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

Comparison of dosimetric parameters for predicting radiation-induced cataract in paediatric patients

INTRODUCTION

This study compared the predictive ability of radiation-induced cataract between maximum point dose of the lens (Lens Dmax) ≥7 Gy, mean lens dose (Lens Dmean) ≥7 Gy, Lens Dmax ≥10 Gy, and Lens Dmean ≥10 Gy.

METHODS

Patients aged 3-18 years received cranial irradiation or radiation therapy at head and neck area between January 2010 and December 2019 at our institute were included. Patients without baseline and/or follow-up eye examination were excluded. Receiver operating characteristic (ROC) curves identified potential predictors and Cox regression analysed correlations between potential factors and cataract occurrence.

RESULTS

Sixty-three patients (122 eyes) were analysed. Cataracts were detected in 14 eyes (11.5%). Median follow-up time was 4 years (range 0.5-10 years), with cataract developing in a median of 2.5 years (range 0.3-7 years). Three patients (21.4%) developed grade ≥3 cataract. Lens Dmean ≥10 Gy was associated with cataract formation.

CONCLUSION

Lens Dmean ≥10 Gy showed the highest ability for predicting radiation-induced cataract in paediatric patients. Net reclassification improvement (NRI) suggested that changing lens dose constraint from Dmax <7 Gy to Dmean <10 Gy would miss 7% of cataract cases but avoid 28% of unnecessary restrictions. Adopting a mean lens dose <10 Gy was suggested as a constraint for lens dose.

Retinopathy, Optic Neuropathy, and Cataract in Childhood Cancer Survivors Treated With Radiation Therapy: A PENTEC Comprehensive Review

PURPOSE

Few reports describe the risks of late ocular toxicities after radiation therapy (RT) for childhood cancers despite their effect on quality of life. The Pediatric Normal Tissue Effects in the Clinic (PENTEC) ocular task force aims to quantify the radiation dose dependence of select late ocular adverse effects. Here, we report results concerning retinopathy, optic neuropathy, and cataract in childhood cancer survivors who received cranial RT.

METHODS AND MATERIALS

A systematic literature search was performed using the PubMed, MEDLINE, and Cochrane Library databases for peer-reviewed studies published from 1980 to 2021 related to childhood cancer, RT, and ocular endpoints including dry eye, keratitis/corneal injury, conjunctival injury, cataract, retinopathy, and optic neuropathy. This initial search yielded abstracts for 2947 references, 269 of which were selected as potentially having useful outcomes and RT data. Data permitting, treatment and outcome data were used to generate normal tissue complication probability models.

RESULTS

We identified sufficient RT data to generate normal tissue complication probability models for 3 endpoints: retinopathy, optic neuropathy, and cataract formation. Based on limited data, the model for development of retinopathy suggests 5% and 50% risk of toxicity at 42 and 62 Gy, respectively. The model for development of optic neuropathy suggests 5% and 50% risk of toxicity at 57 and 64 Gy, respectively. More extensive data were available to evaluate the risk of cataract, separated into self-reported versus ophthalmologist-diagnosed cataract. The models suggest 5% and 50% risk of self-reported cataract at 12 and >40 Gy, respectively, and 50% risk of ophthalmologist-diagnosed cataract at 9 Gy (>5% long-term risk at 0 Gy in patients treated with chemotherapy only).

CONCLUSIONS

Radiation dose effects in the eye are inadequately studied in the pediatric population. Based on limited published data, this PENTEC comprehensive review establishes relationships between RT dose and subsequent risks of retinopathy, optic neuropathy, and cataract formation.

Physics Considerations for Evaluation of Dose for Dose-Response Models of Pediatric Late Effects From Radiation Therapy: A PENTEC Introductory Review

PURPOSE

We describe the methods used to estimate the accuracy of dosimetric data found in literature sources used to construct the Pediatric Normal Tissue Effects in the Clinic (PENTEC) dose-response models, summarize these findings of each organ-specific task force, describe some of the dosimetric challenges and the extent to which these efforts affected the final modeling results, and provide guidance on the interpretation of the dose-response results given the various dosimetric uncertainties.

