Postoperative irradiation of primary or recurrent pterygium: results and sequelae

Radiation Therapy for Benign Disease: Keloids, Macular Degeneration, Orbital Pseudotumor, Pterygium, Peyronie Disease, Trigeminal Neuralgia

Although the use of ionizing radiation on malignant conditions has been well established, its application on benign conditions has not been fully accepted and has been inadequately recognized by health care providers outside of radiation therapy. Most frequently, radiation therapy in these benign conditions is used along with other treatment modalities, such as surgery, when the condition causes significant disability or could even lead to death. Radiation therapy can be helpful for inflammatory/proliferative disorders. This article discusses the present use of radiation therapy for some of the most common benign conditions.

Comparison of trabeculectomy and trabeculectomy with amniotic membrane transplantation in the same patient with bilateral glaucoma

AIM

To observe effects of trabeculectomy with amniotic membrane transplantation (AMT) in controlling postoperative intraocular pressure (IOP) in patients with medically uncontrolled glaucoma.

METHODS

This study included adult patients with requiring bilateral glaucoma surgery. Each patient underwent trabeculectomy (Non-AMT group) in one eye and with AMT (AMT group) in the other eye according to randomized principle. Success was defined as intraocular pressure (IOP)<21mmHg without any anti-glaucoma medications at 24 months follow-up. The two groups were compared in terms of IOP, complications and success rate.

RESULTS

Thirty-four eyes of 17 patients were investigated in this study. There was no statistically signifcant difference in pre-operative IOP between the two groups. The mean IOP was lower in AMT group compared with Non-AMT group on follow up months 12, 18, and 24.Postoperative complications were more frequent in Non-AMT group (35.3%, 6/17) compared with AMT group (5.9%, 1/17). The success rate of surgery was 88.2% (15/17) in Non-AMT group and 100% (17/17) in AMT group.

CONCLUSION

Trabeculectomy with AMT is an effective procedure to reduce IOP and complications, thereby improving surgical success rates.

Intra-lesional 5 fluorouracil for the management of recurrent pterygium

AIM

Recurrence is the most common complication arising from pterygium surgery. The aim of this study was to investigate the effectiveness of 5 fluorouracil (5FU) in halting the recurrence of pterygium after surgical excision.

METHODS

A retrospective review of patients treated for pterygium recurrence was carried out. Patients with recurrent (secondary) pterygium were treated with multiple weekly intra-lesional injections of 0.1-0.2 ml (2.5-5 mg) 5FU post-operatively depending on the size of the recurrence. The treatment was started within 1 month from the date of recurrence. The time from surgery to start of recurrence, previous treatment modalities, and number of recurrences were documented. The number of injections required to induce arrest of progression and/or regression of vascularity and fleshiness of the pterygium and any complications related to 5FU treatment were examined.

RESULTS

Fifteen eyes from 14 patients with recurrent pterygium treated with intra-lesional 5FU injections were analysed. Three of the 15 eyes had undergone a secondary excision and 12 had undergone a primary excision. In all, 93.3% of patients showed regression of the fibrovascular tissue (thickness and vascularity) and arrest of progression following a dose of 0.1-0.2 ml (2.5-5 mg) 5FU. Twelve eyes required three injections or fewer, whereas one patient required eight injections. This beneficial effect was maintained over an average follow-up period of 17 months. No complications from 5FU were observed.

CONCLUSION

The use of weekly intra-lesional 5FU injections for the treatment of recurrent pterygium is safe and effective in limiting the progression and inducing the regression of recurrent pterygium. The number of injections can be tailored according to clinical need.

Low-dose strontium-90 irradiation is effective in preventing the recurrence of pterygia: a ten-year study

Background

To study the long-term effects of low-dosage strontium-90 (Sr90) irradiation on the recurrence of pterygium.

Methodology/Principal Findings

One hundred twenty eyes from 104 patients with primary or recurrent pterygia were treated with surgery followed by Sr90 irradiation. In brief, starting on the sixth day after surgery, patients were treated with irradiation three times every other day at a total combined dosage of 2000 cGy to 3000 cGy. Corneal topography was used to evaluate ocular surface regularity before and after treatment. Patient follow-up was performed 2 days, 5 days, 2 weeks, 1 month, 3 months, 1 year, 5 years, and 10 years after surgery. Recurrence of pterygium was not observed in any of the patients in this study. Obvious cataract progression was observed in 6 eyes, which may be due to aging. During follow-up studies, only one eye was reported with dryness and foreign-body sensation. Significant pterygium-induced astigmatism was observed in corneal topography, which decreased after surgery.

