Primary iris tumors are relatively uncommon and are, readily discernible through multimodality examination, (see Chapter 4). Of these, most are benign, occult, iridociliary, cysts.1,2 Anterior segment malignancies are most, commonly iris melanomas, followed by ciliary body, neoplasia that invade the iris and/or anterior segment.3,4, Most commonly occurring in Caucasian patients, these, brown or tapioca-colored malignancies commonly contrast, with their underlying lightly pigmented iris stoma.5,6, However, when pigmented iris melanomas arise within, dark irides, additional findings may be needed to establish, a clinical diagnosis., Iris tumors can be broadly classified as cystic or solid,, discernible through slit-lamp examination, transillumination,, and gonioscopy (Mind map 23-1). However,, advanced imaging techniques such as high-frequency, UBM and/or anterior segment optical coherence, tomography (AS-OCT) are the most valuable tools in, confirming and differentiating these characteristics (see, Chapter 3). Herein, we offer our clinical approach, delve, into their classification, and highlight the specialized, imaging techniques utilized for their differentiation.
Chapter Keyword: iris
Treatment of Iris Tumors
Iris neoplasms include nevi, melanocytomas, melanomas,, hamartomas (e.g., Lisch nodules), as well as cysts of the, iris stroma and pigment epithelium. Amelanotic tumors, are more likely vascular, epithelial, or metastatic.1,2 Most, can be distinguished by clinical examination, including, slit lamp, gonioscopic, ultrasound, optical coherence, tomography (OCT), and angiographic techniques.3, However, diagnosing small indeterminate lesions can be, difficult. They may require photographic documentation, for growth over several weeks, months, or even years as, well as for biopsy (see Chapter 5)., It is important to determine the entire anatomic extent, of the tumor, as tissue invasion and displacement can, help determine if a tumor is benign or malignant. For, example, this is particularly important for iris melanoma, extending into the ciliary body or a primary ciliary body, tumor extending into or through the iris root. For this, reason, slit-lamp imaging, gonio-photography, UBM,, and anterior segment OCT imaging as well as fluorescein, angiography (FA) help this determination. The usefulness, of CT and MRI has been described but is less helpful, in discriminating between different types of iris tumors.4, Treatments for any individual tumor depend highly on the, clinical or biopsy-proven diagnosis, size, and extent. Benign, lesions (e.g., nevi and small cysts) are typically observed, and may not require treatment. Because of their anterior, and clearly visible location, iris tumors—especially iris, melanomas—are treated when relatively small compared, to more posteriorly located uveal melanoma, yielding, more favorable prognoses. Treatment modalities typically, include surgical excision (sector iridectomy), radiation (e.g.,, charged particle, plaque brachytherapy), and enucleation.5-7
Diagnosis of Choroidal and Ciliary Body Melanoma
Extending from the optic disc to the pupillary margin,, the vascular uvea contains melanocytes that can transform, into what is the most common primary intraocular, malignancy in adults, uveal melanoma (UM).1-3 Further,, the uveal layer can be anterior to posteriorly divided into, iris, ciliary body, and choroidal portions. COMS examined, choroidal melanomas and found their average, presenting age to be 60 years; however, uveal melanomas, can occur as early as infancy.1,4,5, Younger patients with choroidal melanoma tend to, have a better prognosis, and it’s thought due to a better, immunological profile.1-3,6 UM incidence is nearly equally, distributed between males and females.1,7 The most common, location of the tumor is the choroid (85%–90%),, followed by the ciliary body (5%–8%) and iris (3%–, 5%).1,2 The annual age-adjusted incidence per million, population is 6.02 for non-Hispanic whites, 1.67 for Hispanics,, 0.38 for Asians, and 0.31 for blacks.8, UMs may arise de novo or from pre-existing uveal nevi., They are also more common in patients with outdoor, occupations, beneath Australia’s ozone hole, on the, sun-exposed lower half of the iris, and in arc welders., This suggests ultraviolet light exposure is a predisposing, factor. However, the etiologic risks of ultraviolet, light exposure have been disputed.9 In addition, several, geographical clusters of UM (primarily affecting, young patients) have been discovered with no identifiable, genetic or environmental factors (e.g., Huntersville,, NC, USA and Auburn, AL, USA).10, UM is not hereditary; however, there have been reports, of familial cases affecting several family members.11, Melanoma is typically a unilateral, unifocal disease, but, cases of primary bilateral or multifocal tumors have been, published.12,13 BAP1 tumor predisposition syndrome has, been associated with an increased risk of developing UM, (2.8% incidence) compared to 0.0061% in the general, population.14,15 Like most cancers, the development of, UM is likely multifactorial.
