000

1

Vol

ume

(cc)

4-champs

4-champs élarg.

IMRT

Ballista

Volume traitéVolume irradiéIrradiated volume Treated volume

4-field

Enlarged 4-f

(Mean±SEM, n=10)

Rectum – mean V 45 Rectum – mean V 45 GyGy

4-champs4-champs IMRTIMRT BallistaBallista p valuep value(difference)(difference)

61.7 %61.7 % 50.0%50.0% 59.9%59.9% NSNS(1.8%)(1.8%)

Rectum – mean V 45 Rectum – mean V 45 GyGy

4-champs4-champs IMRTIMRT BallistaBallista p valuep value(difference)(difference)

61.7 %61.7 % 50.0%50.0% 59.9%59.9% SSSS(9.9%)(9.9%)

Bladder – mean V 45 Bladder – mean V 45 GyGy

4-champs4-champs IMRTIMRT BallistaBallista p valuep value(difference)(difference)

91.3%91.3% 46.0%46.0% 47.8%47.8% SSSS(43.5%)(43.5%)

Bladder – mean V 45 Bladder – mean V 45 GyGy

4-champs4-champs IMRTIMRT BallistaBallista p valuep value(difference)(difference)

91.3%91.3% 46.0%46.0% 47.8%47.8% NSNS(1.8%)(1.8%)

• Number of fields• Gantry and table angle optimization

Feasibility

Selection of a fixed geometry (class solution)

Steps Result / conclusion

• Addition of sub- anatomic structures

New treatment that is comparable to IMRT

BallistaBallista

• Number of fields• Gantry and table angle optimization

Feasibility

Selection of a fixed geometry (class solution)

Steps Result / conclusion

• Addition of sub- anatomic structures

New treatment that is comparable to IMRT

BallistaBallista

Sub-anatomic Sub-anatomic structuresstructures