Conclusions/Significance

Sr90 irradiation is effective in preventing the recurrence of primary and recurrent pterygia. We recommend delivering a total combined dosage of 2000 cGy to 3000 cGy of Sr90 irradiation administered in three batches every other day starting from the sixth day after surgery. Surgery is important in the rapid recovery of the cornea from pterygium-induced astigmatism.

Reirradiation of spinal column metastases: comparison of several treatment techniques and dosimetric validation for the use of VMAT

BACKGROUND

For reirradiation of spinal column metastases, intensity-modulated radiation therapy (IMRT) reduces the dose to the spinal cord, while allowing longer treatment times. We analyzed the potential of volumetric modulated arc therapy (VMAT) to reduce treatment time and number of monitor units (MU).

PATIENTS AND METHODS

In CT datasets of 9 patients with spinal column metastases, the planned target volume (PTV) encompassed the macroscopic tumor including the spinal cord or medullary cone, respectively. The prescribed dose for the target was 40 Gy, but median spinal cord dose was intended to be < 26 Gy. We compared a posterior (3D-PA) static field technique, a two-field wedge technique (3D-wedge) and 5-/7-beam IMRT with VMAT. Conformity index (CI), homogeneity index (HI40), dose volume histogram (DVH) parameters, treatments delivery time (T), and MU were analyzed. Dosimetry was validated with EDR2-film/ionization chambers.

RESULTS

PTV coverage was insufficient for 3D-conformal radiotherapy (3D-CRT) when spinal cord tolerance was respected. The IMRT approach provided excellent results but has the longest treatment time. VMAT produced dose distributions similar to IMRT with shorter treatment times (VMAT: mean 4:49 min; IMRT: mean 6:50 min) and fewer MU (VMAT: 785; IMRT: 860). Reduced conformity and increased homogeneity for VMAT when compared to IMRT were observed. An absolute deviation between measured and calculated dose of +0.70 ± 3.69% was recorded. γ-Index analysis showed an agreement of 91.33 ± 3.53% for the 5%/5 mm criteria.

CONCLUSION

For this paradigm, VMAT produces high quality treatment plans with homogeneity/conformity similar to static IMRT, shorter treatment times, and fewer MU. Verification measurements showed good agreement between calculation and delivered dose, leading to clinical implementation.

Dose-effect relationships for recurrence of keloid and pterygium after surgery and radiotherapy

PURPOSE

To show radiation dose-response relationships for recurrence of keloid and pterygium after radiotherapy following surgery.

METHODS AND MATERIALS

Using PubMed, we performed a retrospective review of articles reporting incidences and/or dose-response relationships for recurrence of keloid and pterygium after radiotherapy following surgery. The irradiation regimens identified were normalized by use of the linear-quadratic model; biologically effective doses (BEDs) were calculated.

RESULTS

For keloid recurrence after radiotherapy following keloid removal, with either teletherapy or brachytherapy, the recurrence rate after having delivered a BED greater than 30 Gy is less than 10%. For pterygium recurrence after bare sclera surgery and (90)Sr beta-irradiation, a BED of about 30 Gy seems to be sufficient also to reduce the recurrence rate to less than 10%.

CONCLUSIONS

Most of the doses in the radiotherapy schemes used for prevention of keloid recurrence after surgery are too low. In contrast, the doses applied in most regimens to prevent pterygium recurrence are too high. A scheme with a BED of 30 to 40 Gy seems to be sufficient to prevent recurrences of keloid as well as pterygium.

Ophthalmic and adnexal complications of radiotherapy

The role of radiotherapy in ophthalmic practice continues to grow. This growth has seen an expansion of indications for radiotherapy, a refinement of the modalities that can be used and a reduction in the ocular and adnexal complications that result from this form of therapy. The compendium of indications for radiotherapy in ophthalmology continues to grow and now includes many conditions such as the treatment of lid and adnexal disease, ocular surface disorders and both benign and malignant disease of the posterior segment and optic pathways. The radiotherapeutic modalities employed to manage these conditions are numerous and include both radioactive plaques (brachytherapy) and external beam radiation techniques. New techniques such as stereotactic radiosurgery are delivering benefits in the management of conditions such as optic nerve sheath meningioma, where the treatment of this blinding and occasionally life-threatening intracranial neoplasm now results in fewer adverse affects. The purpose of this review is to give a brief overview of the indications and treatment modalities, and a more in-depth discussion of the potential side-effects when radiotherapy is used for ocular and periorbital disease.

