w w w . j c o l . o r g . b r
Journal
of
Coloproctology
Review
Article
Anal
canal
squamous
carcinoma
夽
Maricruz
Nunes
Magalhães
a,∗,
Laura
Elisabete
Ribeiro
Barbosa
baUniversidadedoPorto,FaculdadedeMedicina,Porto,Portugal
bUniversidadedoPorto,FaculdadedeMedicina,CentroHospitalarSãoJoão,Servic¸odeCirurgiaGeral,Porto,Portugal
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received21June2016
Accepted24August2016
Availableonline17September2016
Keywords:
Squamouscellcarcinoma
Analcanal
HPV HIV
a
b
s
t
r
a
c
t
Background:Analcanalcarcinoma isa rareneoplasm, representing2%ofthe digestive
tumors,andthemostcommonissquamouscellcarcinoma,withanincreasingincidence.
Objective:Thestudyaimstoelucidatethepathogenesisofanincreasinglyprevalentdisease,
aswellastoupdatetreatmentandprognosis.
Methods:AliteraturesearchinPubmeddatabase,includingarticlesfrom2005to2015and
cross-researcharticleswiththeinitialresearch.
Results:SeveralstudiesprovetheroleofHPVasamajorriskfactorinthedevelopment
ofsquamouscellcarcinomaofanalcanal,aswellasagreaterprevalenceofthis
neopla-siainHIV-positivepeopleandinthosewhopracticereceptiveanalintercourse.Inthelast
twodecadeschemoradiotherapyremainsthetreatmentofchoice,andabdominoperineal
resectionisreservedforthosecasesoftreatmentfailureorrecurrence.Evidenceadvances
inordertoadaptthetreatmenttoeachpatient,takingintoaccountindividualprognostic
factorsandbiologicaltumorcharacteristics.
Conclusions:SquamouscellcarcinomaoftheanalcanalisaneoplasmassociatedwithHPV;
therefore,screeningandvaccinationprogramsofmaleindividuals,bywayofprevention,
shouldbestarted.Manystudiesareneededinordertoachievedevelopmentinthetreatment
aswellasintheevaluationofthebiologicalcharacteristicsofthetumor.
©2016SociedadeBrasileiradeColoproctologia.PublishedbyElsevierEditoraLtda.This
isanopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/
licenses/by-nc-nd/4.0/).
Carcinoma
epidermóide
do
canal
anal
Palavras-chave:
Carcinomaescamoso
Canalanal
HPV HIV
r
e
s
u
m
o
Introduc¸ão:Ocarcinomadocanalanaléumaneoplasiarara,representando2%dostumores
digestivos,sendooepidermóideomaiscomumcomumaincidênciacrescente.
Objetivo:Esteestudopretendeelucidarsobreaetiopatogeniadestapatologiacadavezmais
prevalente,assimcomoatualizarsobreotratamentoeprognóstico.
Métodos:PesquisabibliográficanabasededadosPubmed,incluindoartigosde2005a2015,
assimcomoartigosdepesquisacruzadacomosartigosiniciais.
夽
StudyconductedattheDepartamentodeCirurgia,FaculdadedeMedicina,UniversidadedoPorto,Porto,Portugal.
∗ Correspondingauthor.
E-mail:maricruznunes@live.com.pt(M.N.Magalhães).
http://dx.doi.org/10.1016/j.jcol.2016.08.003
2237-9363/©2016SociedadeBrasileiradeColoproctologia.PublishedbyElsevierEditoraLtda.ThisisanopenaccessarticleundertheCC
Resultados: DiversosestudosprovamopapeldoHPV comoumfatorderiscomajorno
desenvolvimentodecarcinomaepidermóidedocanal,assimcomoumamaiorprevalência
destaneoplasianapopulac¸ãoHIVpositivaenosquepraticamsexoanalrecetivo.O
trata-mentocontinuaaserdesdeháduasdécadasaquimioradioterapia,reservandoaressec¸ão
abdominoperinealparacasosdefalênciadotratamentoourecorrência.Aevidênciaavanc¸a
nosentidodeadequarotratamentoacadadoente,tendoemcontafatoresprognósticos
individuaiseascaracterísticasbiológicasdotumor.
Conclusões: OcarcinomaepidermóidedocanalanaléumaneoplasiaassociadaaoHPV,
logodeveriainiciar-seprogramasderastreioevacinarosexomasculinocomoprevenc¸ão.
Muitosestudossãonecessáriosparaevoluirnotratamento,assimcomonaavaliac¸ãodas
característicasbiológicasdotumor.
©2016SociedadeBrasileiradeColoproctologia.PublicadoporElsevierEditoraLtda.Este
´eumartigoOpenAccesssobumalicenc¸aCCBY-NC-ND(http://creativecommons.org/
licenses/by-nc-nd/4.0/).
