Npx Planning

7/31/2019 Npx Planning

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D R . U J J WA L C H A L I S ER E S I D E N T, N A M S , M D RT

Radiotherapy Planning inCa- Nasopharynx


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Further down, the mucosa overlies thepharyngobasilar fascia and the upper fibres of thesuperior constrictor, and behind these, the anteriorarch of the atlas. A lymphoid mass, the adenoid, liesin the mucosa of the upper part of the roof andposterior wall in the midline


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Each lateral wall receives the opening of thepharyngotympanic tube (Eustachian tube), situated10-12 mm behind and a little below the level of theposterior end of the inferior nasal concha .Posterior aspect of the orifice creats a protuberancecalled Torus Tubaris, posterior to it there is a variable depression in the lateral wall, the

pharyngeal recess (fossa of Rosenmller). It is theno.1 site for nasopharyngeal cancer.


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borders of nasopharynxant- posterior end of nasal septum and choanepost- clivus & C1-C2 vertebral bodies

superior- sphenoid bone/sinusinferior roof of soft palate


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epithelium anteriorly is ciliated, pseudostratifiedrespiratory in type.Posteriorly the respiratory epithelium changes to

non-keratinized stratified squamous epithelium which continues into the oropharynx andlaryngopharynx. The transitional zone between thetwo types of epithelium consists of columnar

epithelium with short microvilli instead of cilia.


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Pattern of spread

Inferiorly extend along the lateral pharyngeal walls andtonsillar pillars in almost one third of patients.Extension into the posterior nasal cavity is frequent butusually limited to less than 1 cm. Invasion of the

posterior ethmoids, the maxillary antrum, sphenoidsinus and the orbit occurs often.Spreads intracranially by routes of fissures andforamenas in the base of the skull and involve cranialnerves.Most important are foramen lacerum and foramen ovale which are in close proximity to the cavernous sinus andcranial nerve III to VI


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AJCC Staging

Tx T0 TisT1- Tumor confined to nasopharynx or extends tooropharynx and/or nasal cavity without

parapharyngeal extensionT2- tumor with parapharyngeal extensionT3- tumor involves bony structures of skull baseand/or paranasal sinusesT4-intracranial extension and/or involvement of cranial nerves, hypopharynx, orbit, or with extensionto infratemporal fossa/ masticator space


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Contd.


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Stage grouping

3yr OS by stage

I : 70-100%II : 65-100%III: 60-90%IV: 50-70%


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Three major pathways: 1 parapharyngeal group of lymph nodes (close proximity to cranial nerves IX toXII). Uppermost node is Node of Rouviere.

Jugular chain : Jugulo-digastric and Deep jugularnodes.Spinal accessory chain. Uppermost lies beneath thesternocleidomastoid muscle at the tip of the mastoid

process .


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Lymphatic drainage


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Nodaldistribution (Pamela Yude)

Retropharyngeal 80%

Level I -17%Level II 94%Level III-85%

Level IV- 19%Level V 63%


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cranial nerve involvementLee(n164) Chao

&Perez(n722)I - none noneII - 0.8 % 1.3III- 1.3% 3.5IV- 0.6 2.4 V - V13.5V25.8V33.9 7.8 VI- 5.1 13.3 VII- 0.1 3.6 VIII- --- 4.8IX-XII- 2.4 13.5


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WHO classification

Type I Keratinizing squamous-cell carcinomaType II Differentiated non- keratinizing carcinomaType III Undifferentiated carcinoma

95% cases are Type II and Type III


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Prognostic factors:

Stage at the diagnosis.Type III has better prognosisHigh EBV DNA level

EGFR over- expression AnemiaBetter prognosis in young age and female.


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Treatment

Surgical excision is not possible due to deep seatedlocation and close proximity to critical structures.Current recommendation :

Stage I-II definitive RT to npx +/-elective RT to neck

Stage III-IVB (+/- stage II b bulky) CCRT f/b

adj. chemo +/- neck dissectionfor residual neck nodes (NCCN)


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Metastatic :1. Cisplatin 5 FU as the first line.2. Others : Paclitaxel, Gemcitabine, Capecitabine as

single agents or in combination.3. If complete response Definitive RT to primary

and neck. (NCCN)


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Treatment preparation:

Set up supine with head extended, mask IMRT as far as possiblePlanning CT cover from skull vertex to 2 cm below

clavicles with 3mm slice thickness at gross tumorregionMRI + CT fusion for planning preffered for accuratedelineation of tumor targets and critical structures.Conventional 2D : mouth bite to minimize the doseto the oral cavity and mark wire enlarged nodes before simulation.


