External beam irradiation for retinoblastoma: patterns of failure and dose-response analysis

Management of Extraocular Retinoblastoma: ICMR Consensus Guidelines

Retinoblastoma (RB) is the most common intraocular malignancy of childhood. Advanced stage presentation of RB is common in low middle-income countries (LMICs) due to lack of awareness, social taboos associated with enucleation, seeking alternative conservative treatment options, and poor accessibility to health care. Over the last few decades, there have been significant advancements in the management of extraocular RB (EORB) which have improved outcomes and helped in minimizing treatment-related toxicities. The incorporation of multimodality approaches including chemotherapy, surgery, and radiotherapy (RT) has shown promising results; however, prognosis remains poor especially in LMICs. In this article, authors have discussed the ICMR consensus guidelines on the management of EORB, including metastatic RB.

Current Indications of Secondary Enucleation in Retinoblastoma Management: A Position Paper on Behalf of the European Retinoblastoma Group (EURbG)

Simple Summary

Although secondary enucleation (SE) is the treatment of choice for retinoblastoma eyes that did not respond favorably to conservative therapies, clear criteria for its indication are, however, currently missing. In this position paper on behalf of the European Retinoblastoma Group (EURbG), we discuss the available literature on SE, including its influence on metastases rate and survival, and propose guidelines to assist decision-making to interrupt eye-preserving therapies depending on the availabilities of advanced diagnostic and therapeutic modalities. Absolute indications to SE may be restricted to eyes with refractory tumor activity resisting all salvage treatments or eyes under apparent tumor control but no visual potential and irreducible complications. In contrast, eyes with an obscured optic nerve head and/or ocular complications amenable to specific surgical or medical management can be considered relative indications, provided that appropriate follow-up can be implemented and that parents are fully aware of a residual risk.

Abstract

Secondary enucleation (SE) puts an irreversible end to eye-preserving therapies, whenever their prolongation is expected to violate the presumed state of metastatic grace. At present, it must be acknowledged that clear criteria for SE are missing, leading to empiric and subjective indications commonly related to disease progression or relapse, disease persistence masking the optic nerve head or treatment-related complications obscuring the fundus view. This absence of evidence-based consensus regarding SE is explained by the continuously moving frontiers of the conservative management as a result of diagnostic and therapeutic advances, as well as by the lack of studies sufficiently powered to accurately stratify the risk of metastasis in conservatively treated patients. In this position paper of the European Retinoblastoma Group (EURbG), we give an overview of the progressive shift in the indications for SE over the past decades and propose guidelines to assist decision-making with respect to when SE becomes imperative or recommended, with corresponding absolute and relative SE indications. Further studies and validation of biologic markers correlated with the risk of metastasis are expected to set more precisely the frontiers of conservative management and thus consensual criteria for SE in the future.

Episcleral brachytherapy for retinoblastoma

BACKGROUND/AIMS

To report visual outcomes, survival outcomes and complications following episcleral brachytherapy (EB) for retinoblastoma.

METHODS

Retrospective review of retinoblastoma cases treated with EB in a single institution. Survival outcomes were analysed using the Kaplan-Meier method.

RESULTS

Eleven tumours of 11 eyes were treated with either iodine-125 or ruthenium-106 EB with a mean apical dose of 44 Gy. The tumours were classified as group B in 5 (46%), C in 3 (27%) or D in 3 (27%) eyes, respectively. Mean follow-up time was 75.4 months. EB served as primary treatment in 3 eyes (27%) and secondary treatment in 8 eyes (73%). Final visual acuity was better than 20/200 in 70% of cases. Globe preservation was achieved in 9 (82%) eyes. Local recurrence occurred in 18% of cases at a mean onset of 17.4 months after EB. Two group D tumours that recurred after secondary EB underwent enucleation. Mean onset of radiation retinopathy was 17.4 months following EB. No metastatic or fatal events were recorded. Kaplan-Meier analysis showed recurrence-free survival and ocular survival of 80% and overall survival of 100% at 5 years after EB.

CONCLUSION

EB is an effective primary or secondary treatment modality for selected retinoblastoma eyes (groups B and C). Advanced group D tumours may represent a risk factor for local recurrence. Visually significant complications such as radiation retinopathy should be anticipated.

Lens Dose-Response Prediction Modeling and Cataract Incidence in Patients With Retinoblastoma After Lens-Sparing or Whole-Eye Radiation Therapy

PURPOSE

We retrospectively assessed the incidence of cataracts in patients with retinoblastoma (Rb) treated with either lens-sparing radiation therapy (LSRT) or whole-eye radiation therapy (WERT). A secondary aim of this study was to model the dose-response risk of cataract.

METHODS AND MATERIALS

We reviewed 65 patients with Rb treated with radiation therapy (RT) at Children's Hospital, Los Angeles from 1997 to 2015. Eyes that were enucleated before RT or lacked follow-up eye examinations were excluded. All patients underwent computed tomography simulation, and mean lens dose data were collected. Follow-up ophthalmologic examinations and intraocular lens implant history were reviewed for cataracts. The primary event-free survival (EFS) outcome was cataract development. Eyes without cataracts were censored on the last date of eye examination or post-RT enucleation, if applicable. Kaplan-Meier estimates were used to compare EFS outcomes, and dose response was projected with Cox regression and logistic regression models.

