Postoperative irradiation for pterygium: Guidelines for optimal treatment

doi:10.1016/0360-3016(92)90961-G

International Journal of Radiation OncologyBiologyPhysics

Volume 30, Issue 3, 15 October 1994, Pages 721-725

https://doi.org/10.1016/0360-3016(92)90961-G Get rights and content

Abstract

$Purpose$ : Postoperative adjuvant strontium-90 beta-ray therapy is a proven technique for reducing the recurrence rate of pterygium. A wide variety of doses and fractionation schemes have been used in the application of the radiation. There have been recent reports of significant rates of late-occurring complications after single-fractioned treatment. Compared with a single-dose application, fractionation would only offer a therapeutic benefit if recurrence prevention were an early-responding tissue phenomenon, in contrast to late-responding sequellae. We investigate this point with a view to elucidating better treatment protocols for postoperative beta-ray therapy for pterygium.

$Methods and Materials$ : We use the linear-quadratic formalism to analyze published nonrecurrence rates, as a function of dose and fraction number, to obtain a value for the parameter $α β$ , which is an indicator of whether nonrecurrence is an early or late-responding phenomenon.

$Results$ : The estimated value of the linear-quadratic parameter, α,β, is 25 Gy, with 90% confidence limits of ± 9 Gy. This large value unequivocally suggests that nonrecurrence is an early responding phenomenon, implying that fractionation should give an increased therapeutic ratio between nonrecurrence and late sequellae.

$Conclusions$ : Compared with a single-fractioned treatment, an improved therapeutic ratio (nonrecurrence vs. complications) would be expected from fractionated application of the beta-ray therapy. Given the parameters obtained from fitting literature data, we calculate guidelines for the dose/fraction schemes that should give equivalent disease control to different single-fraction applications, but should reduce the incidence of late-occurring sequellae.