METHODS AND MATERIALS

Each of the PENTEC task force medical physicists reviewed all the journal articles used for dose-response modeling to identify, categorize, and quantify dosimetric uncertainties. These uncertainties fell into 6 broad categories. A uniform nomenclature was developed for describing the "dosimetric quality" of the articles used in the PENTEC reviews. Among the multidisciplinary experts in the PENTEC effort, the medical physicists were charged with the dosimetric evaluation, as they are most expert in this subject.

RESULTS

The percentage dosimetric uncertainty was estimated for each late effect endpoint for all PENTEC organ reports. Twelve specific sources of dose uncertainty were identified related to the 6 broad categories. The most common reason for organ dose uncertainty was that prescribed dose rather than organ dose was reported. Percentage dose uncertainties ranged from 5% to 200%. Systematic uncertainties were used to correct the dose component of the models. Random uncertainties were also described in each report and in some cases used to modify dose axis error bars. In addition, the potential effects of dose binning were described.

CONCLUSIONS

PENTEC reports are designed to provide guidance to radiation oncologists and treatment planners for organ dose constraints. It is critical that these dose constraint recommendations are as accurate as possible, acknowledging the large error bars for many. Achieving this accuracy is important as it enables clinicians to better balance target dose coverage with risk of late effects. Evidence-based dose constraints for pediatric patients have been lacking and, in this regard, PENTEC fills an important unmet need. One must be aware of the limitations of our recommendations, and that for some organ systems, large uncertainties exist in the dose-response model because of clinical endpoint uncertainty, dosimetric uncertainty, or both.

Risk factors for cataract in retinoblastoma management

AIMS

To investigate the risk factors for cataract following eye-preserving therapies for retinoblastoma.

METHODS

This retrospective, single-centre cohort study included patients diagnosed with retinoblastoma receiving eye-preserving therapies between January 2017 and June 2021. Cataract by the end of the follow-up was the main outcome.

RESULTS

Cataract was found in 31 of 184 (16.8%) included eyes during a mean follow-up of 27.6 months. The cataract and control groups were similar regarding patients' laterality, sex and disease stage. Eyes in the cataract group were more likely to present with endophytic retinoblastoma (p=0.02) and greater intraocular pressure (p=0.001). Competing risk regression analysis (univariate Fine-Gray model) showed that the growth pattern (p=0.01), intraocular pressure (p=0.01), number of intra-arterial chemotherapy (IAC) cycles (p=0.001), melphalan dose per IAC cycle (p=0.001) and number of intravitreous chemotherapy (IvitC) cycles (p=0.001) were associated with cataract occurrence. Multivariate analysis included higher intraocular pressure (p=0.003), a higher melphalan dose per IAC cycle (p=0.001) and an increasing number of IvitC cycles (p=0.04) as independent risk factors for cataract.

CONCLUSIONS

Repeated IAC and/or IvitC with melphalan were the most common eye-preserving therapies that induced cataract formation. The toxic effect of melphalan was an essential factor in cataract development, as indicated by the association of cataract occurrence with the melphalan dose.

Dosimetric comparison of pencil beam scanning proton therapy with or without multi-leaf collimator versus volumetric-modulated arc therapy for treatment of malignant glioma

This study aimed to examine the dosimetric effect of intensity-modulated proton therapy (IMPT) with a multi-leaf collimator (MLC) in treating malignant glioma. We compared the dose distribution of IMPT with or without MLC (IMPT_MLC+ or IMPT_MLC-, respectively) using pencil beam scanning and volumetric-modulated arc therapy (VMAT) in simultaneous integrated boost (SIB) plans for 16 patients with malignant gliomas. High- and low-risk target volumes were assessed using D_2%, V_90%, V_95%, homogeneity index (HI), and conformity index (CI). Organs at risk (OARs) were evaluated using the average dose (D_mean) and D_2%. Furthermore, the dose to the normal brain was evaluated using from V_5Gy to V_40Gy at 5 Gy intervals. There were no significant differences among all techniques regarding V_90%, V_95%, and CI for the targets. HI and D_2% for IMPT_MLC+ and IMPT_MLC- were significantly superior to those for VMAT (p < 0.01). The D_mean and D_2% of all OARs for IMPT_MLC+ were equivalent or superior to those of other techniques. Regarding the normal brain, there was no significant difference in V_40Gy among all techniques whereas V_5Gy to V_35Gy in IMPT_MLC+ were significantly smaller than those in IMPT_MLC- (with differences ranging from 0.45% to 4.80%, p < 0.05) and VMAT (with differences ranging from 6.85% to 57.94%, p < 0.01). IMPT_MLC+ could reduce the dose to OARs, while maintaining target coverage compared to IMPT_MLC- and VMAT in treating malignant glioma.