RESULTS

Sixty-one patients (94 eyes) were analyzed with a median follow-up of 51.8 months. For eyes treated with WERT, cataracts developed in 71.7% versus 35.3% for LSRT. Median EFS for WERT and LSRT were 20.8 and 67.9 months, respectively. Compared with WERT, a significant EFS benefit was demonstrated for LSRT (P < .001). Mean lens dose had a significant effect on cataracts in both Cox regression and logistic regression models (P < .01). The mean lens dose of 7 Gy was projected to have a 5-year cataract incidence of 20% and 25% with the logistic and Cox regression models, respectively.

CONCLUSIONS

We report the first clinical data demonstrating significantly improved EFS in patients with Rb treated with LSRT. Through lens dose-response modeling, we validate a mean lens dose threshold of 7 Gy to keep cataract risk below 25%. Although RT is used less often for Rb owing to advances in chemotherapy delivery options, these findings are relevant for refining lens dose constraints, particularly in children who have received radiation dose near the orbit.

A review of the literature for intra-arterial chemotherapy used to treat retinoblastoma

Retinoblastoma is a malignancy of the retina that usually presents before the age of 5 years. Sporadic retinoblastoma is most often unilateral and with no hereditary influence, whereas familial retinoblastoma presents unilaterally or bilaterally in conjunction with genetic inheritance. Several treatments have been attempted with the goals of saving the child's life, salvaging the eye, and preserving vision. Alternative methods including external beam radiation, systemic chemotherapy and focal therapies have been shown to be effective but carry a risk of enucleation and other complications proportional to the severity of the tumor. Selective intra-arterial chemotherapy for retinoblastoma began in 1988 in Japan and has emerged in the last 7 years in the United States as a feasible, effective and minimally invasive treatment option. We review the retinoblastoma treatment literature focusing on intra-arterial chemotherapy.

Treatment of Retinoblastoma: The Role of External Beam Radiotherapy

The risk of radiotherapy-related secondary cancers in children with constitutional retinoblastoma 1 (RB1) mutations has led to reduced use of external beam radiotherapy (EBRT) for RB. Presently, tumor reduction with chemotherapy with or without focal surgery (chemosurgery) is most commonly undertaken; EBRT is avoided as much as possible and is considered only as the last treatment option prior to enucleation. Nevertheless, approximately 80% of patients are diagnosed at a locally advanced stage, and only 20-25% of early stage RB patients can be cured with a chemosurgery strategy. As a whole, chemotherapy fails in more than two-thirds of eyes with advanced stage disease, requiring EBRT or enucleation. Radiotherapy is still considered necessary for patients with large tumor(s) who are not candidates for chemosurgery but who have visual potential. When radiation therapy is indicated, the lowest possible radiation dose combined with systemic or local chemotherapy and focal surgery may yield the best clinical outcomes in terms of local control and treatment-related toxicity. Proton beam therapy is one EBRT method that can be used for treatment of RB and reduces the radiation dose delivered to the adjacent orbital bone while maintaining an adequate dose to the tumor. To maximize the therapeutic success of treatment of advanced RB, the possibility of integrating radiotherapy at early stages of treatment may need to be discussed by a multidisciplinary team, rather than considering EBRT as only a last treatment option.

Leptomeningeal failure of retinoblastoma

Leptomeningeal (LM) failure of retinoblastoma (Rb) has not previously been reported. Upon review of our institutional experience of external beam radiotherapy (EBRT) for Rb, we found three LM failures. We sought to better define the clinical parameters of this type of recurrence. All children with LM failure had Reese-Ellsworth stage Vb eyes. Otherwise, no variables were significantly associated with LM failure. We theorize that this phenomenon is a function of the late-stage eyes for which EBRT is being reserved in the modern era.

Predictors of long-term visual outcome after chemoreduction for management of intraocular retinoblastoma

BACKGROUND

  To determine the predictors of long-term visual outcome after chemoreduction for management of intraocular retinoblastoma.

DESIGN

  Retrospective case series.

PARTICIPANTS

  One hundred and forty eyes of 96 new retinoblastoma patients.

METHODS

  The clinical records were reviewed for demographical profile, tumour characteristics, treatment methods, treatment side effects and final visual outcome. Multivariate analysis was used to evaluate factors predictive of final visual acuity.

MAIN OUTCOME MEASURE

  The clinical data were analysed for main outcome measures of good vision (visual acuity ≥6/12) or ambulatory vision (visual acuity ≥6/60). The correlation among predictor variables was determined using Pearson's product moment correlation for continuous variables, and t-test and analysis of variance test for categorical baseline variables.

RESULTS

  Follow-up ranged from 2 years to 14 years (median 75 months). The final mean logarithm of minimum angle of resolution visual acuity was 0.79. Ambulatory vision (≥6/60) was achieved in 100 of 140 (71%) eyes, and vision of ≥6/12 was seen in 52 eyes (37%). Extrafoveolar tumour and greater number of tumours in the eye were the only predictors of visual acuity ≥20/40. Greater number of tumours correlated with smaller mean basal tumour diameter. The mean basal tumour diameter was 9.8 mm in eyes with multiple tumours and 12.2 mm in eyes with single tumours (P = 0.03).