The role of radiation therapy in benign diseases

Although adequate prospective data are lacking, radiation therapy seems to be effective for many benign diseases and remains one of the treatment modalities in the armamentarium of medical professionals. Just as medication has potential adverse effects, and surgery has attendant morbidity, irradiation sometimes can be associated with acute and chronic sequelae. In selecting the mode of treatment, most radiation oncologists consider the particular problem to be addressed and the goal of therapy in the individual patient. It is the careful and judicial use of any therapy that identifies the professional. With an understanding of the current clinical data, treatment techniques, cost, and potential detriment, the goal is to provide long-term control of the disease while minimizing unnecessary treatment and potential risks of side effects. The art lies in balancing benefits against risks.

A special mini-extrapolation chamber for calibration of90Sr+90Y sources

90Sr+90Y applicators are commonly utilized in brachytherapy, including ophthalmic procedures. The recommended instruments for the calibration of these applicators are extrapolation chambers, which are ionization chambers that allow the variation of their sensitive volume. Using the extrapolation method, the absorbed dose rate at the applicator surface can be determined. The aim of the present work was to develop a mini-extrapolation chamber for the calibration of 90Sr+90Y beta ray applicators. The developed mini-chamber has a 3.0 cm outer diameter and is 11.3 cm in length. An aluminized polyester foil is used as the entrance window while the collecting electrode is made of graphited polymethylmethacrylate. This mini-chamber was tested in 90Sr+90Y radiation beams from a beta particle check source and with a plane ophthalmic applicator, showing adequate results.

5-fluorouracil vs. beta-irradiation in the prevention of pterygium recurrence

The aim of this study was to compare 5-fluorouracil (5-FU) with beta-irradiation in the prevention of pterygium recurrence. A retrospective non-randomised review of cases of fleshy pterygium treated with bare scleral excision and adjuvant 5-FU were compared with similar morphologically appearing pterygia, matched for age and sex, treated with bare scleral excision and adjuvant beta-irradiation. All surgeries were carried out at the university college hospital and Ojulowo eye hospital, Ibadan, Nigeria. Twenty-seven eyes of 24 patients who had pterygium excision with adjuvant treatment with 5-FU were compared with 31 eyes of 24 patients who were treated with excision and beta-irradiation. The mean age for the 5-FU group was 46.1 years while that for the beta-irradiation group was 46.9 years. Both sexes were equally represented, 12 males and 12 females. There were seven (25.9%) initial recurrences in the 5-FU group but four of these became atrophic, and therefore, cosmetically acceptable leaving three eyes (11%) with unacceptable recurrent pterygia. The beta-irradiation group, however, had seven (22.5) initial recurrence but five of these became atrophic and fell short of the cornea, leaving two (6.5%) with clinically unacceptable recurrence. The difference was, however, not statistically significant (Zc = 0.74 and p > 0.1). The associated complications were mostly mild in both groups and included cornea opacity of 10 (37%) complications, conjunctivitis of three (11%) complications, sclera granuloma of three (11%) complications and conjunctiva necrosis of one (3.7%) complication for the 5-FU group, and while the beta-irradiation group had corneal opacity of one (3.7%) complication and conjunctivitis of three (11%) complications. The non-statistical significance of a lower-pterigium recurrence rate with use of beta-irradiation for the treatment of fleshy pterygium compared with 5-FU may have been partly due to the small number of patients studied. A randomised-controlled study using a larger sample size is therefore proposed. However, the fact that over half of those with initial recurrence in the 5-FU group became atrophic (and therefore cosmetically acceptable) over time as well as less cost implication in the purchase of 5-FU relative to Strontium-90 association with few and mild complications makes it a desirable adjuvant therapy in depressed economies. However, beta-irradiation still has a place when cost issue is not an inhibiting factor in view of its clinically superior outcome.

Prevention of pterygium recurrence by postoperative single-dose β-irradiation: a prospective randomized clinical double-blind trial

PURPOSE

To affirm the effectiveness and complication rate of postoperative single-dose beta-irradiation (RT) with (90)Sr 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.

METHODS AND MATERIALS

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 beta-RT or sham RT. In the case of beta-RT, a (90)Sr 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 (90)Sr 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.

RESULTS

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 beta-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.

CONCLUSION

Single-dose beta-RT after bare sclera surgery is a simple, effective, and safe treatment that reduces the risk of primary pterygium recurrence.