RapidArc/VMAT radiotherapy provides several benefits over conventional and IMRT treatments. Studies have shown that RapidArc plans improve tumor coverage and spare nearby healthy tissues better. It also reduces treatment times to only a few minutes compared to over 30 minutes for other techniques. Shorter treatment times mean less time for patient movement, improving accuracy and allowing clinics to treat more patients per day.

1. ANALYSIS OF BENEFITS OF RAPIDARC / VMAT
RADIOTHERAPYTREATMENT
WRITTEN BY MELISSA MCCLEMENT, APPLICATION SPECIALIST, TECMED AFRICA
DECEMBER 2011

2. INTRODUCTION
The firstRapidArcor VMAT treatmentinSouthAfricawas givenonthe 11th
of November2010, at
the RadiotherapyDepartmentof Netcare UnitasHospital. Since then,thisspecialityradiotherapy
treatmenthasonlygone fromstrengthto strength,withover400 patients inSouthAfricatreated
withthistechnique bythe endof 2011.
But the mainquestioniswhatexactlyisthe benefitof thisparticulartreatmenttechnique,in
comparisontothe conformal treatmenttechniques,tothe patientand ultimatelytothe
radiotherapydepartment?
Thisdocumentaimsto prove the benefitof RapidArc/VMATtreatmentincomparisontoconformal
radiotherapytreatmenttechniques. A descriptionof thistreatmenttechnique andcomparative
studieswill alsobe included.

3. WHAT IS RAPIDARC OR VMAT TREATMENT EXACTLY?
RapidArcisthe termcoinedbyVarianMedical SystemsforVolumetricModulatedArcTherapy
(VMAT). Asan employee of TecmedAfrica,distributorsof VarianRadiationequipment,Iwill use
RapidArcas my termof preference. The twocentresinSouthAfrica (Netcare Unitas andAddington
Hospital) doingVolumetricModulatedArcTherapyare alsoVarian/ Tecmeddepartments.
RapidArcradiotherapytechnologyadvancesthe standardof care withuncompromisedtreatmentin
twominutesorless(www.varian.com).
The Cancer Centre at Lake Manassas inVirginia,US,explainsRapidArcinthe followingmanner:
“RapidArcshapesandmodulatesahighlyfocussedtreatmentbeamsothatit targetsthe tumour
precisely,sparingsurroundinghealthytissues. Ittreatsthe entire tumourwithpinpointaccuracy
and iseasieronthe patient,whodoesnothave to holdstill forlongperiodsof time. RapidArc
treatmentallowsyourcliniciantodeliveramore targeteddose of radiation,withpotentiallyfewer
side effectsandlessdamage tohealthysurroundingtissue.”
One needstoput thisinlaymen’stermsthough.
Cancer cellsgrowanddivide more rapidlythanmanyof the normal cellsaroundthem. Highdosesof
radiationcan kill cellsorkeepthemfromgrowingand dividing,andtheyhave proventobe
particularlyeffectiveinkillingcancercellsandshrinkingtumours –cellsthatdivide andgrow quickly.
Althoughsome normal cellsare affectedbyradiation,mostnormal cellsrecovermore fullyfromthe
effectsof radiationthandocancer cells. Weekendrestbreaksallow normal cellstorecover. The
total dose of radiationandthe numberof treatmentsapatientneedsdependonthe size and
locationof the cancer, theytype of tumour,the patient’sgeneral health andotherfactors.
(www.cancer-radiation.com).
Where conventional radiotherapytechniquestreatone shapedfieldata certainangle andthen
move onto the nextangle totreat,RapidArcrotates360 degreesaroundthe patientatonce,whilst
enablingthe verysmall beamswithvaryingintensitytobe aimedatthe tumourfrommultiple
angles. Thismeansthathigherdosesof radiationare deliveredtohitthe tumourharder,and less
radiationisdeliveredtosurroundinghealthytissue. RapidArctreatmentsare plannedusing
sophisticatedcomputerprogramsthatanalyze diagnosticimage dataandcalculate the bestway of
deliveringthe radiationdosetominimize impactonhealthytissueforeachpatient. Asmentioned
before,treatmentsare fast. WithRapidArc,the treatmenttime isreducedbyabout80% in
comparisontoconventional treatmenttechniques.(www.altabatessummit.org).
Duringa RapidArctreatmentthe radiationbeamiscontinuallyshapedandreshapedaccordingto
the size,shape,andpositionof the tumourinthe body. The specializedsoftware algorithms
(mentionedearlieraswell) varythree parameterssimultaneously: the speedof rotationaroundthe
patient,the shape of the MLC aperture (inotherwordsthe shape of the beam),andthe dose
deliveryrate (inotherwordsthe dose deliveredatspecifictimes).(www.trinitascancercenter.org).