CONCLUSION

  Long-term ambulatory vision (≥6/60) was achieved in the majority (71%) of retinoblastoma containing eyes not requiring enucleation after treatment with chemoreduction and adjunctive therapy. Absence of foveolar involvement and greater number of tumours were the predictor of long- term visual outcome of 6/12 or better.

Intensity modulated radiotherapy (IMRT) in bilateral retinoblastoma

Background

External beam radiotherapy (EBRT) for retinoblastoma has traditionally been done with conventional radiotherapy techniques which resulted high doses to the surrounding normal tissues.

Case report

A 20 month-old girl with group D bilateral retinoblastoma underwent intensity modulated radiotherapy (IMRT) to both eyes after failing chemoreduction and focal therapies including cryotherapy and transpupillary thermotherapy. In this report, we discuss the use of IMRT as a method for reducing doses to adjacent normal tissues while delivering therapeutic doses to the tumour tissues compared with 3-dimensional conformal radiotherapy (3DCRT). At one year follow-up, the patient remained free of any obvious radiation complications.

Conclusions

Image guided IMRT provides better dose distribution than 3DCRT in retinoblastoma eyes, delivering the therapeutic dose to the tumours and minimizing adjacent tissue damage.

Current management strategies for intraocular retinoblastoma

Survival rates for retinoblastoma patients have increased dramatically over the last century, with documented 5-year survival figures reaching 87-99% in developed countries. During the last decade, there has been a dramatic paradigm shift in the treatment approach for intraocular retinoblastoma, emphasising chemoreduction protocols and minimising the use of external beam radiation. The recognition of the increased risk for second non-ocular cancers with external beam radiation contributed to the growing emergence of chemotherapy. Although chemoreduction protocols vary slightly between institutions, many centres are currently treating intraocular retinoblastoma with carboplatin, vincristine and etoposide as a three-drug regimen given in two to six cycles. Clinical studies have demonstrated that systemic chemotherapy must be combined with other modalities, such as laser treatment and cryotherapy, for adequate tumour control and many eyes with advanced intraocular disease require salvage therapy with radiation or enucleation. Therefore, modern centres treating retinoblastoma continue to manage patients with a variety of modalities, individualising the therapy according to the patient's presentation and clinical course.

Retinoblastoma—comparative analysis of external radiotherapy techniques, including an IMRT technique

PURPOSE

To compare the numerous external radiotherapy (RT) techniques for the treatment of retinoblastoma, as well as an intensity-modulated RT (IMRT) technique. The latter was elaborated to evaluate the potential dose reduction in the surrounding tissue, as well as the potential avoidance of subdosage in the ora serrata retinae.

METHODS AND MATERIALS

A 2-year-old patient with unilateral retinoblastoma underwent CT. With the aid of an ophthalmologist, the ocular structures were delimited, and 13 techniques described in published reports were reproduced on three-dimensional planning software and identified according to their authors. A technique with four noncoplanar fields using IMRT was also elaborated. These techniques were compared according to the dose to the ora serrata retinae, lens, orbit (volume that received a dose of >or=20 Gy), vitreous, optic nerve, lacrimal gland (volume that received a dose of >or=34 Gy), and cornea and according to their ease of reproducibility.

RESULTS

The techniques that attained the therapeutic dose to the ora serrata retinae were the IMRT technique and the techniques of Haye, Cassady, Cormack, and al-Beteri. The Cormack technique had the lowest volume that received a dose of >or=20 Gy in the orbit, followed by the IMRT technique. The IMRT technique also achieved the lowest volume that received a dose of >or=34 Gy (14%) in the lacrimal gland. The Abramson/McCormick/Blach, Cassady, Reese, and Schipper techniques were the easiest to reproduce and the Chin the most complex.

CONCLUSION

Retinoblastoma treatment with IMRT has an advantage over the other techniques, because it allows for the greatest reduction of dose to the orbit and lacrimal gland, while maintaining the therapeutic dose to the ora serrata retinae and vitreous.

Focal Stereotactic External Beam Radiotherapy as a Vision-sparing Method for the Treatment of Peripapillary and Perimacular Retinoblastoma: Preliminary Results

AIMS

Chemotherapy with aggressive focal ablative therapy is now the mainstay of retinoblastoma therapy. Our experience presents an evolution from conventional radiotherapy by treating posterior pole tumours with focal stereotactic fractionated radiotherapy (SRT).

MATERIALS AND METHODS

A retrospective chart review was conducted of five patients (six eyes) treated with SRT at the Hospital for Sick Children and Princess Margaret Hospital, Toronto, Canada, between 1999 and 2004. The prescribed dose was 40 Gy delivered in 20 fractions once daily using 6 MV photons.

RESULTS

Five patients (six eyes) were treated. The median age at the time of SRT was 18 months. The median follow-up was 46.5 months as of September 2004. Four patients were treated for a posterior pole focal tumour by focal SRT, and one patient was treated for vitreous seeding with whole-eye SRT. In patients treated with focal SRT, the median doses to the tumour, optic chiasm and brainstem were 41.92, 0.25 and 0.07 Gy, respectively, and to the ipsilateral optic nerve, globe and lens were 9.98, 19.11 and 3.74 Gy, respectively. The median doses to the ipsilateral and contralateral orbital bone were 6.73 Gy (range 5.99-8.29 Gy) and 2.31 Gy (range 0.88-7.08 Gy), respectively. A complete response (residual inactive scar tissue) was seen in four of the five focal tumours treated, with one tumour responding with a partial response (suspicious residual scar tissue). No acute or late side-effects occurred in patients treated with focal SRT. Only the patient treated with whole-eye SRT developed late effects of cataract and corneal ulceration. One patient suffered recurrence within the radiation field 5 months after focal SRT. Control of this recurrence was successful using chemotherapy and focal therapy. No eye has been enucleated.