Introduction
Anatomyandhistologyoftheanalcanal
Theanalcanalmeasuresapproximately4cminlength,being
shorterinwomen.Thischannelisthelower portionofthe
gastrointestinaltract.1Itssurgicalmarginsaretheanalverge
distallyandtheanorectaljunctionproximally.1,2
Histologically,intheanalcanal,onecanfindseveraltypes
ofepithelia.1,2 Proximally,thechannel isformedby
colum-narepitheliumsimilartotheintestinalepithelium,which,in
theanalcanal,hasfoldsinthemucousmembraneforming
theanalcolumns.Thesecolumnsareconnectedtransversely
byfolds called anal valves, which, together constitute the
pectinealline.1,2 Thenon-keratinizedsquamousepithelium
thatislocateddistallytothepectineallinelackshair
folli-clesandsebaceousandsweatglands,unlikethekeratinized
epitheliumwhichiscontinuousintheanalverge.1–4in
addi-tion, between the pectineal line and the non-keratinized
squamousepitheliumthereisatransitionzoneinwhichthe
epitheliummaybeofthecolumnar,cubic,transitional(asin
bladder),orsquamoustype.Thistransitionzoneisvery
spe-cifictotheanalarea,andmayalsobecalledofcloacogenic
zone,forembryologicalreasons.1–4
Classificationofneoplasmsoftheanalcanal
Classically,thegenericterm“anus”comprisestheanalcanal
andtheanalverge.5Thus,neoplasmsofthiszonearedivided
betweenthesetwolocations.5Thetumorsoftheanalverge,
knownasperianalcancers,areidenticaltosquamousor
epi-dermoidcutaneoustumors,andthereforedonotenterinto
theWorldHealthOrganization(WHO)classificationof
diges-tivetumors.5Inviewofthelackofclaritybetweentumorsof
theanalcanalandanalverge,WHOhasproposedapragmatic
definition,statingthat“atumoroftheanalcanalisatumor
thatcannotbeseenentirelywiththehelpofasubtlepullof
thebuttocks”.5 There are several typesoftumors,
depend-ingonthetypeofepitheliuminvolved,includingsquamous
or epidermoid tumor, which is the predominant
histo-logictype,whileotherrarertypesincludeadenocarcinoma,
neuroendocrinetumors,stromaltumors,lymphomasand
sec-ondarytumors.5
Giventhesimilaritiesbetweentheepidermoidcarcinoma
oftheanalcanalandthatoftheuterinecervix,thereisa
cyto-logicalandhistologicalclassificationforanallesionssimilarto
theclassificationforthecervix.6ThemodifiedBethesda
cyto-logical classificationsystemdivides squamousanal lesions
into high- and low-grade intraepithelial lesions, and these
lesionsstillhaveintermediateclassifications,called“probable
low-andhigh-gradelesions”.6Thereisalsoaclassificationof
invasivesquamouscellcarcinoma.6
Despite the high malignant potential of the high-grade
intraepitheliallesions,7lessthan1%peryearwillprogressto
cancer.3
Epidemiologyofanalcanalneoplasms
Malignant tumorsof the anal canal represent 0.43% of all
malignancies and 2%ofthe digestive malignant tumors.5,8
Overall,themostprevalentcanceroftheanalcanalis
squa-mous cell carcinoma (85%), followed by adenocarcinoma
(10%).Theothertypesarerare,representinglessthan5%of
alldiagnosedtumorsoftheanalcanal.8
Analcancerincreasedby50%overthepast25years,but
thisisstillarareneoplasm.6Itsannualincidencehasbeenof
1in100,000people,andishigherinwomen.Inthelasttwo
decades,asignificantmodificationinsurvivalafter5yearswas
notobserved,rangingfrom66%to44%inCentralandEastern
Europe,respectively.9
Mostexistingepidemiologicalinformationrefersto
squa-mous cell carcinoma. Thus, according to statistics, the
squamous cell type is more prevalent in women, its risk
increaseswithage(theaverageageatdiagnosisis60years)
and when it occurs in young, often these patients are
immunocompromised.5However,theoccurrenceofdiagnoses
inincreasinglyyoungerpeoplehasbeenfound.6
Methods
The literature survey was conducted inPubmed database.
Thephrases“epidermoidcarcinomaoftheanal canal”and
articlespublishedfrom2005to2015andperformedinhumans
wereconsidered.AlanguagefilterforsearchonlyinEnglish,
Portugueseand Spanishwasincluded.Opinionarticlesand
letterstotheauthorswereexcluded.Afterreadingthetitle
andabstract,andsubjecttoanavailabilityofthearticle,36
articleswereobtainedinPubmed.Articlesobtainedby
cross-searchingwiththearticlesoftheinitialresearchandbooks
withrelevantinformationwerealsoadded.