Presence of cataract in patients treated for retinoblastoma at the national institute of pediatrics in Mexico (2011-2021)

PURPOSE

The goal of this study is to describe the presence of secondary cataract in patients with retinoblastoma treated at the National Institute of Pediatrics of Mexico (INP) over the past 10 years.

METHODS

This was a single center observational, retrospective and descriptive study. We included all eyes diagnosed with retinoblastoma and cataract between June 2011 and June 2021.

RESULTS

In total, 833 records of patients diagnosed with Retinoblastoma at the National Institute of Pediatrics during the period between June 2011 and June 2021 were reviewed. Out of all of them, only 14 developed cataract (1.6%). The median age at retinoblastoma diagnosis was 10.5 months (Rank: 6-13 months), and the median age at cataract diagnosis was 51.5 months (Rank: 25-73 months). The majority (13, 92.9%) of the patients had bilateral involvement. 42% of the eyes were Stage D according to the international classification of retinoblastoma. Cryotherapy was applied in 57.1%, intravitreal chemotherapy in 85.7%, radiation therapy in 42.6%, and only 7.1% of cases were treated with intra-arterial chemotherapy.

CONCLUSIONS

The presence of cataract in patients with retinoblastoma is a rare but important entity impacting the development of vision in children and detection of intraocular tumors. These probably occur late as a result of the multiple treatments to which the children have been subjected, without being able to determine in this study which is the risk factor most associated with the development of this pathology.

Analysis of dose to the macula, optic disc, and lens in relation to vision toxicities - A retrospective study using COMS eye plaques

PURPOSE

The aim of this study was to relate common toxicity endpoints with dose to the macula, optic disc, and lens for uveal melanoma patients treated with Iodine-125 Collaborative Ocular Melanoma Study (COMS) eye plaque brachytherapy.

METHODS

A cohort of 52 patients treated at a single institution between 2005 and 2019 were retrospectively reviewed. Demographics, dosimetry, and clinical outcomes were recorded. Univariate, relative risk, and Kaplan-Meier analyses were performed to relate dose to toxicity endpoints including retinopathy, vision decline, and cataracts.

RESULTS

By the end of follow up (Median = 3.6 years, Range = 0.4 - 13.5 years), 65 % of eyes sustained radiation retinopathy, 40 % demonstrated moderate vision decline (>5 Snellen lines lost), and 56 % developed cataracts. Significant (p < 0.05) risk estimates exist for retinopathy and VA decline for doses >52 Gy to the macula and >42 Gy to the optic disc. Moreover, dose to the lens > 16 Gy showed a significant risk for cataract formation. Kaplan-Meier analysis demonstrated significantly different incidence of radiation retinopathy for > 52 Gy to the macula and > 42 Gy to the optic disc. In addition, the Kaplan-Meier analysis showed significantly different incidence of cataract formation for patients with lens dose > 16 Gy.

CONCLUSIONS

Dose-effect relationships exist for the macula and optic disc with respect to the loss of visual acuity and the development of retinopathy. To better preserve vision after treatment, further research is needed to reduce macula, optic disc, and lens doses while maintaining tumor control.

Pediatric Cataract Surgery Following Treatment for Retinoblastoma: A Case Series and Systematic Review

PURPOSE

To determine the visual and refractive outcomes and the ocular and systemic complications of cataract surgery in eyes treated for retinoblastoma.

DESIGN

Retrospective consecutive case series and systematic review.

