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General Principles of Target Delineation

  • The surgical approach (midfacial degloving, lateral rhinotomy, craniofacial, or endoscopic), can complicate the radiation field. If a craniofacial resection has been performed, the frontal graft should be included in the target volume. Fiducial markers implanted during surgery can help to delineate the tumor bed.

  • Preoperative CT and MRI should be evaluated to ensure that the initial tumor volume is covered in the high-risk CTV. Detailed description of the surgical procedure and pathology report is mandatory to properly define the CTV that should encompass all initial sites of disease and the subclinical tumor spread. MRI should be used in all cases to help delineation of the tumor unless medically contraindicated.

  • Adenoid cystic carcinomas are highly neurotrophic so radiotherapy volumes must encompass the afferent and efferent local nerves to the skull base. Esthesioneuroblastomas arise in the superior nasal cavity and in their early stages tend to invade the cribriform plate and anterior cranial fossa, and therefore, these regions should be encompassed in the target volume.

  • Lymph node metastases are unusual, so elective treatment of the neck is not mandatory but can be done at the discretion of the treating physician. However, elective neck irradiation should be considered for esthesioneuroblastoma; high-grade, high-stage squamous cell carcinoma, especially if originating from the maxillary sinus or there is invasion of the mucosa of the palate or of the nasopharynx; when there is involvement of the skin of the cheek or of the anterior nose; and invasion of the maxillary gingiva or the alveolus. Depending on the clinical situation (if tumor is well lateralized or if it crosses the midline), the lymph node levels Ib-IV can be covered (either unilaterally or bilaterally based on the clinical scenario).

  • Suggested target volumes at the gross disease and high- and low-risk regions are detailed in Tables 6.1 and 6.2 (Figs. 6.1 and 6.2).

    Table 6.1 Suggested target volumes for gross disease
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    Table 6.2 Suggested target volumes at the high- and low-risk subclinical regions
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    Fig. 6.1
    figure 1

    An example of a 91-year-old patient with a cT4aN0 squamous cell carcinoma of the ­maxillary sinus. Patient refused surgery and was treated with definitive chemoradiation. The GTV is noted in the green color while the high-risk subclinical CTV is noted in the red color. Only the ipsilateral neck was included in the pink color given the lateralized right maxillary sinus location as well as the patient’s advanced age

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    Fig. 6.2
    figure 2

    An example of a 43-year-old patient with a pT4aN0 squamous cell carcinoma of the ethmoid sinus. Patient is s/p ethmoidectomy, sphenoidectomy, nasal exenteration, and anterior craniotomy. Patient then received adjuvant chemoradiation. The CTV is noted in the pink color. As this was a low-grade tumor with no neck involvement, no LN regions were treated

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