Results
Etiologyandpathogenesisofsquamouscellcarcinoma
Someriskfactorshavebeensuggestedforthedevelopment
ofthis neoplasm, particularlyfemale gender, Human
pap-illomavirus (HPV) infection,history ofsexually transmitted
disease,a number greater than 10 sexual partners,
recep-tive anal sex history, previous history of warts or genital
malignancyinjuries, Human immunodeficiency virus (HIV)
infection,immunosuppression,smoking,andprolongeduse
ofcorticosteroids.3,4
Overtheyears,ithasbeenfoundthatHPVinfectionisan
importantcause.10Ouhoummaneetal.,inastudyconducted
inQuebec,obtainedresultsfavoringthishypothesis.11
Ninety-twopercentofcasesofepidermoidcarcinomawerecolonized
withHPV,andthemostprevalenttypewasHPV16.11
HPVinfectionisthemostprevalentsexuallytransmitted
disease.12 Thisagent isa double-strandedDNA virus with
160differenttypesdescribedandwithspecifictissuetropism.
Thirtytypesexhibittropismforanogenitalepithelium,and
types16and18arethosewithgreatermalignantpotential,
althoughtheyarealsoinvolvedinbenignlesions.12
Thepathogenesisofthe lesionscausedbythis agentin
theanal canalhasbeenrelated tothepathogenesisinthe
uterinecervix.10 Similartowhathappensinthecervix,the
carcinogenesisintheanalcanalbyHPVcoursesthefollowing
timesequence:Infection,persistenceofinfection,dysplasia
development,andprogressiontoaninvasivecancer.10These
stepscanbereversedbytheregressionoftheinfection.10
AlthoughtheHPVlifecycleintheepitheliumofthecervix
and in the anal canal is the same, the natural history of
theintraepitheliallesionsisnotidentical,sincetheanatomy,
physiology,andimmuneresponsearedifferentinthecervix
andintheanalcanal.6
Initially, themethod thatthe virus uses tocolonizethe
hostisto evadethe innateimmunity mechanisms,
partic-ularly the physicalbarrier, antimicrobial peptides, Toll-like
receptors,andvarious immunecells.6 Circumventing these
mechanismsdelaysactivationofadaptiveimmunity,6which
facilitatesvirusentryintocells.Byintegratingintothehost
genome,the viruswillcausecellularchanges thatare
pre-dominantly theresponsibility oftwoviral proteins,E6and
E7.13Oneofthemechanisms usedtomodifythe cellcycle
isthealterationoftumorsuppressorgenes.13p16(inhibitor
of kinase 4), a cell-cycle regulatory protein, interacts with
CDK4and CDK6inhibiting the bindingofthesesubstances
tocyclinDandconsequentlyreducingitskinaseactivity.This
inhibitionpreventsthe phosphorylationofRbprotein,thus
inhibitingthetranscriptionalactivationbytheE2Fcomplex,
which,inturn,preventsthepassageofG1totheSphaseof
thecellcycle.14TheE7protein,byintegratingintothegenome,
changes thenormalp16proteinfunctioning.6Onthe other
hand,E6isresponsibleforsuppressingthenormalfunctioning
ofp53,anotherregulatoryproteinofthecellcycleand
respon-sible foractivating the transcription ofgenes that encode
p16-likeproteins.6E6proteinalsopromotestheactivationof
telomerase,perpetuatingthetransformationand
immortal-izationofthecell.6
The changeof p16and p53 expressionhasbeen linked
toHPV,tothepointofdifferentiatingHPV-positiveand
HPV-negativecanceroftheanalcanalbasedonthederegulationof
theexpressionofthesegenes.13Theexpressionofp16isthe
mostaffectedincasesofHPVinfection,whilep53mutation
isassociatedwithHPV-negativecarcinoma.15Thisdistinction
betweenHPV-positiveandHPV-negativecarcinomaprovesto
beimportantbecausethereisadirectimplicationofthe
bio-logicaldifferencesbetweenthetwotypesintheresponseto
treatmentandinprognosis.13
Asalreadymentionedinthispaper,HIVinfectionisarisk
factorforsquamouscellcarcinoma.10Evennotbeinga
pri-maryetiologicagent,HIVisaco-infectionmarkerforother
sexuallytransmitteddiseases,includingHPV,10andonemay
observe a high prevalence of co-infection by HPV in
HIV-positivepopulations.16However,notallpatientsinfectedwith
HPVdevelopintraepitheliallesionsresultingfrominfection.6
Overtheyearsandespeciallyintheeraofantiretroviral
ther-apy, the carcinoma epidermoid of anal canal has become
the more prevalent acquired immunodeficiency syndrome
(AIDS)non-definingneoplasminHIV-positiveadultsubjects,
being30timesmoreprevalentinthispopulationthaninthe
generalpopulation.6 inaddition tothe higherincidencein
relationtothegeneralpopulation,patientswithHIValsoshow
higherlikelihoodofprogressiontoahigh-grade,
intraepithe-liallesion-invasive,analcarcinoma.17
