Evolution of Care of Orbital Tumors with Radiation Therapy

Abstract

Orbital tumors are rare lesions comprising 0.1% of all tumors and less than 20% of all ocular diseases. These lesions in children and adults differ significantly in their incidence, tumor type, and treatment management. Although surgery and systemic therapies are commonly used in the management of these diseases, radiation therapy has become a widely used treatment for both benign and malignant tumors of the orbit. Radiotherapy is used as a definitive treatment to provide local control while avoiding morbidity associated with surgery for some tumors while it is used as an adjuvant treatment following surgical resection for others. For many tumors, radiation provides excellent tumor control with preservation of visual function. This article is dedicated for presenting the most common applications of orbital radiotherapy. A brief overview of the commonly available radiation therapy modalities is given. Dose constraint goals are reviewed and acute and long-term side effects are discussed. Orbital tumors covered in this article include optic glioma, ocular melanoma, retinoblastoma, orbital rhabdomyosarcoma, orbital lymphoma, and lacrimal gland tumors. Background information, indications for radiotherapy, and goals of treatment for each case example are described.

Keywords: IMRT; carbon-ion; carcinoma; glioma; lymphoma; melanoma; proton therapy; radiation; retinoblastoma; sarcoma.

Fig. 1

Proton radiotherapy plan in a 33-year-old male with left orbital tumor, treated with double-scattering proton beam to a total dose of 54.0 Gy (RBE)/30 fractions.

Fig. 2

Axial slice from a planning CT. The lens is shown as well as the retina (RET) and its fovea (FOV). The retina contour, more easily seen in the CT than in the MR scan, includes the retina, the choroid, and the sclera. The fovea is indicated just lateral to the optic disk, the region where the optic nerve (OPT N) exits the globe. (Figure is provided courtesy of Dr. Barbara Fullerton.)

Fig. 3

This image shows retinas (RET) and the optic nerves (OPT N). The optic tracts (OPT TR) extend posteriorly from the chiasm. The hypothalamus (HYPOTH) is located on either side of the third ventricle. The anterior temporal lobes are shown in the most lateral portion of the brain. (Figure is provided courtesy of Dr. Barbara Fullerton.)

Fig. 4

This image shows the optic nerves (OPT N) extending through the optic canal medial to the anterior clinoid processes to join the chiasm. The optic tracts (OPT TR) extend posteriorly from the chiasm to the lateral geniculate nucleus of the thalamus. The hypothalamus is wider at this level than in Fig. 3 . The third ventricle is located at the center of the hypothalamus. (Figure is provided courtesy of Dr. Barbara Fullerton.)

Fig. 5

MRI image of a progressive optic pathway glioma causing significant proptosis in a 19-year-old patient.

Fig. 6

Pencil beam scanning for optic glioma. A 13-year-old female patient with right optic pathway glioma treated with proton radiation therapy to a total dose of 50.4 Gy (RBE)/28 fractions. The prechiasmatic location of the tumor and its small size made it anatomically very amenable to proton radiation therapy with excellent sparing of nearby normal tissue.

Fig. 7

Treatment of iridociliary melanoma: ( a ) the beam's eye view of the model shows the structures of the globe, projection of the target for the selected gaze direction, and the beam aperture including a 2– to 3-mm margin; ( b ) the field is set up based on the light projection through the beam aperture, without fiducial markers; ( c ) the planned dose distribution on the surface of the cornea and sclera, in polar view; and ( d ) the surface dose distribution overlaid on the photo of the cornea. (Figure is provided courtesy of Dr. Alexei Trofimov.)

Fig. 8

The polar projection of the eye fundus overlaid with ( a ) a mosaic of narrow-angle photos, and ( b ) wide-angle photo. The target is defined based on the position of four fiducial markers, with the aid of fundus photos. (Figure is provided courtesy of Dr. Alexei Trofimov.)

Fig. 9

Treatment of choroidal melanoma: ( a ) the beam's eye view of the model shows the structures of the globe, projection of the target for the selected gaze direction, the beam aperture including a 3-mm margin, and location of four fiducial markers (tantalum rings); ( b ) the dose distribution is shown on the polar projection of the fundus, overlaid with the photo-mosaic. (Figure is provided courtesy of Dr. Alexei Trofimov.)

Fig. 10

A cross-section of the eye model shows the position of the target and structures of the globe for the selected gaze direction: ( a ) the required range and modulation width of the spread-out Bragg peak are determined based on the target depth and dimensions, with added anterior and posterior margins of 3–4 mm; ( b ) the corresponding sagittal dose distribution. (Figure is provided courtesy of Dr. Alexei Trofimov.)

Fig. 11

Volumetric modulated arc therapy plan for right conjunctival MALT lymphoma treated with conventional radiation therapy to a total dose of 24 Gy/12 fractions.

Fig. 12

A child with leukocoria due to retinoblastoma of the left side.

Fig. 13

Representative proton radiotherapy plan in a patient with bilateral disease. Clinical target volume is confined to the tumor in the posterior retina. Protons provide excellent sparing of tissues outside the target area.

Fig. 14

Passive-scattering proton therapy for orbital rhabdomyosarcoma. A 9-year-old female with embryonal RMS of right orbit, group III, stage I, s/p resection biopsy of the mass and VAC chemotherapy per protocol ARST0331 followed by adjuvant proton radiation to a total dose of 45 Gy (RBE)/27 fractions with cone down to 48.8 Gy (RBE) to gross residual disease.

Fig. 15

Composite proton radiotherapy plan for adenoid cystic carcinoma (ACC) of lacrimal gland. A 12-year-old patient with ACC, cribriform type, of right lacrimal gland, s/p pre-op RT to a total dose of 20 Gy (RBE)/10 fractions, en block resection of the tumor followed by post-op RT to a total dose of 54 Gy (RBE)/30 fractions. The accumulative dose to the tumor bed is 74 Gy (RBE). The fifth nerve is tracked and a dose of 54 Gy (RBE) was prescribed.