CONCLUSION

Vision-sparing focal SRT for localised tumour masses in critical locations can control tumours with minimal side-effects and a minimal dose to the surrounding critical normal tissue.

Proton radiation therapy for retinoblastoma: Comparison of various intraocular tumor locations and beam arrangements

PURPOSE

To study the optimization of proton beam arrangements for various intraocular tumor locations; and to correlate isodose distributions with various target and nontarget structures.

METHODS AND MATERIALS

We considered posterior-central, nasal, and temporal tumor locations, with straight, intrarotated, or extrarotated eye positions. Doses of 46 cobalt grey equivalent (CGE) to gross tumor volume (GTV) and 40 CGE to clinical target volume (CTV) (2 CGE per fraction) were assumed. Using three-dimensional planning, we compared isodose distributions for lateral, anterolateral oblique, and anteromedial oblique beams and dose-volume histograms of CTVs, GTVs, lens, lacrimal gland, bony orbit, and soft tissues.

RESULTS

All beam arrangements fully covered GTVs and CTVs with optimal lens sparing. Only 15% of orbital bone received doses > or =20 CGE with a lateral beam, with 20-26 CGE delivered to two of three growth centers. The anterolateral oblique approach with an intrarotated eye resulted in additional reduction of bony volume and exposure of only one growth center. No appreciable dose was delivered to the contralateral eye, brain tissue, or pituitary gland.

CONCLUSIONS

Proton therapy achieved homogeneous target coverage with true lens sparing. Doses to orbit structures, including bony growth centers, were minimized with different beam arrangements and eye positions. Proton therapy could reduce the risks of second malignancy and cosmetic and functional sequelae.

Retinoblastoma: review of 30 years' experience with external beam radiotherapy

A review of the experience at the Peter MacCallum Cancer Centre (Peter Mac), Melbourne, Australia in treating retinoblastoma with external beam radiotherapy was conducted. Outcomes of particular interest were tumour control, vision preservation and treatment late effects. The review was restricted to patients that had intact eyes treated at Peter Mac from 1965 until 1997 with at least 2 years of follow up. Histories were reviewed regarding patient and tumour characteristics and treatment details. Thirty-five patients were identified in whom 47 eyes were treated. Of the tumours, 47% were Reese-Ellsworth stage IV or V and the majority of others were at high risk for vision loss because of tumour location. The radiation treatment technique became increasingly sophisticated during the study period. Radiation dose and fraction size have similarly evolved but most patients received 30-50 Gy. Since 1989, a highly accurate contact lens immobilization technique has been used to deliver 40 Gy in 20 fractions. Thirteen eyes required additional local therapy. Of the treated eyes, 34 (72%) remain intact and 74% of these have useful vision. One patient died from retinoblastoma and three from second malignant neoplasms. With modern radiotherapy, late toxicities other than growth arrest and non-progressive cataract did not occur during the study period. Tumour control was high and a very acceptable rate of organ and vision preservation was achieved in a relatively high-risk population. Modern radiotherapy continues to develop in an attempt to improve treatment accuracy and minimize late radiation toxicity.

Ocular preservation after 36 Gy external beam radiation therapy for retinoblastoma

PURPOSE

The purpose of this study was to document the ocular preservation rate after 36 Gy external beam radiation therapy (EBRT) for retinoblastoma.

PATIENTS AND METHODS

Forty-nine eyes of 38 patients were treated with a median dose of 36 Gy EBRT. The patient population included 7 unilateral and 31 bilateral presentations, with a median age at diagnosis of 4 months. Eyes enucleated at the time of diagnosis or treated with other measures were not included in the analysis of ocular preservation. The median age at EBRT was 8 months. Patients were monitored for progression of disease after EBRT and second malignant neoplasms.

RESULTS

The median follow-up was 88.6 months, with an estimated ocular preservation rate of 82.0% +/- 5% at 10 years. There was a difference in the ocular preservation rates for patients with advanced disease (Reese-Ellsworth group III-V) compared with early disease. Metastatic disease developed in two patients, and a second malignant neoplasm developed in three. Patients treated with en face electrons experienced a lower 5-year estimate of ocular preservation than those treated with photons, although patients treated with electrons were more likely to have advanced disease.

CONCLUSIONS

The use of low-dose EBRT (36 Gy) results in ocular preservation rates that are comparable to those of high-dose EBRT. The use of electrons requires careful treatment planning and computerized dosimetry.

