NASAL CAVITY AND ETHMOID AIR CELLS

ANATOMY

MAXILLOTOMY
Ethmoid sinuses
  • comprise several small cavities, called ethmoid air cells,
  • located within the ethmoidal labyrinth located below the anterior cranial fossa
  • is between the nasal cavity and the orbit.

Drainage of Ethmoid Sinuses

  • Middle ethmoidal cells open directly into the middle meatus
  • Anterior cells drain indirectly into the middle meatus via the infundibulum.
  • Posterior cells open directly into the superior meatus

STAGING

  • There was no official AJCC unti sixth edition.

UF and the T-classification is approximated as follows

  • Stage I: confined to site of origin
  • Stage II: extension to adjacent sites (ie.paranasal sinuses, skin, orbit, pterygomaxillary fossa, and nasopharynx equivalent to T3 and small T4.)
  • Stage III: base of skull or pterygoid plate destruction: intracranial extension.

PROGNOSIS

  • prognosis of patients with nasal cavity is better than maxillary sinus (66% vs 45% OS)

GENERAL TREATMENT

STAGE I

GENERAL

  • Radiotherapy and surgery are effective
    • Primary surgery is generally favored to reduce unilateral or bilateral optic nerve injury.
    • Radiotherapy may be electrons (tumors < 5 cm deep) or IMRT (3D)

ANTERIOR NASAL SEPTUM

  • Interstitial brachytherapy is an excellent treatment option for small anteroinferior septal lesions (1.5) to avoid partial removal of the anterior nasal septum.

POSTERIOR NASAL SEPTUM

  • Posterior nasal septum lesions are generally treated by surgery.

STAGE II AND OPERABLE STAGE III

  • surgery is the best
  • postoperative irradiation is indicated in most cases.

TARGET VOLUMES FOR SINONASAL CANCERS (IMRT)

SMALL ANTEROINFERIOR SEPTAL LESIONS

  • brachytherapy by a single-plane implant
  • 2-cm margin around the lesion
  • no elective neck irradiation even for large tumors.

PRIMARY RADIATION THERAPY

GTV prechemotherapy volume 66-70 Gy
CTV1 GTV + 1.0-1.5 cm 66-70 Gy
CTV2 CTV1 + 1.0 1.5 cm 59-63
CTV3 nodal volumes, nerve tract and bose of skull margin 54-57 Gy

POSTOPERATIVE RADIOTHERAPY

Boost positive margins and gross residual 66-70 Gy
CTV1 Primary tumor bed + 1.0-1.5 cm 60 Gy
CTV2 Surgical bed 57 Gy
CTV3 Trigeminal nerve if there is perineural invasion
additional skull base margin
elective nodal volume if indicated
54 Gy

EXAMPLE POSTOPERATIVE CTV VOLUMES

OLFACTORY REGION TUMOR

  • CTV2 should include the cribriform plate

ETHMOID AIR CELLS

ADJUVANT (POSTOPERATIVE RADIOTHERAPY)

  • BOOST subvolumes of CTV1
    • positive margins
    • gross residual
  • CTV1
    • includes primary tumor bed with 1.0 to 1.5 cm margin.
  • CTV2 (surgical bed)
    • frontal sinus
    • maxillary sinus
    • sphenoid sinus
    • bony orbit if orbital exenteration performed.
    • cribriform
  • CTV3
    • encompass the tract of V2 to the foramen rotundum, if there is perineural invasion.
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