Anotheralreadycitedriskfactoristhepracticeofreceptive
analintercourse.6Somestudieshavecomparedthefrequency
ofhigh-gradeintraepithelialanallesionsinHIV-positiveand
HIV-negative menwho haveanal sexwithothermen, and
theresultsrevealednosignificantdifferencebetweenthese
groups.6 This finding may suggest that the immunological
deficits in HIVinfection may not playsucha decisive role
ashadbeenpreviouslythoughtinthedevelopmentof
high-gradelesionsthroughhigh-riskHPV.6Somestudiesconducted
specificallywithHPV16foundthatincertainvariantsofthe
virusthereisaprogressiontocarcinomawhetherornotin
the presence ofHIV infection and irrespective of CD4+
T-lymphocytecount.6
Thosestudieswhichwereconductedinordertoevaluate
theimpactoftheimmunesystem,particularlyofregulatory
CD4+ T cells,in HPV infection, focused on intra-epithelial
lesionsandoncarcinomasoftheuterinecervix.6These
stud-ies showed that these cells play an important role in the
regressionofinfection,andconsequentlyinthelesionscaused
byHPV,especiallyHPVtype16.6Therefore,giventhattheHIV
infection induces immunodeficiency in CD4+ lymphocytes,
theHIVinfectionisconsideredasariskfactorforinfection
byHPV,forintraepitheliallesionsandforinvasiveanal
car-cinoma, takinginto accounttheroleofCD4+Tcellsinthe
authorssticktothehypothesisthatthereareother
determi-nantsinthecarcinogenesisprocess,6takingintoaccountthat
theantiretroviraltherapydidnotreducetheincidenceofanal
cancerinpeoplewithHIV.18
Preventionandscreening
Theidentificationofamajoretiologicalagent,suchasHPV,has
allowedthedevelopmentofavaccinepreventinginfectionby
certainstrains,particularlythemostcommonand
pathologi-cal,andconcomitantlypreventingsquamouscellcarcinoma.9
Thisvaccinehasbeendevelopedinordertopreventcarcinoma
ofthecervix,however,itisanticipateditalsoprevents80%of
analcarcinomata.9
Basedontheresultsofcervicalcytologyintheprevention
ofcervixcarcinoma,screeningprogramswithanal cytology
and high-resolution anoscopy have been proposed forrisk
groupsforanalcancer,includingindividualspracticing
recep-tiveanal sex, HIV patients, and patientswith a history of
anogenitalmalignanciescausedbyHPV.9Inconjunctionwith
thehigh-resolutionanoscopy,onecanaddaceticacid,which
differentiateslow-andhigh-gradeintraepitheliallesions,
sta-ining in white color those precursor lesions of high-grade
dysplasia.19
Thescreeningcanenabletheidentificationof
malignan-ciesintheir earlystageand atimelytreatment, aswell as
thediagnosisofthoseprecursorintraepitheliallesions,often
asymptomatic.20
Anal cytology haslow sensitivitybut greatspecificity.21
Inadequatespecimencollectioncontinuestobeamajor
limi-tationofthistest,andthisprocedureshouldbeimprovedfor
makingtheanalcytologyarecommendedscreeningtestfor
allpatientsatriskofanalcarcinoma.21
Diagnosis
Clinical history isalways critical, regardlessof the area of
medicine,andanalcancerisnoexception.Onemust
deter-mine all the symptoms and predisponent riskfactors that
couldsuggestthisdiagnosis.9
Anal carcinoma is characterized by an indolent
natu-ralhistory,9 withapresentationofanal bleeding,the most
commonsymptom,3oftenconfusedwithableedingof
hem-orrhoidalorigin,whichdelaysdiagnosis.9 Thesecond most
common symptom isproctalgia,3 which may be
accompa-niedbyamass,anulcerwhichdoesnotheal,itching,mucus
emission,fecalincontinence,andfistulae.9However,20%of
patientsareasymptomaticatdiagnosis.22
Currently,therecommendeddiagnostictestsarethe
digi-talrectalexaminationandproctoscopy,thatshouldbecarried
outbyanexpertdoctorand,ifnecessary,undersedationto
allowforanadequate histologicalbiopsy,a criticalstep to
diagnosis.9,23Additionally,adiagnostictestforHIVandaCD4+
T-lymphocytecountshouldbecarriedout.23
The gynecological exam is an important procedure for
female patients, in order to evaluate vaginal involvement,
especiallyinlowerandearliertumors,aswellastoruleoutthe
presenceoffistulae.9Thegynecologicevaluationisalso
impor-tantbecause oftensynchronous andmetachronous genital
neoplasmsrelatedtoHPVdevelopinthecontextofananal
squamouscellcarcinomainwomen.9Acytologytestforcervix
cancerscreeningshouldalsobeheld.23
Staging
For thestagingofneoplasia,theTNMsystemisused.This
systemisbasedontumorsize(T),onregionalnodular
involve-ment (N),and on thepresenceofmetastasis(M).9 Nodular