METHODS

Children <18 years of age with retinoblastoma who underwent surgery for secondary cataract between 2000 and 2020 were reviewed. Medline (OVID), Embase, Web of Science, and the Cochrane database were searched from inception to August 2020.

RESULTS

A total of 15 eyes of 15 children were included. The mean age at retinoblastoma diagnosis was 12 months (median, 14; interquartile range [IQR], 4-19). Cataract developed at a mean age of 39 months (median, 31; IQR, 20-52), secondary to multiple treatments (n = 7), pars-plana vitrectomy (n = 3), external-beam radiotherapy (n = 2), laser (n = 2), and retinal detachment (n = 1). The mean preoperative quiescent interval was 44 months (median, 28; IQR, 15-64). Primary intraocular lens implantation was performed in 93%, posterior capsulotomy in 40%, and anterior vitrectomy in 33% of participants. Postoperatively, 100% had improved fundus visibility and 73% had improved vision. Complications included visual axis opacification (11 of 15), capsular phimosis (5 of 15), and zonulopathy (3 of 15). No patient developed intraocular recurrence, extraocular extension, or metastasis at a mean of 76 months (median, 78; IQR, 29-128) follow-up. The systematic review identified 852 studies, with 18 meeting inclusion criteria. Across all studies (n = 220 children), intraocular recurrence occurred in 6%, globe salvage in 91%, and extraocular extension and metastasis in <1%.

CONCLUSIONS

Modern retinoblastoma therapies, including intravitreal chemotherapy and vitrectomy, cause secondary cataract. Following cataract surgery, intraocular recurrence risk is low and extraocular spread is rare. Although surgery improves tumor visualization, visual prognosis may be limited by several factors. Challenges include biometry limitations and a high incidence of zonulopathy.

Influence of eye movement on lens dose and optic nerve target coverage during craniospinal irradiation

Purpose

Optic nerves are part of the craniospinal irradiation (CSI) target volume. Modern radiotherapy techniques achieve highly conformal target doses while avoiding organs-at-risk such as the lens. The magnitude of eye movement and its influence on CSI target- and avoidance volumes are unclear. We aimed to evaluate the movement-range of lenses and optic nerves and its influence on dose distribution of several planning techniques.

Methods

Ten volunteers underwent MRI scans in various gaze directions (neutral, left, right, cranial, caudal). Lenses, orbital optic nerves, optic discs and CSI target volumes were delineated. 36-Gy cranial irradiation plans were constructed on synthetic CT images in neutral gaze, with Volumetric Modulated Arc Therapy, pencil-beam scanning proton therapy, and 3D-conventional photons. Movement-amplitudes of lenses and optic discs were analyzed, and influence of gaze direction on lens and orbital optic nerve dose distribution.

Results

Mean eye structures' shift from neutral position was greatest in caudal gaze; -5.8±1.2 mm (±SD) for lenses and 7.0±2.0 mm for optic discs. In 3D-conventional plans, caudal gaze decreased Mean Lens Dose (MLD). In VMAT and proton plans, eye movements mainly increased MLD and diminished D98 orbital optic nerve (D98_OON) coverage; mean MLD increased up to 5.5 Gy [total ΔMLD range -8.1 to 10.0 Gy], and mean D98_OON decreased up to 3.3 Gy [total ΔD98_OON range -13.6 to 1.2 Gy]. VMAT plans optimized for optic disc Internal Target Volume and lens Planning organ-at-Risk Volume resulted in higher MLD over gaze directions. D98_OON became ≥95% of prescribed dose over 95/100 evaluated gaze directions, while all-gaze bilateral D98_OON significantly changed in 1 of 10 volunteers.

Conclusion

With modern CSI techniques, eye movements result in higher lens doses and a mean detriment for orbital optic nerve dose coverage of <10% of prescribed dose.

