Radiation Oncology: A Question-Based Review

Orbital Pseudotumor

John P. Christodouleas and Roland Engel

image Background

What are 2 other terms for orbital pseudotumor (OP)?

Other terms for OP:

1.     Lymphoid hyperplasia

2.     Pseudolymphoma

What is the eponym given to OP with cavernous sinus involvement?

Tolosa-Hunt syndrome is OP with cavernous sinus involvement.

What % of pts with OP will subsequently develop a malignant lymphoma?

5%–25% will subsequently develop a malignant lymphoma. (Orcutt JC et al., Br J Ophthalmol 1983; Mittal BB et al., Radiology 1986)

Does OP affect children, adults, or both?

OP affects both children and adults. ~5%–15% are pediatric cases. (Smitt MC et al., Semin Radiat Oncol 1999)

Name 5 signs/Sx associated with OP.

Signs/Sx associated with OP:

1.     Orbital mass

2.     Orbital pain

3.     Proptosis

4.     Abnl extraocular movements (e.g., diplopia)

5.     Decreased visual acuity

image Workup/Staging

What is the DDx for an orbital mass?

Rhabdomyosarcoma, OP, malignant orbital lymphoma, thyroid ophthalmopathy, and nodular fasciitis

What is the workup for an orbital mass?

The workup is the same as for a suspected lymphoma, including CT/MRI brain/orbit.

Is there a formal staging system for OP?

No. There is no formal staging system for OP.

image Treatment/Prognosis

What is the initial Tx for OP?

Steroids are the mainstay initial Tx for OP. (Smitt MC et al., Semin Radiat Oncol 1999)

What are the response rate and long-term control rate with a single steroid course?

1.     Response rate: 80%

2.     Long-term control rate: 33%

(Mombaerts I et al., Ophthalmology 1996)

What is the 2nd-line therapy for OP?

RT is the 2nd-line therapy for OP.

What is the most common RT dose/fx schedule for OP?

20 Gy in 10 fx is the most commonly employed schedule for OP.

What are the estimated control rates for OP with RT?

Control rates with RT range from 66%–100%. (Smitt MC et al., Semin Radiat Oncol 1999)

What is the standard RT setup for OP?

There is no standard RT setup, as the process may involve any aspect of the orbit. Tx must be individualized.

Can RT be repeated for OP?

Yes. RT can be repeated, if necessary.

image Toxicity

What are the late side effects of orbital RT?

Cataracts, permanent eye dryness, retinopathy, and optic neuropathy

What is the RT dose limit of the lens?

Try to limit the lens to <8–10 Gy depending on the clinical situation.

Diabetic pts are at an increased risk for what complication after orbital RT?

After orbital RT, diabetic pts are at an increased risk for RT retinopathy. (Wakelkamp IM et al., Ophthalmology 2004)