involvementisassessedtakingintoaccountthedistanceto
theprimarysiteandnotthenumberofnodesinvolved.9
Imagingevaluationisessentialtoassesslocalinvolvement,
withthehelpofnuclearmagneticresonance(NMR)imagesor
ofanendoanalpelvicechography,aprocedurequiteeffective
todeterminethetransmuraldepthofthetumor,especiallyin
thecaseofsmallT1lesions,wherethisprocedureshowsbetter
accuracy.9Withmagneticresonance,onecanobtain
informa-tiononthesizeofthetumor,invasionofadjacentorgans,and
nodularinvolvement.9
Obtainingathoracicandabdominalcomputedtomography
(CT)isalsodesirable,inordertodetectdistantmetastases,9,23
which are present at diagnosis in 5–8% of cases.9 On the
otherhand,onecanalsoconsideraPET(positronemission
tomography)study,althoughthisdoesnotreplaceaCTscan.23
However,whenthisprocedureisperformedwith
fluorodeoxy-glucose,showshighsensitivitytodetectnodularinvolvement,
suchthat severalstudies havedemonstrated ashift inthe
tumorstagein20%ofcases.9,22Whenthisoccurs,thetrend
isinfavorofincreasingthestage,whichchangesthe
treat-ment plan andinfluencing particularly the radiotherapyin
approximately3–5%ofcases.9Thistechniqueisofimportance
becauseatdiagnosisnodalinvolvementisfoundin30–40%of
cases.9Additionally,anassessmentbypalpationofthe
pres-enceofinguinaladenopathy,particularlysurfaceandmedial
ones,9,23iscritical;ifdetected,theseinjuriesshouldbe
biop-sied byfine-needle aspiration,23 aswell asthoseincreased
nodeswithmorethan10mm,detectedonimagingstudies.9
Inguinallymphinvolvementisanindependent
prognos-tic factor in patients with anal carcinoma.24 Therefore, to
improvethediagnosticaccuracywithrespecttonode
involve-mentandradiotherapyregime,JohnSprattin2000proposed
asentinellymphaticnodebiopsyasadiagnostictestof
gan-glionmicro-metastases.25Atthesametime,Sprattsuggested
thattheprophylacticsurgicaldissectionoftheinguinallymph
nodesisnotrequired,butmaybecurativeinmanycaseswith
nodularinvolvementorwhichpresentapositivesentinelnode
biopsy.25However,duetothehighfalse-negativeratefoundin
somestudies,thisprocedureisnotyetpartoftheroutinetests
advised.24However,Mistrangeloetal.,in2013,inthestudyin
whichareviewofclinicaltrialsthatassesstheprecisionof
thistechniquewasperformed,obtainedafalsenegativerate
of3.7%,whichwasconsideredacceptable.Theseauthors
con-cludedthattheprocedurecanbeperformedinpatientswith
analcarcinomaandthatthisisaneasyandperfectlyfeasible
technique,withahighdetectionrateof98.4%reportedinthe
literature.24
Treatmentandcomplications
Themaingoaloftreatmentistoobtainacurewith
sphincterfunctionandmaintainingthebestpossiblequality
oflife.9
Treatmentofsquamouscellcarcinomaoftheanalcanal
requiresamultidisciplinaryapproach,essentiallywheninthe
presenceof a state ofimmunosuppression.26 The
involve-ment ofradiotherapists, oncologists,surgeons, radiologists
andpathologistsismandatory.9
Initially,uptothe1980ssurgerywasthetreatmentforall
analcarcinomas,mainlywithabdominoperinealresection.9,23
Severalstudiescarriedoutinthe1970s26promptedthe
pub-licationbyNigroet al.in1983ofastudywhich concluded
thatcombinationtherapywithchemotherapyandradiation
therapywaseffectiveenoughtodismisssurgeryiftheinjury
wouldhavecompletelyregressed,andthatthiswasproven
through appropriatediagnostic ancillary laboratory tests.27
Thisconservativetherapeuticstrategyallowedanexcellent
localcontrol,disease-freesurvival,andqualityoflife.27
Theexclusiveuseofsurgeryhasahighrecurrenceanda
survivalat5yearsof30–70%.23Thisstrategyalsopresentsthe
disadvantagesofapermanent colostomy andhigh ratesof
genitourinarycomplications.23Chemoradiotherapyhasgiven
betterresultsversussurgery,withfewercomplicationsanda
survivalat5yearsof61–85%.18
Thus, the standard treatment for non-metastatic
squa-mous cell carcinoma of the anal canal has been a
combinationtherapy,withchemotherapyusing5-fluorouracil
(5FU)750mg/m2/daybycontinuousinfusionandmitomycin
C(MMC)12mg/m2onday1ofeachcycle,23andradiotherapy
witharadiationtypicallybetween50and54Gy,26providinga
completeregressionin80–90%ofpatients.9These
recommen-dationsarebasedonsixmulticenterclinicaltrialsevaluating
theresultsofthecombinedtreatment.28
Abdominoperinealresectionandpermanentcolostomyare
proceduresreserved forpatientswithresidual or recurrent