High-Dose Rate Brachytherapy for Ocular Tumors and Benign Growths
Brachytherapy has long been used to treat benign and, malignant ocular tumors as well as neovascular and fibrovascular, growths.1-24 Widespread acceptance of eye- and, vision-sparing plaque brachytherapy started with lowdose, rate (LDR) cobalt-60 eye plaques.1 Later, LDR, iodine-125 (125I) and then LDR palladium-103 (103Pd), seeds were affixed within high-Z gold, shielded plaque, seed carriers, and thus blocked the radiation posterior, and to the sides of the plaque (Table 21-1).25-28 Iodine-125, and 103Pd plaque brachytherapy diminished radiation, exposure to clinicians, improved the intraocular radiation, distribution, and allowed for outpatient, continuous,, multiday treatments (Mind Map 21-1).24, LDR ruthenium-106/rhodium-106 (106Ru/106Rh) and, high-dose rate (HDR) strontium-90/yttrium-90, (90Sr/90Y) beta-emitting radiation devices were commercialized, in England, Germany, and Russia.21,29-35 Of, these, Amersham’s legacy SIAQ 7321 (Amersham Corporation,, Amersham, UK) and Resutech (Moscow, Russia), HDR 90Sr/90Y sources are most like the currently available, LV Y-90 Disc (Liberty Vision Corp., Portsmouth,, NH, USA). However, unlike those prior 90Sr/90Y applicators, (which contain 2 radionuclides), the LV Y-90 Disc, is a single-source, disc-shaped device capable of being, assembled into clinical applicators (Fig. 21-1).36, For the purposes of this chapter, we will examine the, ocular use of beta-radiation-based brachytherapy for, ocular tumors and benign growths (Table 21-1). Beta-radiation, has been used to treat cancers such as choroidal, melanoma, RB, choroidal metastasis, conjunctival melanoma,, and conjunctival SCC.1,3,4,6,9,13,15,16,18,20-22,24,29,31,33-36, Beta-radiation has also been used to treat benign growths, such as uveal and retinal hemangioma (e.g., circumscribed, choroidal and retinal capillary angiomas) as, well as neovascular macular degeneration, eccentric, disciform degeneration, polypoidal choroidal vasculopathy,, pterygium, and as adjuvant for trabeculectomy, surgery.2,7,8,11,12,14,17-19,37-44, These reports include both LDR and HDR treatments., Of these, the most popularly known HDR 90Sr/90Y treatments, have been performed to prevent the recurrence, of pterygium.2,43,44 However, there also exists statistically, significant medical evidence that 90Sr/90Y has been used, as a tool to treat and prevent both the neovascularization, and fibrovascularization associated with failure of filtering, glaucoma surgery (e.g., trabeculectomy) in high-risk, patients compared to the antifibrotic drug 5-FU.8,13,14,42, Clearly, the literature shows that beta-radiation has been, effective for the treatment of both malignant ocular tumors, and benign growths., This chapter includes Liberty Vision’s experience creating, a new HDR 90Y beta-radiation brachytherapy system., It has been implemented by medical physics, radiation, oncology, and ophthalmology for the treatment of ocular, cancers.36 It is important to note that the 90Y radionuclide, has been previously used for the treatment of cancer in, the form of 90Y-laden glass or plastic microspheres arterially, perfused for radioembolization. Such 90Y treatments, have been directed toward hepatocellular carcinomas,, colon metastases, cholangiocarcinoma, and metastatic, choroidal melanoma. Such HDR 90Y brachytherapy offers, medical evidence of 90Y anticancer efficacy.45-50, Prior to bringing a new beta-radiation source to patient, care, Liberty Vision conducted preclinical studies examining, the dose distribution attributes of a variety of beta, sources. After choosing 90Y, Liberty Vision developed,, produced, and then obtained US Food and Drug Administration, (FDA) clearance for discrete 90Y disc sources to, be used in ophthalmic applicators.51 The clinical practice, parameters were then developed to implement this, new brachytherapy system. These included source calibration,, radiobiological dose derivation, sterilization,, assembly, radiation safety, and surgical techniques.36