33. Pterygium - The GEC-ESTRO Handbook of Brachytherapy

Pterygium

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 01/03/2023

33 Pterygium

Bruno Fionda, Monica Maria Pagliara, Ramin Jaberi

1. Summary 2. Introduction 3. Anatomy 4. Pathology

3 3 3 4 4 4 4 4

9. Treatment planning

4 6 6 6 6 6 8

10. Dose, dose rate and fractionation

11. Monitoring

12. Results

5. Work up

13. Adverse Events 14. Key messages 15. References

6. Indications, contra-indications 7. Clinical Target Volume

8. Technique

1. SUMMARY

Pterygium is an ocular surface disease characterized by a wing-shaped growth of limbal and conjunctival tissue, within the palpebral fissure, with progressive involvement of the cornea. After primary pterygium surgery there is a high risk of recurrence, therefore, adjuvant treatment after surgical excision should be considered. Adjuvant irradiation, delivered immediately after surgery, can effectively prevent pterygium recurrence. The standard and classical technique is using a beta emitter (such as strontium-90) applicator which is an epibulbar shape and adapted to the target volume as closely as possible.

2. INTRODUCTION

the cornea in the direction of the growing pterygium (especially for lesions>2mm) [5]. In advanced cases, pterygium can affect vision as it invades the cornea with the potential to obscure the optical centre of the cornea. After primary pterygium surgery there is a high risk of recurrence in the range of 24% to 89%, therefore adjuvant treatment after surgical excision should be considered [6].

Using beta radiation sources has a long history of successful treatments that have been published in radiotherapy and ophthalmology. It is a convenient and practical method of applying radiation and has the advantage of minimal tissue penetration. Today, this well-established local radiotherapy method has undergone a revival [1]. Several authors have emphasised that adjuvant radiotherapy is practical, effective and owing to its long history, we are more aware of its long-term effects than is the case with other modalities [2]. Pterygium is an ocular surface disease characterized by a wing- shaped growth of limbal and conjunctival tissue, within the palpebral fissure, with progressive involvement of the cornea. Risk factors for developing pterygium include demographic, environmental, and lifestyle factors [3]. Since the main risk factor for the development and the progression of pterygium is ultraviolet exposure, the prevalence varies with geographical location and ranges from 1% to more than 30% [4]. Though frequently asymptomatic, if it becomes inflamed, irritation and dry eye, by interrupting the tear film can occur. In later stages, the growing tissue may cause astigmatism by flattening

3. ANATOMY

Pterygiummay be located from the cornea to the internal cantus, in the interpalpebral opening [7]. Critical organs for radiotherapy are all the structures of the eye in particular the lens. When radiation is used the dose received by the lens and other critical sites in the anterior eye segment must be strictly evaluated. A schematic representation is presented in figure 1.