diseaseafteracompletetreatmentofchemoradiotherapy.29
Surgeryafterrecurrenceallowsalocalcontrolin60%ofcases
andasurvivalat5yearsof30–60%.9Thefactthatwearein
faceofaradicalsurgicalintervention,inanirradiatedsite,
increasestheriskofcomplicationsofthesurgicalwound.26
Inordertominimize thesecomplications,amyocutaneous
reconstructionusingtherectusabdominismusclecanbeheld,
andthatwasshowntobeaneffectivetechnique.26
Theriskofneedingapermanentcolostomyhasbeen
eval-uatedinseveralstudies,withtheconclusionthatthereare
pretreatmentindependentriskfactors,particularlymale
gen-der,tumorsize,andhemoglobinlevels,thatmayproveuseful
forpredictionofcombinationtherapyfailure,withthe
possi-bilityofofferingtothesepatientsthesurgicaltreatmentasan
initialtherapy.30
One consideration that must be borne in mind during
treatment is HIV infection.26 Other than
immunosuppres-sion, these patients show little tolerance tothe treatment
andapoorertoxicityprofile.26Somestudieshavefoundthat
HIV-positivepatientshaveaworseprognosiswith
chemora-diotherapythanHIV-negativepatients.31Oneoftheproblems
withthetreatmentarethehighdosesofradiation,poorly
tol-eratedbypatientswithHIV.Somestudieshaveproposedto
reducethe dose commonlyused infavorofless toxic
lev-elsthatcould simultaneouslyachieve theregression ofthe
neoplasm.26Mostofthesepatientswhoshowedaprofileof
little tolerance with routine radiation levels had a low
CD4+cell count.26Thus,somestudiessuggestinitiatingan
antiretroviraltherapyinordertoincreasethepatient’sCD4+
cellcounttomorethan200cells/L,beforestartingthe
treat-ment foranalcarcinoma.23,28 Thisstrategy issupportedby
Wexleretal., that,intheirstudy,obtainedtherapeutic
out-comessimilarbothinHIV-negativeandHIV-positivepatients
treatedwithantiretroviraltherapy.32However,theseauthors
found significant toxicity in HIV-positivepatients with the
standardizedtreatmentforanalcarcinoma,despitethe
con-trolledviralloadlevelsandCD4+cellcounts.32Ontheother
hand,evidencesuggeststhataftertheimplementationofthe
appropriatetreatmentoftheHIVinfection,thetreatmentfor
analcarcinomaisstandardized,thatis,acombination
ther-apyusing5-FUand,andradiotherapywithnormalradiation
doses.28,33
Although we refer to the usual doses of radiation, the
truthisthattheoptimaldoseofradiationhasnotyetbeen
established, nor the ideal scheme.28,34 There are different
approachestoradiationtherapy,butingeneralconventional
radiotherapyencompassesprimarytumorandaffectedlocal
lymph nodes.9 A number ofstudies suggest that the
opti-maldoseofradiationvarieswiththetumor;therearetumors
thatneedahigherdose,aswellasothers thatmayregress
atalowerdose.35Thus,abiomarkerwouldbeusefulforthe
predictionoftumorresponse.Accordingly,multi-parameter
magneticresonanceisusedassuchinothersquamous
car-cinomas during chemoradiotherapy, and there is evidence
which suggestsits effectivenessinthe anal squamous
car-cinoma as a predictor of the individual patient response,
allowinganadjustmentofthedoseandoftheradiation
ther-apyregimen.35
Another group thatshould betaken into accountwhen
usingradiotherapyaretheelderly,asthisagegroupmaynot
toleratethefulldoseofradiationcommonlyused.3Thisputs
thematriskofbeingundertreated;thus,thecurrent
recom-mendations are that one donotevaluatethe suitabilityof
radiotherapyonlytakinginto accountthepatient’sage, but
alsoassessinghis/herphysiologicalstatus,which hasbeen
increasinglybetterwiththeincreaseinmeanlifeexpectancy.9
The high toxicity of radiation therapy has stimulated
the use of moreconformational techniques, witha
three-dimensionalplanningthatallowsamoredirectedapproach,
such as modulated-intensity radiotherapy,26 which has
proventoreducemorbidityinsomestudies,particularlyin
theRadiationTherapyOncologyGroup(RTOG)0529study.36
Thistechniqueachievesinalesserdegreetheadjacentorgans
freeofneoplasia,asthebladder,rectum,smallintestine,
gen-itals,femoralhead,andperianalskin.9,26Withtheuseofthis
technique,onecanachieveafulldoseinashorterperiodof
time.9
Brachytherapy isa variantof conventional radiotherapy
but atan interstitial level, in which a high dose of
radia-tion,directlyincontactwiththeprimarytumor,isemitted,
notreachingthenormalsurroundingtissue,thecontralateral
mucosa,andthesphincter.9Inisolation,brachytherapyisnot
recommended,butthetechniquecanbeusedafteraresponse
