84 y/o M with high-grade cutaneous squamous cell carcinoma s/p Mohs resection with extensive large caliber perineurial invasion and positive surgical margins.


TECHNIQUE: Postoperative radiation using VMAT.
DOSE: The low-risk PTV (PTV50), encompassing the postoperative tumor bed and the antegrade and retrograde course of the bilateral CN V1 nerves received 50 Gy in 25 fractions. The high-risk PTV (PTV66) sequentially boosted the tumor bed with 16 Gy in 8 fractions for a cumulative dose of 66 Gy in 33 fractions. 
  • Tumor bed/skin graft and an additional margin were wired to represent the high-risk CTV and covered with 1 cm of bolus
  • The supraorbital notches (sites of supraorbital foramina) were palpated and marked with BB’s
  • Patient was immobilized in a short thermoplastic head-mask
Case contributed by Duke University

  • CTV66: post-op tumor bed with margin given infiltrative, high-grade histology with positive margins. 
  • CTV50: CTV66 + post-op tumor bed + course of bilateral supraorbital nerves due to midline tumor location. 
  • PTV: CTV + 3-5mm.
  • Retina, macula, lens, globe, optic nerve, lacrimal gland, and brain.
  • Contouring the macula as a separate OAR may facilitate sparing of central vision if the retina cannot be fully spared. The macula is the portion of the retina immediately lateral to the optic nerve. 
Additional Notes:
  • Elective nodal irradiation not administered to reduce morbidity given that nodes were clinically and radiographically negative. ENI would have been necessary bilaterally given the midline location of the primary tumor.
  • Consider treating with en face electrons if the tumor or resection bed is flat and adequate PTV coverage may be achieved.
  • Pre-treatment MRI performed to rule out gross supraorbital nerve/CN V1 involvement and to directly visualize V1 and fused to CT-simulation scan. If grossly involved, consider boosting CN V1 to 60-66Gy up to the supraorbital foramen.
  • If utilizing an SIB technique then the low-risk PTV may be treated to 54-56 Gy and the high-risk PTV to 63Gy in 30 fractions. 

  • For detailed cranial nerve contouring guidelines and CTV design in head and neck cancers, see Ko et al. PRO 2014, Biau et al.  Radiother Oncol 2019, and Bakst et al. IJROBP 2019. Consultation with a neuroradiologist is desirable whenever possible.
  • CN V1, the ophthalmic division of the trigeminal nerve, is the major nerve at risk in this region. It transmits sensory fibers (including the supraorbital nerve) from the upper face/forehead, orbit, skull, and eye.
  • Path of V1: The supraorbital nerve enters the orbit via the supraorbital foramen and parallels the path of the superior rectus muscle. It terminates at the orbital apex at the superior orbital fissure and joins V2 and V3 at the trigeminal ganglion in the cavernous sinus in the middle cranial fossa.
  • If there is evidence of clinical/gross involvement then contour CN V further proximally along the cavernous sinus, through Meckel’s cave, and ultimately the cisternal pons.
  • For clinically apparent PNI consider anterograde nerve coverage as well. 
  • The temporal branch of CN VII is also at risk in forehead SCC with PNI. The temporal branch innervates the frontalis and orbicularis oculi muscles. This was covered by the CTV50 although it was not traced through the parotid to the main trunk of CN VII.