Paranasal sinus melanoma – definitive stereotactic body radiation therapy
Skull Base Region
Paranasal Sinuses
Histopathology
Mucosal Melanoma
Prior Surgical Resection
Biopsy and transnasal debulking
Pertinent Laboratory Findings
BRAF negative
Case description
A 67-year-old female presented with a history of rhinosinusitis over several months. On physical examination, a mass occupying the right nasal cavity was noted, with associated right eye proptosis. Magnetic resonance imaging (MRI) demonstrated a mass in the right sinonasal cavity extending towards the right orbit ( Figure 2.10.1 ). Biopsy and debulking of the mass demonstrated a mucosal melanoma. Staging with a positron emission tomography/computed tomography (PET/CT) scan demonstrated the known primary mass in the right sinonasal cavity as well as a solitary metastasis involving the T1 vertebra. The patient then underwent stereotactic body radiation therapy (SBRT) ( Figure 2.10.2 ).
Radiosurgery Machine
Varian Edge
Radiosurgery Dose (Gy)
40 (with elective 30 Gy volume), at the 75% isodose line
Number of Fractions
5
Figure 2.10.1.
Axial and coronal postcontrast T1-weighted images demonstrate a heterogeneous enhancing mass arising from the right nasal cavity and involving the entire ethmoid sinus. There is extension into the right maxillary sinus and protrusion into the right orbit causing anterolateral displacement of the right medial and inferior rectus muscles. There is elevation of the right cribriform plate secondary to the mass expansion in the ethmoid sinus. There is an additional heterogeneous enhancing mass in the left maxillary sinus.
Figure 2.10.2.
Axial, sagittal, and coronal CT simulation images. The 40 Gy gross total volume (GTV) is outlined in red, 40 Gy planning target volume (PTV) is outlined in green , and elective 30 Gy PTV is outlined in blue .
Critical Structure
Dose Tolerance
Globe
Max point (0.03 cc) <30 Gy
0.1 cc <25 Gy
Optic nerve
Max point (0.03 cc) <25 Gy
0.2 cc <23 Gy
Brainstem
Max point (0.03 cc) <31 Gy
0.5 cc <23 Gy
Spinal Cord
Max point (0.03 cc) <28 Gy
0.35 cc <22 Gy
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