A stereotactic radiation therapy device for retinoblastoma using a noncircular collimator and intensity filter

The proximity of the lens to the retina makes the treatment of retinoblastoma a challenge for external beam radiation therapy. The approximately 1 mm separation between the posterior edge of the lens and the anterior region of the retina causes a trade-off between coverage of the entire retina and excessive dose to the lens. A stereotactic, LINAC based, lens sparing technique for treating retinoblastoma is presented. The technique uses noncoplanar arcs with the lens at isocenter. A special noncircular collimator blocks the lens but it also causes the dose distribution to vary across the retina. A fluence modulation filter is used to reduce the dose inhomogeneity across the target. The resulting dose distribution is roughly hemispheric, providing both anterior coverage of the retina and lens blocking unlike conventional techniques. The method used to develop the collimator and filter assembly is presented. Dosimetry of the assembly was carried out using radiochromic film, and the results were entered in a treatment planning system. The dose distribution as measured in a phantom is provided and compared to calculations.

Optimized lens-sparing treatment of retinoblastoma with electron beams

PURPOSE

The ideal lens-sparing radiotherapy technique for retinoblastoma calls for 100% dose to the entire retina including the ora serrata and zero dose to the lens. Published techniques, most of which use photons, have not accomplished this ideal treatment. We describe here a technique that approaches this ideal configuration using electron beam therapy.

METHODS AND MATERIALS

Dose-modeling calculations were made using a computer program built around a proprietary algorithm. This program calculates 3D dose distribution for electrons and photons and uses the Cimmino feasibility method for the inverse problem of beam weighting to achieve the prescribed dose. The algorithm has been verified in the ocular region by measurements in a RANDO phantom. To search for an ideal lens-sparing beam setup, a stylized phantom of an 8-month-old infant was generated with built-in inhomogeneities, and a phantom of a 5-year-old child was generated from a patient CT series.

RESULTS

Of more than 100 different beam setups tested, two 9 MeV electron beams at gantry angles plus and minus 26 degrees from the optic nerve axis achieved the best distribution. Both fields have a lens block and an isocenter between the globe and origin of the optic nerve. When equal doses are given to both fields, the entire extent of the retina (including ora serrata) received 100%, while the lens received 10% or less.

CONCLUSION

The two-oblique-electron-beam technique here described appears to meet most of the stringent dosimetry needed to treat retinoblastoma. It is suitable for a range of ages, from infancy to early childhood years.

Electron/photon matched field technique for treatment of orbital disease

PURPOSE

A number of approaches have been described in the literature for irradiation of malignant and benign diseases of the orbit. Techniques described to date do not deliver a homogeneous dose to the orbital contents while sparing the cornea and lens of excessive dose. This is a result of the geometry encountered in this region and the fact that the target volume, which includes the periorbital and retroorbital tissues but excludes the cornea, anterior chamber, and lens, cannot be readily accommodated by photon beams alone. To improve the dose distribution for these treatments, we have developed a technique that combines a low-energy electron field carefully matched with modified photon fields to achieve acceptable dose coverage and uniformity.

METHODS AND MATERIALS

An anterior electron field and a lateral photon field setup is used to encompass the target volume. Modification of these fields permits accurate matching as well as conformation of the dose distribution to the orbit. A flat-surfaced wax compensator assures uniform electron penetration across the field, and a sunken lead alloy eye block prevents excessive dose to the central structures of the anterior segment. The anterior edge of the photon field is modified by broadening the penumbra using a form of pseudodynamic collimation. Direct measurements using film and ion chamber dosimetry were used to study the characteristics of the fall-off region of the electron field and the penumbra of the photon fields. From the data collected, the technique for accurate field matching and dose uniformity was generated.

RESULTS

The isodose curves produced with this treatment technique demonstrate homogeneous dose coverage of the orbit, including the paralenticular region, and sufficient dose sparing of the anterior segment. The posterior lens accumulates less than 40% of the prescribed dose, and the lateral aspect of the lens receives less than 30%. A dose variation in the match region of +/-12% is confronted when an unmodified photon field edge is matched with the fall-off of the electron field at the 50% isodose lines. By modifying the penumbra, the dose variation is reduced to +/-2%. Treatment setup accuracy is essential.

CONCLUSIONS

The electron/photon matched field technique offers a uniform isodose distribution for treatment of the orbit that has not been previously achieved. With this technique a homogeneous dose can be delivered to the entire orbit while avoiding a significant dose to the anterior segment and minimizing the risk of morbidity.

Treatment outcome and dose-response relationship in infants younger than 1 year treated for retinoblastoma with primary irradiation

Thirty-three infants ( < 1 year at diagnosis) were treated for retinoblastoma with primary irradiation at St. Jude Children's Research Hospital (SJCRH) between 1963 and June 1992. Staging of the 44 treated eyes was as follows: Reese-Ellsworth (R-E) Groups I (n = 20), Group II (n = 9), Group III (n = 6), Group IV (n = 2), Group V (n = 7). Irradiation was delivered using either a single anterior field (31 eyes) or lens-sparing techniques (13 eyes). Total doses ranged from 21-45 Gy (median = 36 Gy) in fractions of 150-180 cGy (n = 34) or > 180 cGy (n = 10). One child died of metastatic disease at 42 months. Three patients have developed second malignant neoplasms; two have succumbed at 88 and 125 months post-RB diagnosis; the remaining patients are alive at 6-259 months postdiagnosis (median follow-up = 127 months). Local control with irradiation alone and supplemented cryotherapy given within 2 months (n = 2) was maintained in 29 eyes, with no statistical difference seen for total doses < or = 36 Gy (21/8 eyes) vs. > 36 Gy (8/16). Of 15 eyes that required salvage therapy, tumor control has been maintained in 13. Enucleation was required for four patients, two with recurrent retinoblastoma and one with a phthisical eye. Cataract formation was documented in 23 eyes (87.5%) treated with lens-sparing techniques developed cataract. At last follow-up, 23 of 30 patients tested (77%) had visual acuity of 20/100 or better. This experience confirms early observations in that doses > or = 36 Gy do not appear to improve local control with irradiation alone in infants ( < 365 days) with retinoblastoma.