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Conventional set up :3 field lateral opposed for primary and upper neck,

matched to low neck field)

Conventional borders:superior- cover sphenoid sinus & base of skullinferior- match plane above true vocal cord

posterior- spinous processanterior- 2-3cm anterior to GTV, include posterior1/3 rd of maxillary sinus and pterygoid plates)


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Structures to be included in the volume:

In disease localised to thenasopharynx:1. entire nasopharynx

2. posterior 2cm of the

nasal cavity

3. posterior ethmoidalsinus

4. entire sphenoid sinusand basi-occiput bone

5. cavernous sinus

6. base of skull(toinclude foramen ovale,carotid canal and foramenspinosum7. pterygoid foss8. posterior 1/3 rd of maxillary sinus9. oropharyngeal wall tothe level of the midtonsillarfossa10. retropharyngealnodes, and11. neck nodes on bothsides


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IMRT

To reduce long term toxicities by reducing the dose tosalivary glands, temporal lobes, auditory structures andoptic structures. Volumes: GTV= gross diseaseCTV1 = GTV + microscopic infiltration and anatomicstructures at risk :entire nasopharynx, sphenoid sinus,cavernous sinus, base of skull, posterior1/2 nasal cavity,posterior 1/3 of maxillary sinuses, posterior ethmoidalsinus, pterygoid fossa, lateral and posterior pharyngeal walls to the level of the mid-tonsillar fossa, theretropharyngeal nodes and bilateral cervical nodesincluding level V and supraclav nodesCTV2 = low risk nodal regions

Example of guideline on anatomic structures/boundries for delineating


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Example of guideline on anatomic structures/boundries for delineatingclinical target volume (CTV) for IMRT at Pamela Youde Nethersole

Eastern Hospital

CTV 70 : GTV+ 5-10mm margin(2mm if nearneurological structures) and the whole nasopharynx

CTV60 : CTV70+ 5mm margin includes high risk localstructures including parapharyngeal spaces,posterior third of nasal cavities and maxillary sinus,pterygoid process, base of skull, lower half of sphenoid sinus, anterior half of clivus and lymphaticregions including bilateral RP nodes, level II, III and

VaCTV50 covers remaining levels IV to VbPTV : CTV + margin for setup variations(2mm)


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Conventional fractionation:

Primary and gross adenopathy : 70Gy ( @2Gy/#)Dose to the nodal area :

50 Gy for subclinical disease,60 Gy for < 3 cm node.70 Gy for > 3 cm node

Alt d F ti ti h d l


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Altered Fractionation schedules:

6#/week, accelerated during weeks 2-6. 70Gy to GTV and 50Gy to the subclinical disease.Concomitent boost accelerated RT: 72 Gy in 6weeks

@ 1.8 Gy/# larger field , 1.5 Gy boost as second daily fractions during last 12 treatment days.Hyperfractionation: 81.6 Gy in 7 weeks( 1.2Gy b.d.)


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Brachytherapy

Can be used for:BOOSTRECURRENT DISEASE

Types:1. Interstitial : AU- 198 grains, I 125 , Ir 192 wires.2. ICR : Ir 192 for HDR, Cs 137 for LDR


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Indication superficial tumor not more than 1 cmthick, not involving the underlying bone or deeply infiltrating the infratemporal space.

Contraindication Tumors extending into thenasal cavities or the oropharynx.


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Mould technique


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Rotterdam nasal applicator


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The dose is usually prescribed to an isodosecovering the surface of the underlying bone, whichis situated at 5 - 10 mm from the mucosal surface.

Low-dose-rate afterloading intracavitary implant 7 -12 Gy at 5 mm below the mucosa.High-dose-rate brachytherapy, with two 3 Gy fractions per day at 6 hour interval.

Total of fractions is 6 (after 60 Gy external beamirradiation) for T1 - 3 tumours, and 4 (after 70 Gy external beam irradiation) for T4 tumours.


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RCT Int 0099 n-147(Stage III-IV)RT vs CCRT Concurrent Cisplatin (3 cycles) + Adjuvant

Cisplatin + 5-FU (3 cycles).1. DFS :69 % vs. 24%.2. OS : 76% vs. 47%.3. Distant failure rate: 13% vs. 35%.4. Regional failure : 9% vs. 14%.5. Local failure: 10% vs. 33%.


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Wee in 2005 confirmed the results of Int 0099 with221 pts from Singapore with stage III-IV disease andsame protocol.

CCRT improved 2 yr OS 78 vs 85%, DFS 57 vs 75%DM 30 vs 13%Chan HK n-350 showed better results with CCRT

wkly Cisplatin 40mg/m2 OS 59 vs 70% PFS 52-60%

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