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20 Cards in this Set

  • Front
  • Back

Anatomy

  • The nasal part of the pharynx.
  • Pyramid shape
  • Lateral walls = orifices leading to eustachian tubes

Borders

  • Sup: base of skull
  • Inf: upper border of soft palate
  • Ant: nasal cavity 
  • Post: upper cervical vertebrae

Lymphatics

  • Retropharyngeal
  • Deep & Post Cervical
  • Supraclavicular 

Epidemiology

  • Relatively uncommon
  • High prevalence in Southern Chinese - rice powder. link with environment and customs rather than genetics
  • 50-70years
  • M:F 3:1
  • Antibodies from Epstein-Barr strongly associated

Aetiology

  • Environmental factors - common amongst Asian
  • Epstein-Barr Virus
  • Alcohol
  • Smoking 

Spread

  • Superiorly: via foramen lacerum to involve cranial nn (2-6), base of skull
  • Inferiorly: Into oropharyngeal wall & soft palate
  • Anteriorly: Into nasal cavity & paranasal sinuses
  • Posteriorly: Into prevertebral mm causing pain w/ head movement
  • Laterally: eustachian tubes

Symptoms

  • Nasal: bloody discharge, obstructed nostrils, difficulty breathing
  • Ears: conductive deafness, otitis media, blocked ears
  • Neurological: extension of ca thru foramen lacerum - effecting cranial nn.

Diagnosis

  • Nasopharyngoscopy
  • Indirect laryngoscopy
  • Biopsy
  • Blood test - Epstein Barr antibodies
  • CT / MRI
  • Chest x ray
  • Liver US
  • Bone scan

Staging T

  • T1: confined to nasopharynx
  • T2: extends to soft tissue of osopharynx &/or paranasal sinus
  • T2a: without parapharyngeal extension
  • T2b: with parapharyngeal extension
  • T3: tumor invades body structures &/or paranasal sinuses
  • T4: intracranial extension &/or involvement of cranial nn, orbit

Staging N

  • N1:  single, ipsilateral node
  • N2a: single ipsilateral node 3-6cm
  • N2b: multiple ipsilateral nodes <6cm
  • N2c: bilateral or contralateral nodes <6cm
  • N3: >6cm

Surgery

  • Debulk the primary. 
  • Difficult site to access
  • Neck dissection to remove +ve nodes

Radiation Therapy

  • Primary modality
  • Radical doses
  • Multiphase
  • EBRT v Brachy
  • Chemo combined = advantage

Patient Set Up

  • Mouth bite = push tongue down
  • Cervical vertebra parallel to couch top

CT Sim

  • Slice: 2-3mm
  • Range: beyond orbits & to encompass primary site >> 5cm INF SSN

Isocentr Location

  • Isocentre = junction 
  • Typically @ thyroid notch. Avoid thru tumor or nodes

Field Arrangement

  • Lateral Opposing = cover primary lesion and upper cervical lymph nodes
  • Anterior = lower neck and supraclav fossa

Standard Field Borders

  • Sup: primary / base of skull / known spread
  • Ant: primary / upper neck nodal chains
  • Post: post cervical nodes
  • Inf: inf as possible / post cervical nodes / palpable masses
  • Shielding: brain, orbits, nasal cavity, mouth

Phase 1a

  • Primary + post cervical nodes: high dose ~50GY
  • Large opposed laterals
  • SCord lies within fields - dose constraint 45Gy

Phase 1b

  • To conform dose, Phase1 laterals split into anterior photon beam + posterior electron beam
  • if patient position w/ SCord parallel to couch top, a straight ant/post junction not possible.
  • If not, blocking required to shape each field to junction on skin
  • Appropriate electron E = boost dose to post cervical nodes, sparing underlying Scord 9-12MeV

Prescription

  • Phase 1: 50Gy/25#
  • Phase 2 Boost: 16Gy/8-10#