External beam radiation for retinoblastoma: results, patterns of failure, and a proposal for treatment guidelines

PURPOSE

To analyze treatment results and patterns of failure following external beam radiation for retinoblastoma and propose treatment guidelines according to specific clinical variables.

METHODS AND MATERIALS

We analyzed 27 patients (34 eyes) with retinoblastoma who received external beam radiation as initial treatment at Hahnemann University Hospital from October 1980 to December 1991 and have been followed for at least 1 year. Of the 34 eyes, 14 were Groups I-II (Reese-Ellsworth classification), 7 were Group III, and 13 were Groups IV-V. Doses ranged from 34.5-49.5 Gy (mean 44.3 Gy, median 45 Gy) in 1.5-2.0 Gy fractions generally delivered through anterior and lateral wedged pair fields.

RESULTS

At a mean follow up of 35.2 months (range 12-93 months), local tumor control was obtained in 44% (15 out of 34) of eyes with external beam radiation alone. Salvage therapy (plaque brachytherapy, cryotherapy, and/or photocoagulation) controlled an additional 10 eyes (29.5%), so that overall ocular survival has been 73.5%. Local tumor control with external beam radiotherapy alone was obtained in 78.5% (11 out of 14) of eyes in Groups I-II, but in only 20% (4 out of 20) of eyes in Groups III-V. A total of 67 existing tumors were identified prior to treatment in the 34 treated eyes and local control with external beam radiation alone was obtained in 87% (46 out of 53) of tumors measuring 15 mm or less and in 50% (7 out of 14) of tumors measuring more than 15 mm. When analyzing patterns of failure in the 19 eyes that relapsed, a total of 28 failure sites were identified and consisted of progression of vitreous seeds in seven instances (25% of failure sites) recurrences from previously existing tumors in 10 instances (36% of failure sites) and development of new tumors in previously uninvolved retina in 11 instances (39% of failure sites).

CONCLUSIONS

1) We find that external beam radiation to a dose of 45 Gy in fractions of 1.5 to 2.0 Gy provides adequate tumor control in retinoblastoma eyes Groups I-II (Reese-Ellsworth classification) or tumors measuring 15 mm in diameter or less. Eyes in more advanced group staging or containing tumors larger than the 15 mm seem to require higher radiation doses. We propose treatment guidelines for external beam radiation of retinoblastoma that specifically take into account the important clinical variables of tumor stage and patient age. 2) External beam radiation does not prevent the appearance of new tumors in clinically uninvolved retina. Therefore, the traditional belief that external beam radiation can treat the retina "prophylactically" should be seriously questioned. Due to this finding and their significant less morbidity, focal treatment modalities (plaque brachytherapy, photocoagulation, and/or cryotherapy), when clinically feasible, should be considered the treatment of choice for intraocular retinoblastoma. External beam radiation should be considered only when focal treatment modalities are not clinically indicated.

External beam radiation therapy and retinoblastoma: long-term results in the comparison of two techniques

PURPOSE

This study compares the long-term actuarial local control, eye conservation rate, survival, and ocular complications in children with retinoblastoma treated with two different external beam treatment techniques.

METHODS AND MATERIALS

From 1979-1991, 182 eyes in 123 children (104 bilateral) received primary external beam radiation therapy. An anterior lens-sparing electron beam technique delivering 38 to 50 Gy in 2.5 Gy fractions was used in 67 eyes from 1979-1984 and a modified lateral beam technique, delivering 42 to 46 Gy in 2 Gy fractions, was used in 113 eyes from 1984-1991. These groups were balanced with respect to known prognostic variables.

RESULTS

For Group I-III eyes, the 5- and 8-year local control was significantly improved using the modified lateral beam technique (84%) compared to (38%) using the anterior lens sparing technique (p < or = 0.0001). For Group IV-V eyes, the 5- and 8-year local control rates were not statistically different, despite a trend favoring the modified lateral beam technique. Survival endpoints including eye survival (no enucleation), cause-specific survival, and overall survival comparing the two treatment techniques were not significantly different. Overall, 22% of eyes developed cataracts. There was no difference between the two treatment groups in terms of cataract development. No eyes required enucleation for ocular complications.

CONCLUSION

There is a significant improvement in local control using the modified lateral beam technique compared to an anterior lens-sparing approach for Group I-III eyes. However, there was no difference in survival end points between the two treatment techniques. The incidence of ocular complications using these two external beam techniques is acceptable.