tostandardchemoradiotherapy.9However,Falketal.in2014
publishedtheresultsofaclinicaltrial,inwhichtheseauthors
techniqueforspecificallytargetingtumorsandreducingthe
totaltimetotaloftreatment.37
Theacutetoxicityofradiationtherapyinvolvesprimarily
theskin, yieldingaradiation dermatitis,hematologic
com-plications,including myelosuppression; onthe other hand,
thepatientmayalsopresentwithfatigueandgastrointestinal
complications.9,26Thelong-termcomplicationscanbefibrosis
oftherectumandanalcanal,analsphincterdysfunction,skin
irritation,vaginalatrophy,anderectiledysfunction3,35;
radia-tionenterocolitiscanalsooccurandisasevere,howeverrare,
adversesideeffect.38
Sideeffectsandlong-termcomplicationsofradiotherapy
andchemotherapyhaveraisedthehypothesisofusing
alter-nativetreatments,suchassubmucosalendoscopicdissection,
restrictedtocarcinomasinsitu,andthathasproved
success-fulin similar squamouscarcinomas inthe esophagus and
pharynx.38
Metastaticdiseaseoccursin10–20%ofpatients,andthe
mostaffectedsitesaredistantlymphnodes,liver,andlung.29
The less affected sites are the peritoneum, bones, brain
andskin.29 The5-yearsurvivalforthesepatients,reported
in the literature, is 18–21%.29 The mean time to onset of
metastaticdiseasewas2yearsaftertreatmentforinsituanal
carcinoma.18
Duetothelowprevalenceofmetastasizedanalcarcinoma,
no clinical phase III clinical study was completed on the
treatmentofsquamouscellcarcinomaofthemetastasized
analcanal.26Currently,theonlyrecommendedtreatmentfor
patientswithdistantmetastasesorwithlocalrecurrenceunfit
forsurgeryischemotherapywithcisplatinand5-FU,duetothe
hematologicaltoxicityassociatedwiththeprolongeduseof
5-FUandMMC,9withaone-yearsurvivalrateof62.2%andwith
a5-yearsurvivalof32.2%,andmeansurvivalof34.5months.39
Cisplatinwasalsostudiedinpatientswithinsituanal
carci-nomainplaceofMMC,andshowedsimilarresults,andthat
drugcanbeconsideredforcombinationtherapywith5-FU,not
onlyincasesofmetastaticcarcinomaasincarcinomalocally
advanced.40
The treatment regimen consists of a continuous
infu-sionof5-FU 750mg/m2/day for5days,andanintravenous
dose 75mg/m2 of cisplatin on day one every 28 days.18,39
PhaseIIstudiescomparing5-FUandcisplatinwithcarboplatin
andpaclitaxelforthetreatmentofmetastaticsquamouscell
carcinomaoftheanalcanalareunderway,butwith
limita-tions,since5-FU/cisplatincombinationismostwidelyused,
whichmakesdifficultadirectcomparisonbetweenthetwo
combinations.18,26 Trialswithotherchemotherapeuticsthat
have proven effective in other squamous carcinomas are
also under way.39 The results reported by Kim et al.
sug-gestthatthe combination ofdocetaxel,cisplatin, and5-FU
canbebeneficialfortheremission oflong-termmetastatic
analcarcinoma,howeverthenumberofpatientsisagaina
restriction.41
Palliativesurgery andradiation should beconsidered in
the treatment of such patients.26 Eng et al. showed that
patients undergoing resection ofmetastases, notably liver,
obtainbetterresultsindisease-freetimeandmeansurvival,
whencompared withpatients not undergoingresection of
metastases.23However,thisprocedureisnotrecommended,
andmorestudiesareneededtoexploresurgicalcriteria.23
Squamous cell carcinoma of the anal canal, as well
as other squamous carcinomas in other sites, exhibits an
increased expression ofepidermal growth factor receptors
(EGFR),alsoknown asHER-1 andc-erB-1.26 Biological
ther-apytargetingthesereceptorshavebeenwidelydevelopedin
the treatmentofother squamouscarcinomas,andrecently
clinical trials have been conducted in order to evaluate
their effectivenessinlocally advancedand metastaticanal
carcinomata.23
Follow-up
There is controversy regarding the period of time that
mustelapsetoconsiderthatchemoradiotherapyhadfailed;
typically, 6 months should elapse for the occurrence of
tumorregression,but insomepatients, the periodmaybe
longer.23
Patientsincomplete remissionarereferredformagnetic
resonance imagingevery6monthsfor3years,asevidence
suggests that only<1%oftumorswill recurafter3years.9
Anoscopyishighlypainfulinthesepatientsundergoing
radi-ation therapy,sothisprocedureisnotrecommended.9 Any
suspiciouslesionshouldbebiopsied.9
Patientsundergoingabdominoperinealresectionforlackof
therapeuticresponseorrecurrenceshouldbereassessedevery