4. THE FACTS
Nowthat we knowexactly whatRapidArcis,we can compare the RapidArcplansto the more
conventional radiotherapyplansandeventoIMRT (IntensityModulatedRadiationTherapy) plans.
IMRT wasthe big precursorto RapidArc,andan enormousstepupfromconventional radiotherapy
plans.
All of the followingstudiesare attachedunderAPPENDIX A.
1) VUmc in AmsterdamcomparedRapidArctoIMRT planningforHeadand Neck,gliomaand
pancreaticcancers. TheyfoundthatRapidArcaccuratelydeliversthe planneddose
distributions. Plansof 2arcs were superiortoIMRT for tumourvolume homogeneityandfor
sparingof the organsat risk. Giventhe low numberof MU’s and short deliverytimes,
RapidArchas replacedIMRTin theirdepartment.
2) In anotherstudybyVUmc, where RapidArcforhighlyconformal irradiationof vestibular
schwannoma’swere investigated,theyconcludedthatwithRapidArc,ahigherconformity
index,adecrease inlowdose areaandshortertreatmentdeliverytimeswereshown. That
indicatesRapidArcto be a patient-friendly,non-invasive alternative to“conventional”5-arc
radiosurgeryforvestibularschwannoma.(Radiosurgeryisasingle highdose treatmentwith
pencil thinbeamsforverysmall sizedtumoursinthe brain).
3) In the firstsix monthsof goingclinical withRapidArc,the OncologyInstituteof Southern
SwitzerlandinBellinzonafoundthatthe targetcoverage isD₉₈ > 93% withhighsparingof
organs at risk. The beamontime was around1 minute 20 seconds,andthe average time a
patientspentinthe treatmentroomwas7.5 minutes. TheyexpectthatRapidArcwould
progressivelyreplace IMRTinmost of theirclinical indications.
4) The same institute foundthatsimultaneouslytreatinganintegratedboostforbilateral
breastcarcinoma withRapidArcshoweddosimetricimprovementswithrespecttoIMRT and
that deliveryparametersconfirmeditslogistical advantages. Treatingbreastcarcinomain
thisway woulddecrease the amountof treatmentfractions,aswithconventional treatment
the whole breast istreatedfirst,followedbythe boost.
5) In anotherstudybythe OncologyInstituteof SouthernSwitzerland,RapidArcwas
investigatedforanal canal cancer incomparisonto IMRT. Theyfoundthat although
excellentdosimetricresultswereachievedwithIMRT,RapidArcwithdouble arcsimproved
the sparingof organsat risk andhad uncompromisedtarget(tumourvolume)coverage.
6) Whena studybetweenthree departments(OncologyInstitute of SouthernSwitzerland,
Universityof Lausanne andTata Memorial Hospital inMumbai) were done oncervix uteri
treatments,the conclusionwasthatstatisticallyhighlysignificantimprovementsinorgansat
riskand healthytissue sparingwithuncompromisedtargetcoverage wasfoundwith
RapidArc,whichleadtoavoidance of treatmentswithconventional IMRT.

5. 7) The departmentof RadiationOncologyinMontpellier,France,alsofoundthattreatmentto
the headand neckusingRapidArcreducestreatmenttime andthe numberof monitorunits.
Theyalsofoundthat the dose deliveryto bothparotidswassignificantlydecreased.
8) The same departmentalsocomparedplansusingRapidArcandIMRT for anal cancer
treatment. TheirconclusionwasthatRapidArcwasable to deliver anequivalenttreatment
planto IMRT intermsof tumourvolume coverage andsparingof organsat risk. But,the
significantreductioninMU’sand treatmenttime perfractionmaydecrease the riskof
secondarymalignancycomparedtoIMRT.
As mentionedbefore,all of the above studiesare includedinAPPENDIX A.