Ocular globe topography in radiotherapy

PURPOSE

Ocular lens, retina, and olfactory bulb exposure are common concerns in contemporary radiotherapy practice. Methods to clinically localize soft tissue structures (i.e., lens and retina) are varied and often imprecise. We hypothesized that eyelid markers constituted a better reference point than the commonly used lateral canthus marker for lateral beam simulations, unless diagnostic computed tomography or ultrasound examinations were available and/or used.

METHODS AND MATERIALS

Sixty-six pre-Magnetic Resonance Image, normal, orbital computed tomography scans from adult patients were used to measure (a) sagittal distances from eyelid to posterior lens surface, from lateral canthus to posterior lens surface and to the globe's posterior pole, (b) supero-inferior distances in the lateral projection from the lens to the cribriform plate, and (c) common dimensions to establish internal validity of the measurements.

RESULTS

The eyelid to lens and retina topography is individually more constant than that from the canthus. There is little if any supero-inferior separation between the lens and the cribriform plate lateral projections.

CONCLUSIONS

The lateral canthus does not specify lens or retina locations. Eyelid markers of known size provide more accurate anatomical information. Lateral beam ocular globe shielding has to be individualized. Lens shielding is questionable if the olfactory bulb needs to be irradiated by a lateral beam.

Use of irradiation for therapy of retinoblastoma in children more than 1 year old: the St. Jude Children's Research Hospital experience and review of literature

Fifteen children (> 1 year old at diagnosis) were treated for retinoblastoma (RB) with primary irradiation at St. Jude Children's Research Hospital between January 1963 and January 1992. Staging of the 19 treated eyes was as follows: Reese-Ellsworth (R-E) Groups I and II, n = 7; Group III, n = 3; Group IV, n = 1; Group V, n = 7; information on one globe is incomplete. Total dosage ranged from 25 to 45 Gy (median = 40 Gy) in fractions of 170-225 cGy delivered 5 x/week (n = 13) or 225-265 cGy delivered 4 x/week (n = 4 eyes) or x 5/week (n = 2 eyes). Treatment techniques included anterior field (n = 11) or lens-sparing technique (n = 8). One patient has died of progressive central nervous system (CNS) disease at 13 months; one patient succumbed to second malignant neoplasm within the irradiated field at 194 months; the remaining 13 patients remain alive from 27 to 301 months (median = 178 months). Local control with irradiation alone has been maintained in 12 eyes. Four eyes with local recurrence were salvaged using cryotherapy or reirradiation. Enucleation was required for three eyes for progressive disease at 4, 7, and 7 months postirradiation. Cataract formation was documented in nine eyes treated with anterior fields and in one patient treated with lens-sparing technique. At last follow-up, 7 patients had visual acuity of 20/100 or better. Radiation dose of 40 Gy appears to be adequate for local control of early stage RB (R-E Groups I-III and VB whose tumors are R-E Groups I-III) in patients > 1 year old. The results of this limited series which has lengthy follow-up is compared with the results of previously published data in an effort to define the benefits and disadvantages of the different treatment techniques which have been reported in the treatment of RB in children > 1 year old.

External beam radiotherapy for retinoblastoma: II. Lens sparing technique

A retrospective analysis is presented of the results of external beam radiotherapy for retinoblastoma utilising an accurate lens sparing technique. Local tumour control has been assessed in a consecutive series of 67 eyes in 53 children all of whom received external beam radiotherapy as the primary treatment of retinoblastoma. Follow up ranged from 12 to 82 months (median 35 months) with 76% of the children followed for more than 2 years. Tumour control rates have been analysed with respect to the Reese-Ellsworth classification. The role of adjuvant and salvage focal therapy is emphasised. Following lens sparing radiotherapy with prior adjuvant treatment of anterior tumours, where appropriate, the overall ocular cure rate was 72%. With salvage therapy of persistent, recurrent, or new tumours, 93% of eyes could be preserved in this series which includes mainly eyes classified in Reese-Ellsworth groups I-III. These results compare favourably with those of whole eye external beam radiotherapy for comparable tumours, and with those of lens and anterior segment sparing using other techniques. They were achieved without the ocular morbidity associated with whole eye external beam radiotherapy.

External beam radiotherapy for retinoblastoma: I. Whole eye technique

A retrospective analysis has been performed of the results of external beam radiotherapy for retinoblastoma using a whole eye technique. Local tumour control has been assessed in a consecutive series of 175 eyes in 142 children all of whom received external beam radiotherapy as the primary treatment for retinoblastoma. Follow up ranged from 2 to 17 years (median 9 years). Tumour control rates have been analysed with respect to the Reese Ellsworth classification and the series includes eyes in groups I to V. Focal salvage therapy was given for persistent, recurrent, or new tumours after radiotherapy. Following whole eye radiotherapy alone, the overall ocular cure rate was 57%, though with salvage therapy 80% of eyes could be preserved.

Three-dimensional treatment planning for maxillary cancer using a CT simulator

PURPOSE

The results of three-dimensional treatment planning using a computed tomography simulator were evaluated in patients with maxillary cancer.

METHODS AND MATERIALS

Treatment planning was done in 25 patients using an x-ray simulator and plain x-ray films (1979-1982, group 1) in 34 patients using an x-ray simulator and computed tomography films (1983-1987, group 2), in 24 patients using a computed tomography simulator (1988-1992, group 3). The number of patients with Stage IV disease increased in the order of group 1 to group 3.