3–6monthsfor5years,withaclinicalevaluation.Additionally,
thesepatientsshouldperformachestandabdominalCTand
apelvicNMRannuallyfor3years.23
Immunodepressed patientsshould beevaluated every 4
weeks from the onset of treatment, in order to monitor
regressions.23
Prognosis
Poorprognosticfactorsforanalcancerincludemalegender,
positivelymphnodes(especiallyinguinalnodes),andprimary
tumor>5cm.9Skinulcerationwasalsoidentifiedinclinical
trialsasapoorprognosticfactorforlocalcontrolandmean
survival.9Baselinehemoglobinlevelswerealsopointedoutas
aprognosticfactorforpoorlocal-regionalcontrol,death,and
lowmeansurvival.9Smokerswithanalcarcinomaappearto
haveaworsemeansurvival,whencomparedtononsmoker
patients.9
Insquamouscarcinomasofthepharynxandlarynx,a
bet-terprognosiswasseen,whenHPVinfectionandmutationof
p16weredetected,withconsequentabnormalexpression.42
Meulendjiks et al. proved in their study that the presence
ofHPV infection and ofan alterationof p16expressionin
patients with squamous cell carcinoma of the anal canal
also provide a better prognosis, taking into account that
thesepatientsshowedbetterlocal-regionalcontrolandmean
survival.15
Studies related to serum antigenfrom squamous
carci-nomaestablishedacorrelationbetweenpretreatmentserum
levelsandclinicalclassificationofthetumor,nodular
involve-ment,responsetotherapy,riskofrecurrence,anddeath.Their
authorsconcludedthatelevatedserumlevelsofantigenwere
Discussion
Afterthissystematicreview,itappearsthatthereisstillmuch
tobeclarified,especiallyinthetreatmentarea.Despitea
ris-ingincidenceofanalcarcinoma,thelownumberofpatients
andthe exclusionofHIV-positivepatients inclinicaltrials,
inwhomthe prevalenceofthisdisease ishigher,havenot
allowedthecompletionofstudiesevaluatingnewtherapies.
Recently,somestudieshaveincludedpatientswithHIVin
clinicaltrials,23whichiscrucialsincethereismuch
contro-versyonthepossibleincreasedtoxicitywiththeuseofthe
standardtreatmentinthesepatients,inadditiontoallowing,
asalreadymentioned,alargersamplewithmoresignificant
andgeneralizableresults,sinceoneofthelimitationsofthose
studiesexcludingpatientswithHIVisthattheydonotallow
ageneralizationoftheirresultstothispopulation.Similarly,
womenshouldbeincludedinstudiesthattestreceptiveanal
intercourse as a risk factor, since most studies have only
reportedthis influenceinmen,excluding womenwiththe
samesexualbehavior.
Asstatedabove,areductionof80%ofanalcancerswith
the administration of the HPV vaccine occurs; it appears,
therefore,thatthenationalvaccinationplanshouldalsobe
extendedtomen.
Thetreatmentofbothlocalandmetastaticcarcinomahas
shownlittleprogressinthelasttwodecades,againthanks
totheshortageofthenumberofpatients;however,positive
resultsbegintoemergeinstudiestestingtherapiesthathave
provedeffectiveinother squamouscarcinomasfrom other
sites,notablybiologicaltherapy.
Thesuitabilityoftheindividualuseofradiotherapy,
tak-ing into account the individual prognostic factors (already
mentioned)andthebiologicalcharacteristicsofthetumor,is
apromisingstrategy.Inlinewiththis,moredirected
radia-tiontechniqueshaveevolvedandareofextremeimportance
inordertoreducethetoxicity,morbidity,andtheimpacton
qualityoflife.
Conclusion
Squamouscellcarcinomaoftheanalcanalisoneofthemost
prevalentmalignanciesinpatientswithHIV,whichisarisk
factorforHPVinfection,whichinturnisamajorcauseofanal
carcinoma.Receptiveanalsexisalsoanimportantriskfactor.
Somestudieshavebeenpublishedandcontinuetoemerge
inanattempttofindmoreeffectiveandalternativecytostatic
agents;however,wedonotcountonasufficientbodyof
evi-denceinordertoreplacetherecommendedcombinationof
5-FUandMMCinlocalizedcarcinomata,andof5-FUand
cis-platininmetastatictumors.23
Manystudiesareneededtopromoteprogressinthe
treat-mentofsquamouscellcarcinomaoftheanalcanal,aswellas
intheevaluationofthebiologicalcharacteristicsofthetumor
thatenableaprognosisoftheanswertotreatment,besidesan
individualandmoreeffectivetherapeuticsuitability.Onthe
otherhand,consideringthatthisneoplasiaisapreventable
diseaseinmostcases,inthefuture,onecancountonadvances
inprimaryandsecondarypreventionthroughvaccinationand
screening,respectively.
Conflicts
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interest
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