6. THE REASONING
There are manycentresthat came to the same conclusions:
- Lesstime for the patientonthe bed,meanslessmovement,whichwouldincreasethe
accuracy of the treatment(www.cancer-radiation.com).
Significance toadepartment:
1) Patientmovementonthe bedwhilstirradiatingdoesnotonlymeanmissingthe target
volume (tumourvolume),butalsoincreasingthe dose deliveredtothe normal or healthy
tissues. Underdosingthe targetvolume wouldleadtorecurrence,overdosingthe normal
tissueswouldleadtoincreasedside effects(bothearlyandlate side effects). The next
dominotofall inthe line wouldbe thatany of the resultingissueswouldleadtoanincrease
inthe use of medical resources.
2) The lessthe time perpatientspendsonthe treatmentbed,the more patientscanbe
treatedinone day. Thusleadingtoeliminatingwaitinglists.
- The significantdecrease inthe amountof monitorunits(MU) neededpertreatment.
Significance toadepartment:
As the lastmentionedstudyconfirmed,aRapidArctreatmentneedslessMU thanan IMRT
treatmentwithessentiallythe same conformitytothe tumourvolume (againleadingtoless
irradiationof normal tissues). Anincrease amountof MU couldpossiblyleadtoa secondary
tumourdeveloping –leading,yetagain,tothe use of more medical resources.
- The abilitytotreat a large fieldanda boostto the same area simultaneously.
The above was notmentionedinanyof the studiesincludedinthisdocument. Itispossible
to treat multiplesmall tumours,locatedinthe same anatomical area,toa higherdose,
withinalargeranatomical tumourvolume. Forexample: The boostarea of a breast patient
can be treatedtothe higherdose whilstthe whole of the breastisbeingtreatedtoalower
dose;Includingpara-aorticnodesinapelvictreatmentvolume;Multiplebrainmetastases
includedinone braintreatmentvolume.
Significance toadepartment:
The more fractionsaddedtoa treatmentvolume,the longerthe patientisbeingtreated.
Treatingmore than one volume atone time or partsof a volume toa higherdose at once,
will decrease the amountof treatmentfractionsneeded,thusdecreasingthe total time the
patientoccupiesthe slotonthe treatmentunit. Indepartmentswhere thereisabacklogof
patientstobe treated,thisisverysignificant. Thattreatmentslotwill thenbe filledwitha
newpatientquickerandmore often,thusresultinginmore patientsbeingtreatedperday,
or per month,or peryear.

7. - The dose to the organs at risk wasdecreasedinall of the studiesmentioned. The organsat
riskare usuallytreateddifferentlyto‘normal tissue’.Organsatriskare those organswhich
has a thresholddose limitbefore irreversibledamage iscaused. Fora treatment tothe
brain,one of the organsat riskwouldbe the lensesof the eyes,astheycanhandle onlyvery
little amountsof radiationbefore causing permanentblindness. Anotherorganatriskwould
be the brainstem,whichcanalsoonlyhandle acertainamount of dose before causingmajor
side effects. The spine canonlyhandle acertainamountof radiationbefore irreversible
paralysisiscaused.
Significance toadepartment:
It is obviousthatseriousdamage,suchasparalysisorblindnessoremphysemacausedby
‘overdosing’anorganat risk,will increase the futurefinancial pressure putonmedical
resources.
APPENDIX Bincludesanindicationof the extensive clinical applicationsof RapidArc.

8. CONCLUSION
In conclusion,one hastoadmit that providingthe best,mostrelevantandmosteffective
radiotherapytreatmentavailable toapatientisof the utmostimportance. The longterm
benefitsthatresultfromahighlyadvancedtreatmentsuchasRapidArcor VMATare
pricelesstoapatient. The departmental benefitscanof course alsonot be overlooked –
more patientscanbe treatedina givenamountof time thanthat withconventional
treatmentorIMRT. RapidArcisthe future of Radiationtherapy.

9. APPENDIX A: STUDIES MENTIONED WITHIN TEXT
IN ORDER OF DISCUSSION WITHIN TEXT

15. APPENDIX B: ILLUSTRATION OF EXTENSIVE CLINICAL APPLICATION OF RAPIDARC