RESULTS

The average radiation field was smallest in group 3 (66.5 cm2) followed by group 2 (67.4 cm2) and group 1 (72.9 cm2). A radiation dose of more than 30 Gy to the lens of the effected side was delivered to 13% of group 3, 44% of group 2, and 44% of group 1. The dose to the lens on the uneffected side was zero in 56% of group 1, 74% of group 2, and 96% of group 3. A long-term decrease in visual activity on the effected side occurred in 11% of group 3, 32% of group 2, and 44% of group 1. However, a significant increase in survival was only noted between groups 1 and 2, because the three population of patients were different.

CONCLUSION

The three-dimensional treatment planning results in a better treatment than two-dimensional treatment planning as measured by complication rates and field sizes.

Hypofractionation in retinoblastoma: an increased risk of retinopathy

Forty-four eyes in 38 children were treated between 1963 and 1991 by external radiotherapy for retinoblastoma. Treatment modalities varied widely during this period; in addition to radiotherapy there was chemotherapy (16/44), photocoagulation (14/44), and laser therapy or cryotherapy (14/44). Treatment technique and dose fractionation also varied widely; lateral beam technique (39/44) versus anterior or anterior/lateral beam; doses per fraction ranged from 1 to 4.5 Gy, total doses from 30 to 61.5 Gy, and overall times from 22 to 49 days. Patients were followed at 3-month intervals, and actuarial survival at 10 years was 88%, with 62% local control. Ten eyes showed clinical evidence of retinopathy. A multivariate analysis of factors associated with increased risk of retinopathy was carried out using the Cox proportional hazards model and the mixture model of Farewell. The estimated latent time was 17 months (95% confidence interval, 14-20 months). The only factors found to be significantly associated with retinopathy were total dose multiplied by dose per fraction, or total dose normalized to the equivalent total dose in 2-Gy fractions as estimated from the LQ model, and these gave equivalent descriptions. There were trends (not significant) for increased risk of retinopathy when treatments included chemotherapy or photocoagulation, and for decreased risk (also not significant) when cryotherapy was used in conjunction with radiotherapy. No significance could be attached to any of the following: number of sites per eye, Reese-Ellsworth stage, and family history. We conclude that hypofractionation carries a significant risk for retinopathy in the treatment of retinoblastoma.

A unique case of retinoblastoma masked by retinal detachment diagnosis and management

A 4-year-old Latin American boy presented with a history of loss of vision of his left eye for 7 months. He was followed by different ophthalmologists and diagnosed with a retinal detachment. Computerized tomograms and magnetic resonance imaging demonstrated a large calcified left eye and markedly enlarged optic nerve. Based on these radiologic findings diagnosis of retinoblastoma was strongly suspected. Initially enucleation was not done because it was thought that cutting through the involved optic nerve would cause dissemination. The patient was treated with chemotherapy which resulted in marked response. Following normalization of optic nerve and after irradiation the eye was enucleated. The diagnosis of retinoblastoma was confirmed. No tumor was found in the optic nerve. The importance of imaging studies in diagnosis of retinoblastoma and the role of chemotherapy in the treatment of primary retinoblastoma are emphasized.

Local control and complications after radiation therapy for primary orbital lymphoma: a case for low-dose treatment

Orbital involvement at the time of initial presentation is unusual in non-Hodgkin's lymphoma. In an effort to identify potential ways of improving the radiotherapeutic management of this disease, the records of 22 patients were reviewed retrospectively. All had biopsy-proven orbital non-Hodgkin's lymphoma, and the minimal, median, and maximal durations of follow-up in surviving patients were 4.8 years, 7.0 years, and 17.4 years, respectively. Permanent local control was achieved in 21 of the 22 patients (96%). Complications were scored according to a grading scheme in which grade 1 was the least significant complication and grade 4 was blindness as a result of radiation therapy. Of the 12 patients who received a radiation dose less than 35 Gy, 6 developed a grade 1 or grade 2 complication. Of the 10 patients treated with greater than or equal to 35 Gy, 6 experienced a complication, 1 of whom had a grade 4 complication resulting in blindness and another who developed a severe keratitis, which was scored as a grade 3 complication resulting in decreased visual acuity. At last follow-up, 10 patients were alive at 4.8 to 17.4 years after completion of radiation therapy, 4 had died of intercurrent disease at 3 months to 10.6 years, and 8 had died of disease at 3 months to 15.8 years. Actuarial survival for the entire group was 75% at 5 years and 48% at 10 years. Survival in patients with Stage I AE disease (lymphoma confined to orbit) at presentation was 87% at 5 years and 50% at 10 years, and survival in patients with Stage II A through Stage IV disease was 36% at 5 years and at 10 years. Primary orbital lymphoma is an indolent disease characterized by prolonged survival after radiation therapy. Excellent local control can be achieved with radiation doses of 20 Gy to 35 Gy. Higher doses may result in an increased risk of complications.

Study of dose perturbation parameters for eye shielding in megavoltage photon beam therapy

Shielding blocks are frequently used to minimize dose and shield sensitive organs in radiation therapy. The blocks, which are made of high atomic number materials, produce significant dose perturbations in megavoltage photon beams. The effects of these perturbations are studied with special interest in the eye shielding in the treatment of head and neck malignancies. Optimum parameters for the treatment are suggested.