Radiation therapy-associated toxicity: Etiology, management, and prevention

Radiation therapy (RT) is a curative treatment for many malignancies and provides effective palliation in patients with tumor-related symptoms. However, the biophysical effects of RT are not specific to tumor cells and may produce toxicity due to exposure of surrounding organs and tissues. In this article, the authors review the clinical context, pathophysiology, risk factors, presentation, and management of RT side effects in each human organ system. Ionizing radiation works by producing DNA damage leading to tumor death, but effects on normal tissue may result in acute and/or late toxicity. The manifestation of toxicity depends on both cellular characteristics and affected organs' anatomy and physiology. There is usually a direct relationship between the radiation dose and volume to normal tissues and the risk of toxicity, which has led to guidelines and recommended dose limits for most tissues. Side effects are multifactorial, with contributions from baseline patient characteristics and other oncologic treatments. Technological advances in recent decades have decreased RT toxicity by dramatically improving the ability to deliver RT that maximizes tumor dose and minimizes organ dose. Thus the study of RT-associated toxicity is a complex, core component of radiation oncology training that continues to evolve alongside advances in cancer management. Because RT is used in up to one-half of all patients with cancer, an understanding of its acute and late effects in different organ systems is clinically pertinent to both oncologists and nononcologists.

Lens dose to standing patients treated with electrons to the hand

Patients receiving radiotherapy to the hand are sometimes treated standing, with their heads beside and potentially facing an electron applicator. This raises the possibility of consequential lens dose from scattered electrons, which this study investigates. This study measures the dose beside an applicator at a depth of 3 mm in a phantom as an estimate of lens dose for such patients. The lens dose is investigated as a function of height, distance, beam energy, applicator size, and cutout fill on a Varian Trilogy linear accelerator. The effect of the potential mitigation strategies of turning the head or shielding with lead sheets is also investigated. Measurement found that a typical hand setup may result in the lens receiving 0.15% of the treatment dose, which would deliver a cumulative dose above the demonstrated threshold dose for cataract risk for some courses. Large applicators and close facial proximity to the applicator separately enhance dose by factors of 3 and 5 respectively, raising the possibility of multiple gray to the lens for patients in unfavorable setups. Simple and effective mitigation strategies are available: Turning the patient's head to the side or placing 1-2 mm of lead on glasses reduced lens dose by a factor of 3-4, and covering the side of the applicator with 1 mm of lead or turning the head completely away effectively eliminated lens dose. The lens dose can be consequential but is readily mitigated.

Bilateral retinal detachment after chimeric antigen receptor T-cell therapy

CAR T-cell targeting of leukemic infiltrates in the optic nerve and retina caused retinal detachment as a presentation of pseudoprogression. Treatment of this intraocular inflammation with intravitreal triamcinolone and orbital radiation led to marked improvement in visual acuity.

Rare tumors: Retinoblastoma, nasopharyngeal cancer, and adrenocorticoid tumors

The role of surgery, chemotherapy, and radiation therapy for retinoblastoma has evolved considerably over the years with the efficacy of intraarterial chemotherapy and the high incidence of secondary malignant neoplasms following radiation therapy. The use of spot scanning intensity-modulated proton therapy may reduce the risk of secondary malignancies. For pediatric nasopharyngeal carcinoma, the current standard of care is induction chemotherapy followed by chemoradiation therapy. For adrenocortical carcinoma, the mainstay of treatment is surgery and chemotherapy. The role of radiation therapy remains to be defined.

Radiation-induced lens opacities: Epidemiological, clinical and experimental evidence, methodological issues, research gaps and strategy

In 2011, the International Commission on Radiological Protection (ICRP) recommended reducing the occupational equivalent dose limit for the lens of the eye from 150 mSv/year to 20 mSv/year, averaged over five years, with no single year exceeding 50 mSv. With this recommendation, several important assumptions were made, such as lack of dose rate effect, classification of cataracts as a tissue reaction with a dose threshold at 0.5 Gy, and progression of minor opacities into vision-impairing cataracts. However, although new dose thresholds and occupational dose limits have been set for radiation-induced cataract, ICRP clearly states that the recommendations are chiefly based on epidemiological evidence because there are a very small number of studies that provide explicit biological and mechanistic evidence at doses under 2 Gy. Since the release of the 2011 ICRP statement, the Multidisciplinary European Low Dose Initiative (MELODI) supported in April 2019 a scientific workshop that aimed to review epidemiological, clinical and biological evidence for radiation-induced cataracts. The purpose of this article is to present and discuss recent related epidemiological and clinical studies, ophthalmic examination techniques, biological and mechanistic knowledge, and to identify research gaps, towards the implementation of a research strategy for future studies on radiation-induced lens opacities. The authors recommend particularly to study the effect of ionizing radiation on the lens in the context of the wider, systemic effects, including in the retina, brain and other organs, and as such cataract is recommended to be studied as part of larger scale programs focused on multiple radiation health effects.

