Ruthenium-106 plaque radiotherapy for uveal melanoma: analysis of tumor dimension and location on anatomical and functional results

Apical dose versus volume dose of Ruthenium-106 brachytherapy for uveal melanoma

OBJECTIVE

Ruthenium-106 brachytherapy is commonly used to treat uveal melanomas. Most centres prescribe a radiation dose to the tumour apex that is calculated with the tumour located in the centre of the plaque. Recent work suggests that D99%-the minimum radiation dose delivered to 99% of tumour volume-may be a better predictor of tumour control than apex dose. Both dosing regimens may be affected by tumour and treatment variables differently. We explored the effect of differences in these variables on volume and apex dose using a 3-dimensional planning model.

METHODS

The time required to deliver 100 Gy to the tumour apices of representative tumours ranging from 2- to 6-mm thickness with central plaque positioning was calculated in Plaque Simulator™. This treatment time was used for further calculations, including D99% with central plaque placement, and apical and tumour volume doses when tumour and plaque characteristics were altered, including eccentric plaque placement, either away from (tilt) or along (offset) scleral surface, tumour shape, and plaque type.

RESULTS

D99% was always greater than the apex dose when plaques were placed centrally, and the difference increased with tumour thickness. Increasing degrees of tumour offset reduced apical dose and D99%, with a greater effect on apical dose for thicker and D99% for thinner tumours, respectively. Differences in tumour shape and plaque type had idiosyncratic effects on apical and volume dosing.

CONCLUSION

D99% and apex dose are affected by tumour and treatment characteristics in different ways, highlighting the complexity of radiation delivery to uveal tumours.

From Molecular Biology to Novel Immunotherapies and Nanomedicine in Uveal Melanoma

Molecular biology studies of uveal melanoma have resulted in the development of novel immunotherapy approaches including tebentafusp-a T cell-redirecting bispecific fusion protein. More biomarkers are currently being studied. As a result, combined immunotherapy is being developed as well as immunotherapy with bifunctional checkpoint inhibitory T cell engagers and natural killer cells. Current trials cover tumor-infiltrating lymphocytes (TIL), vaccination with IKKb-matured dendritic cells, or autologous dendritic cells loaded with autologous tumor RNA. Another potential approach to treat UM could be based on T cell receptor engineering rather than antibody modification. Immune-mobilizing monoclonal T cell receptors (TCR) against cancer, called ImmTAC TM molecules, represent such an approach. Moreover, nanomedicine, especially miRNA approaches, are promising for future trials. Finally, theranostic radiopharmaceuticals enabling diagnosis and therapy with the same molecule bring hope to this research.

Incidence, risk factors and outcomes of cataract surgery after plaque brachytherapy for posterior uveal melanoma

Purpose

To examine incidence, risk factors, and outcomes of cataract surgery after plaque brachytherapy for posterior uveal melanoma.

Design

Retrospective interventional cohort study contrasted with general population data.

Methods

All patients treated with plaque brachytherapy for a posterior uveal melanoma at Sweden's national referral center between 2010 and 2022 were included (n = 933). These patients were cross-referenced with data from the Swedish National Cataract Register. Competing risk incidences and outcomes of cataract surgery were compared with a random sample of 1000 individuals from the general population.

Results

The 12-year incidence of cataract surgery after plaque brachytherapy was 27 % (95 % CI 23-31 %), which markedly exceeded the incidence of 16 % in the general population (95 % CI 13-18 %, Gray's P < 0.001). Patients treated with Iodine-125 had significantly higher incidence than patients treated with Ruthenium-106, and the latter had greater incidence than the general population (P < 0.001). In univariate competing risk regressions, older patients, female sex, thick tumors, and Iodine-125 were associated with cataract surgery. In multivariate analysis, older patients and Iodine-125 retained their significance. Outcomes of cataract surgery were overall similar in the plaque brachytherapy and general population, but the general population more often received post op. topical NSAID.

Conclusions

In this study, plaque brachytherapy for posterior uveal melanoma was associated with a significantly increased incidence of cataract surgery. Treatment with the gamma emitting isotope iodine-125 and older patient age at the time of brachytherapy emerged as the major risk factors. Outcomes of cataract surgery were comparable to the general population.

Brachytherapy With 15- Versus 20-mm Ruthenium 106 Plaques Without Verification of Plaque Position Is Associated With Local Tumor Recurrence and Death in Posterior Uveal Melanoma

PURPOSE

Brachytherapy with episcleral plaques is the most common primary tumor treatment for uveal melanoma. This study aimed to compare the risk of tumor recurrence and metastatic death between 2 frequently used ruthenium 106 plaque designs: CCB (20.2 mm) and CCA (15.3 mm).

METHODS AND MATERIALS

Data were obtained from 1387 consecutive patients treated at St. Erik Eye Hospital, Stockholm, Sweden between 1981 and 2022 (439 with CCA and 948 with CCB plaques). During the period, scleral transillumination was performed to delineate tumor margins before plaque insertion, but accurate plaque positioning was not verified after scleral attachment, and no minimum scleral dose was used.

RESULTS

Patients treated with CCA plaques had smaller tumors than those treated with CCB plaques (mean diameter, 8.6 vs 10.5 mm; P < .001). There were no differences in patient sex, age, tumor distance to the optic disc, tumor apex dose, dose rate, or in rates of ciliary body involvement, eccentric plaque placement, or adjunct transpupillary thermotherapy (TTT). The average difference between plaque and tumor diameter was greater with the CCB plaque, and a smaller difference was an independent predictor of tumor recurrence. The 15-year incidence of tumor recurrence was 28% and 15% after treatment with CCA and CCB plaques, respectively (competing risk analysis, P < .001). Multivariate Cox regression analysis revealed a lower risk for tumor recurrence with CCB plaques (hazard ratio, 0.50). Similarly, patients treated with CCB plaques had a lower risk for uveal melanoma-related mortality (hazard ratio, 0.77). The risk for either outcome was not lower for patients treated with adjunct TTT. Uni- and multivariate time-dependent Cox regressions demonstrated that tumor recurrence was associated with uveal melanoma-related and all-cause mortality.

CONCLUSIONS

Compared with 20-mm plaques, brachytherapy with 15-mm ruthenium plaques is associated with a higher risk for tumor recurrence and death. These adverse outcomes may be avoided by increasing safety margins and implementing effective methods to verify accurate plaque positioning.

Deterioration of Visual Acuity after Brachytherapy and Proton Therapy of Uveal Melanoma, and Methods of Counteracting This Complication Based on Recent Publications

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. The eyeball is the most common extracutaneous location of melanoma. UM is a huge threat to a patient's life. It metastasizes distantly via blood vessels, but it can also spread locally and infiltrate extraocular structures. The treatment uses surgical methods, which include, among others, enucleation and conservative methods, such as brachytherapy (BT), proton therapy (PT), stereotactic radiotherapy (SRT), stereotactic radiosurgery (SRS), transpupillary thermotherapy (TTT) and photodynamic therapy. The key advantage of radiotherapy, which is currently used in most patients, is the preservation of the eyeball with the risk of metastasis and mortality comparable to that of enucleation. Unfortunately, radiotherapy very often leads to a significant deterioration in visual acuity (VA) as a result of radiation complications. This article is a review of the latest research on ruthenium-106 (Ru-106) brachytherapy, iodine-125 (I-125) brachytherapy and proton therapy of uveal melanoma that took into account the deterioration of eye function after therapy, and also the latest studies presenting the new concepts of modifications to the applied treatments in order to reduce radiation complications and maintain better visual acuity in treated patients.