Parotid cancers,anatomy, pathology, management and radiotherapy target volume contouring

1. Malignant Parotid Gland Tumours :
Radiotherapy Perspective
Dr. Gaurav Kumar
Senior Resident
Dept. of Radiotherapy
SGPGI, Lucknow

33. Workup
1) History & Physical Examination ( Special emphasis on fixity of mass,
neck nodes, facial nerve examination, trismus )
2) Additional : Mirror and fibreoptic examination
3) CT/MRI of Face & Neck
4) Chest X-Ray (CT Thorax as clinically indicated)
5) FNA Biopsy
6) Routine Blood Parameters
7) Pure tone audiometry ( Additional)

34. Treatment Algorithm
T1 & T2 (N0) Parotidectomy with complete resection
of tumor (Neck dissection for high grade
tumors)
T1 & T2 (N+) Parotidectomy + Neck Dissection
T3/T4/N+ Parotidectomy + Neck Dissection

35. Indications of Post operative Radiotherapy
1) T3/T4 tumors
and/or
2) Incomplete or Close resection margin
3) High grade histology
4) Recurrent disease
5) Peri neural disease
6) Node + disease

36. Defining Parotid Bed:
• The parotid gland extends from the zygomatic arch superiorly to beyond the lower
border of the mandible inferiorly .
• Posteriorly, the gland dips in the space between the mandible and the mastoid, with
the adjoining external auditory meatus intimately surrounded by the gland in its free
borders, that is, anteriorly and inferiorly.
• On a deeper plane, the parotid is related to the styloid process and the muscles
connected to it.
Locoregional involvement :
Local infiltration of tissues adjacent to the parotid gland is the main pattern of spread.
This follows the anatomical borders of the parotid gland and in cases of perineural
invasion, the facial nerve to the stylomastoid foramina.

38. • Soft tissue extension – The parotid gland, along with periparotid lymph
nodes, facial nerve and vessels lie within the parotid facial compartment – The fascia
is deficient in the medial aspect, thus an increased risk of spread to the
parapharyngeal space.

39. • At risk areas: – Infratemporal fossa – Parapharyngeal space –
Masseter – Diagastric – Skin
• Bone infiltration - at risk areas include: – Lateral part of the floor of middle
cranial fossa – Neck of mandible – External auditory meatus – Inferior surface of
styloid process.

40. CLINICAL TARGET VOLUME DEFINITION
(ICRU 50 & 62)

41. CLINICAL TARGET VOLUME SELECTION
Position: Supine with arms by the side (use shoulder retraction)
Immobilisation: Thermoplastic head and neck cast with head rest
Planning CT Scan: 3mm slide (vertex to carina)

42. Superiorly: CT Slice passing through most lateral and
superior extent of zygomatic arch (i.e. above TM Joint)
Posteriorly: Posterior most attachment of pinna.
Laterally: Skin
Anteriorly: Posterior half of masseter.
Medially: Infratemporal fossa and soft tissue plane in front
of base of skull.

44. Anteriorly: Follows anterior border of masseter.
Medially: Parapharyngeal space and lateral pterygoid plate
Posteriorly: Include lateral retropharyngeal, soft tissue
anterior to skull base and to include external auditary canal.
Laterally: Skin

46. Below the level of external auditory canal/level of
mastoid air cells
Anteriorly: Anterior border of masseter
Medially: Include Parapharyngeal space and lateral retropharyngeal
nodes
Posteriorly: Posterior border of mastoid process (posterior extent of
mastoid air cells) and soft tissueplane anterior to skull base
Laterally: Skin

48. Level of angle of mandible :
Anteriorly: Anterior to the submandibular gland and includes level Ib
nodal volume
Medially: Medial border of level Ib and Submandibular gland, to include
parapharyngeal space
Posteriorly: To include level IIa and IIb nodal volumes
Laterally: Skin

50. Inferior level : Superior cornu of hyoid bone
Anteriorly : To include submandibular gland
Medially : Medial border of level Ib and Submandibular gland, to
include parapharyngeal space
Posteriorly: To include nodal outlining of level IIb (following back
to the sternocleidomastoid muscle)
Laterally: Skin

52. When to apply skin bolus :
Skin involvement
• Poor prognostic indicator to develop distant metastasis
• Relatively low incidence for local recurrence
In order to obtain adequate skin dose, TMG recommends bolus in
following situation:
1) Skin involvement
2) Close superficial margin
3) Tumor spillage/Capsular rupture

53. General points :
• The margins described adapted to include any bone infiltration
• The mandibular ramus is included in clinical target volume
• Any air cavity is excluded from the clinical target volume
Planning target volume:
• Varies according to institution
• Depends upon geometric accuracy of immobilisation system
• PTV1 : Planning target volume to be treated to radical (in case of
inoperable disease)or postperative dose
• PTV2 : Planning target volume to be treated to an elective dose

55. Elective neck irradiation : (Neck not addressed by
surgery)
To include level Ib-IV
TMG Consensus for elective nodal irradiation
1) High grade histolgy
2) T3/T4 disease
3) Histology:
Squamous cell carcinoma
Adenocarcinoma
Undifferentiated carcinoma
High grade mucoepidermoid carcinoma
Salivary duct carcinoma

56. Post-operative neck irradiation :
1) Multiple nodes
2) > 2 nodal levels involved
3) Extracapsular spread +
4) N3 node
Outlining Organs at Risk :
• Both cochlea (with 3mm PRV)
• Contralateral Parotid
• Spinal Cord (with 3mm PRV)
• Brainstem
• Lens

57. Trial Management Group Recommendations :
1) Ipsilateral node group Ib-V are contoured and defined at risk nodal volumes
2) Ib, IIa, IIb commonly lie within surgical bed hence receive 60 Gy/30# dose
3) Patient without neck dissection, level III,IV,V are included in CTV2 (50 Gy/25#
conventional or 54 Gy/30# in IMRT)in following situations
• T3/T4
• All High Grade tumours
• Histological subtypes
Squamous cell carcinoma
Adenocarcinoma
Undifferentiated carcinoma
High grade mucoepidermoid
Salivary duct carcinoma

58. Trial Management Group Recommendations Continued:
4) Post-operative nodal irradiation recommended in:
• Extracapsular spread
• N2b disease
• N3 status

59. Take Home Messages :
1) All T3/T4 should undergo Ipsilateral neck dissection (SOHND or preferably
MRND)
2) T1/T2 N0 with favourable histology and low grade tumours can be spared
of neck dissection and Primary & Neck node irradiation.
3) Ipsilateral level Ib,IIa,IIb nodes are always included in CTV1 (60Gy/30#)
4) If neck not addressed with surgery then it should be addressed during RT
(even in case of cN0 status) in case of high grade tumours, T3/T4 disease and
unfavourable histologies.
5) Recurrent tumours even if T1/T2 must receive PORT.
6) No role of concurrent chemotherapy till date (even in ECE).
7) Facial Nerve preservation in surgery and Cochlear sparing in Radiotherapy
remains the state of art.

61. Thank You