Phase I dose-escalation trial of S-1 combined with carbon-ion radiotherapy for sinonasal squamous cell carcinoma

This study aimed to determine the maximum tolerance dose (MTD) and to estimate the recommended dose (RD) of concomitant S-1 with carbon-ion radiotherapy (RT) for sinonasal squamous cell carcinoma (SCC). Nine patients with sinonasal SCC received carbon-ion RT with escalating doses of S-1 according to phase I methods. Doses of 40, 60 and 80 mg/m2/day were administered twice daily in dose levels 1, 2 and 3, respectively, from days 1 to 14 and 22 to 35. Carbon-ion RT was administered at a dose of 70.4 Gy (relative biological effectiveness) in 32 fractions, 5 days a week. Two patients developed grade 3 acute dermatitis. However, none developed dose-limiting toxicities. Therefore, the MTD of S-1 could not be determined; the RD was estimated to be 80 mg/m2/day with concurrent carbon-ion RT. Partial response and stable disease were noted in 5 and 4 patients, respectively. The 2-year overall survival and local control rates were 56 and 74%, respectively. Overall, 2 patients developed ≥grade 3 late toxicities; among them, 1 patient developed grade 3 cataract and the other developed grade 4 cataract, optic nerve disorder and hearing impairment. To the best of our knowledge, this phase I study is the first clinical trial to evaluate concomitant S-1 with carbon-ion RT for sinonasal SCC. The MTD of S-1 could not be determined, and the RD was estimated to be 80 mg/m2/day. This study demonstrated a manageable safety profile for this combination. The observed outcomes may facilitate further evaluation of this novel therapy.

45 GyRBE for group III orbital embryonal rhabdomyosarcoma

Purpose: Despite widespread concerns of radiotherapy toxicity in children with head and neck tumors, recent Children's Oncology Group (COG) findings suggest that the use of 45 Gy results in an unacceptably high rate of local recurrences in patients with low-risk orbital rhabdomyosarcoma. We therefore evaluated outcomes in our pediatric patients who received 45 GyRBE using proton therapy. Material and methods: To assess disease control and toxicity, we reviewed the medical records of 30 children (≤21 years old) with COG stage 1, group III embryonal orbital rhabdomyosarcoma enrolled on a prospective outcome study and treated with proton therapy between 2007 and 2018. Results: Median age at the time of radiation was 4.8 years old. Twenty-one and nine patients received ifosfamide- and cyclophosphamide-based chemotherapy according to their respective cooperative group regimens. Median duration between the start of induction chemotherapy and radiation was 12 weeks. Two patients had a complete response to induction chemotherapy and two had stable disease. Twenty-six patients had a partial response to induction chemotherapy, with a median volume reduction of 66%. With a median follow-up of 4.0 years (range, 0.5-9.5 years), we observed 1 local failure 6 months following treatment in a patient who had a partial response to cyclosphophomide-based induction chemotherapy. The 5-year local control, progression-free survival, and overall survival rates were 97%, 97%, and 100%, respectively. Serious late toxicities included 18 patients with cataracts, 4 with exposure keratoconjunctivitis resulting in permanently reduced visual acuity, and 1 with chronic sinusitis. Conclusion: 45 GyRBE offers effective local control for most patients with group III orbital rhabdomyosarcoma. The delivery of proton therapy to the postinduction tumor volume plus a small margin can mitigate early- and intermediate-term toxicity, but side effects still occur and long-term data are needed to demonstrate the dosimetric advantage of proton therapy.