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Brachytherapy is the treatment of disease using small radioactive sources placed in or near the tissues to be treated. This chapter explores some of the most common sources used for brachytherapy as well as their therapeutic applications. The delivered dose rate is one means utilized to categorize brachytherapy treatments into low, medium, or high dose-rate delivery. Further characterization is based on how long the sources are implanted, either as a temporary or a permanent implant. Several clinical examples are reviewed. Calculation methods, optimization and quality management are also discussed.
Low or high fractionation dose b-radiotherapy for pterygium? A randomized clinical trial: In regard to Viani GA et al. (Int J Radiat Oncol Biol Phys 2010;10.1016/j.ijrobp.2010.11.017)
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In reply to Drs. Mohamed and Thariat
2012, International Journal of Radiation Oncology Biology Physics
The role of radiotherapy in the treatment of pterygium: A review of the literature including more than 6000 treated lesions
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Citation Excerpt :
The use of a single radiation dose is reported here in three studies using doses from 20 to 30 Gy [11,35,76]. No or very low incidence of severe side effects were reported and good local control was achievable with rates of recurrence varied between 6.8 and 9.4%, but in view of the follow up periods of these studies, the higher rates of late side effects reported in other long term follow up studies and referring to the radiobiological work of Brenner et al. who estimated a large α/β value for disease control (25 ± 9 Gy), it is useful to design a multifractioned treatment that would be expected to give comparable control rates to a single fractioned treatment with less expected late complications [10,11,12,35,47]. Time between surgery and start of irradiation appears crucial in many studies, lower rates of recurrence were reported when irradiation initiated within 24 h after surgery and within 3 days versus more than 3 days postoperatively [21,35,55,57,62,66,75,77].
Pterygium is a benign conjunctival neoformation usually treated by surgical excision, but recurrences may affect 30% to 89% of cases, so that adjunctive therapies like conjunctival autografting, antimitotic drugs and beta-irradiation (β-irradiation) are often used to improve the rate of local control. Our essay has reviewed relevant studies addressing the role of postoperative irradiation in the treatment of pterygium in the last 30 years through an Internet-based search and hand search in libraries. Sixteen studies on β-irradiation and one on soft X-ray irradiation were accessible. They covered more than 6000 lesions treated by surgical excision and postoperative β-irradiation using strontium-90 (⁹⁰Sr) applicators at doses varying from 10 to 60 Gy/1–6 fractions/1–6 weeks starting within 3 days postoperatively. The rates of local recurrence were in general lower than 15% and major complications such as scleral thinning, ulceration, infections, or radiation-induced cataract were rarely encountered. Early postoperative β-irradiation at a dose of 30 Gy/three fractions/2–3 weeks starting within 24 h from surgical excision is an effective and safe procedure with local control rates comparable to chemotherapeutic agents and conjunctival autografting and superior to simple excision alone.
Le ptérygion est une tumeur bénigne d’origine conjonctivale. Son traitement est avant tout chirurgical, mais l’exérèse seule est grevée de près de 30 à 89 % de récidives, c’est pourquoi des traitements adjuvants comme l’autogreffe conjonctivale, les substances cytotoxiques, l’irradiation postopératoire au moyen de rayons bêta sont largement utilisées pour réduire ce risque de récidive. Nous avons cherché sur Internet et aussi dans les bibliothèques des études concernant le rôle de la radiothérapie postopératoire dans le traitement de ces lésions pendant les 30 dernières années. Seize études sur le traitement postopératoire à l’aide d’un émetteur bêta (strontium-90) et une seule étude sur les rayons X sont accessibles. Ces études ont inclus plus de 6000 lésions traitées au moyen de l’exérèse chirurgical suivie par une irradiation aux doses de 10 à 60 Gy en une à six séances sur une à six semaines débutées dans les trois jours postopératoires. Les taux de rechute ont globalement été inférieurs à 15 % et les effets secondaires majeurs comme l’atrophie de la sclère, l’ulcération, des infections et la cataracte ont rarement été reportées. Cette revue permet de conclure que l’irradiation postopératoire précoce (notamment l’irradiation bêta), à une dose de 30 Gy en trois fractions et deux à trois semaines, débutée dans les 24 heures suivant l’acte chirurgical, est un traitement efficace et sans effets secondaires majeurs, assurant un taux de contrôle local comparable à celui obtenu par les injections locales de substances cytotoxiques ou par l’autogreffe conjonctivale, et significativement supérieur à celui obtenu par l’exérèse chirurgicale seule.
Long term results of non-surgical, exclusive strontium-/yttrium-90 beta-irradiation of pterygia
2005, Radiotherapy and Oncology
To evaluate long term results and to demonstrate safety and efficacy of non-surgical, exclusive strontium-/yttrium-90 beta irradiation of non-operated pterygia.
Between March 1977 and April 1999, 43 patients with 54 primary pterygia were treated with an exclusive strontium-/yttrium-90 beta-irradiation up to a total dose of 50 Gy divided in four fractions with one week apart. All patients were referred from the same ophthalmologist. The average follow-up were 112(±88 months (range, 12–321 months), median 96 months.
The patients were referred with early symptomatic manifestations of pterygia with a mean horizontal diameter of 1.6±0.7 mm (range, 0.5–4.5 mm), which shrank to a mean diameter of 0.9±0.6 mm (range, 0–2.5 mm) after irradiation (P<0.005). There was a reduction of size in every pterygium, none of the 54 pterygia developed a recurrent growth and there were no patient with any late side effect. Following the strontium-/yttrium-90 application the process came up with an obliteration of the vessels, which resulted in a grey, thin and avascular pannus.
Strontium-/yttrium-90 beta-irradiation as an exclusive, non-surgical treatment for early pterygia provides a significant reduction of the size of the irradiated pterygia, is a safe and effective therapy to prevent a recurrence and can be performed without late side effects.
Prevention of pterygium recurrence by postoperative single-dose β-irradiation: A prospective randomized clinical double-blind trial
2004, International Journal of Radiation Oncology Biology Physics
To affirm the effectiveness and complication rate of postoperative single-dose β-irradiation (RT) with ⁹⁰Sr in the case of primary pterygium in a clinical trial. Pterygium is a benign disease of the supporting orbital tissue that can cause impairment of visual function. Depending on the technique used for surgery, recurrence is described in up to 70% of cases—a reason to combine the initial treatment with radiotherapy or chemotherapy.
This trial was designed as a prospective, randomized, multicenter, double-blind study. Surgery was performed in all cases according to the bare sclera technique. Ninety-one patients with 96 pterygia were postoperatively randomized to either β-RT or sham RT. In the case of β-RT, a ⁹⁰Sr eye applicator was used to deliver 2500 cGy to the sclera surface at a dose rate of between 200 and 250 cGy/min. Sham RT was given using the same type of applicator without the ⁹⁰Sr layer. After treatment, both an ophthalmologist and a radiation oncologist performed the follow-up examinations. The accumulated data were analyzed using a group sequential test.
Between February 1998 and September 2002, 96 eyes with primary pterygium were operated on according to the trial protocol. Additional treatment was performed within 24 hours postoperatively. Ten patients were lost to follow-up, resulting in 86 patients who could be analyzed. In the 44 eyes randomized to receive β-RT, 3 relapses occurred compared with 28 recurrences in the 42 eyes that received sham RT, for a crude control rate of 93.2% vs. 33.3%, respectively. At a mean follow-up of 18 months, major treatment complications had not been observed.
Single-dose β-RT after bare sclera surgery is a simple, effective, and safe treatment that reduces the risk of primary pterygium recurrence.

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Oncology intelligencePostoperative irradiation for pterygium: Guidelines for optimal treatment

Abstract

Ophthalmology

Int. J. Radiat. Oncol. Biol. Phys.

Br. J. Radiol.

Br. J. Ophthalmol.

South. Med. J.

Trans. Ophthalmol. Soc. Aust.

Use of postoperative beta radiation in the treatment of pterygium

Ophthalmic Surg.

Determination of surface dose rate from a 90Sr applicator

Med. Phys.

Postoperative beta radiation treatment of pterygium

Int. J. Radiat. Oncol. Biol. Phys.

Pterygia: Single-fraction postoperative beta irradiation

Radiology

Recurrent pterygia: Results of postoperative treatment with Sr-90 applicators

Radiology

Beta-irradiation of pterygia: Comparison of different areas treated

Br. J. Ophthalmol.

Pterygium Throughout the World

Postoperative irradiation of pterygia. An unexpected effect of the time/dose relationship

Radiology

Oncology intelligence
Postoperative irradiation for pterygium: Guidelines for optimal treatment

Determination of surface dose rate from a ⁹⁰Sr applicator