Diagnosis and detection of primary uveal melanoma are primarily based on clinical examination by ultrasound and indirect ophthalmoscopy. However, MRI scans should also be performed to confirm the diagnosis and mark the patient for radiation therapy. Linear accelerator-based stereotactic irradiation is the right treatment for posterior uveal melanoma, is well-tolerated, and can be offered to medium-sized uveal melanoma patients . Radiotherapy for uveal melanoma by CyberKnife system or stereotactic radiosurgery must quantify the reproducibility of the eye immobilization system. In all these modalities, it is necessary to use scans, x, y, and z to see the displacements of the lens, optic nerve insertion, and other structures to compare scans during the irradiation, and later on also to find the results of radiosurgery by regular check-ups .
Until now, there no multicenter trial to assess the efficacy and tumor volumetry of stereotactic radiosurgery has been performed. Also, the same is valid for gamma knife radiosurgery for intraocular melanoma. Results from more studies prove, for example, that irradiation techniques (by including the linear accelerator, proton beam irradiation, or gamma knife) have similar local results if compared to brachytherapy (typically, tumor control rate). The studies conclude that Gamma knife radiosurgery or linear accelerator stereotactic irradiation for uveal melanoma is the suitable alternatives in treating intraocular melanoma patients they were not indicated for brachytherapy [22, 23]. The majority of treated patients in our study were in stage T1, thus suitable for plaque brachytherapy, but this method is not available in Slovakia in the last decades.
In the case of the report by Jacobsen et al. 94-year-old man with a prior ocular history of age-related macular degeneration in both eyes was referred to an ophthalmology clinic for the routine-dilated fundus test. Contrast orbital MRI showed the sub-centimetric region of abnormal contrast enhancement extending into the immediately adjacent orbital fat, suspected of scleral invasion and small extrascleral extension of the lesion. Ultrasound was important to define the difference between intraocular bleeding and secondary retinal detachment. Both methods were important to provide the correct diagnosis before treatment. It is important to define the intraocular lesion, as metastatic uveal melanoma of the skin tissue can also occur, although it is exceedingly rare . The optimal treatment for metastatic melanoma of the skin into the eyeball is not known but can include radiation therapy or systemic immunotherapy . Survival after metastasis does not depend on the initial characteristics of the intraocular tumor. Even small tumors have a higher risk of metastasis after 10 years . The potential spread after local destruction with endovitreal resection (removal) of the large uveal melanoma is also important for defining the volume of intraocular melanoma .
The use of contrast-enhanced ultrasound in the quantitative assessment of the response of intraocular melanoma to gamma-knife radiosurgery investigates whether changes in tumor vascularization precede the thickness reduction, which on average occurs at 12 radiosurgery after 12 months or later, as mentioned in the study of Venturini. The reduction of melanoma thickness occurred in 6 of the 10 patients, whereas the reduction in all quantitative parameters in all 10 patients . Accurate tumor volume measured values can facilitate more reliable estimates of tumor regression or regrowth after treatment of globe-retaining choroidal melanomas and can be one of the valuable prognostic indicators after treatment . But by stereotactic irradiation to observe a reduction of tumor volume, it is necessary to send regularly the patient to MRI after therapy. In our Center in the first 5 years interval after stereotactic irradiation, we send patients every 6 months for MRI and later at least once per year. Of course, ultrasound is also regularly performed by an ophthalmologist. In any case, ophthalmic ultrasonography performed by an ophthalmologist is still the most important tool to assess and monitor the progression of uveal melanomas and should be performed at certain intervals in each patient after stereotactic irradiation, until the end of his/her life. But last year and today we still do have problems keeping this interval due to COVID problems.
CT or MRI are considered to be the standard for the planning procedure also in stereotactic irradiation. The ultrasound measurement can be examiner dependent and less accurate with peripheral locations of the tumor. MRI was used to detect the extrascleral extension and in our study were these patients excluded from a one-day session of irradiation therapy. In our study, the patients with extrascleral extension were not indicated for stereotactic irradiation.
There is no consensus in the literature on how exactly the volume of the uveal melanoma should exactly be calculated due to the various forms of the uveal melanoma (dome versus mushroom shape). The rotating ellipsoid formula described by Richtig et al. was not reproducible on the larger data set. In our study authors, we provide the mean (median) horizontal diameter of the tumor and mean vertical diameter of the tumor (thickness, elevation of the lesion) but not the transverse diameter of the tumor, which in some cases can be bigger than the longitudinal section [19, 30].
In many countries, ophthalmologists do not use MRI to diagnose or observe post-irradiation changes in uveal tumor volume, they use only ultrasound. However, the ultrasound technique is routinely available in ophthalmology centers and is not so expensive, compared to MRI.
CT and MRI images are the base for stereotactic therapy in uveal melanoma. Why? It is due to safety and excellent local control. In our study, all patients underwent ocular B-scan ultrasound as the first step to assess the stage of the melanoma, and then every patient was sent to MRI to detect possible extrascleral extension. Our experience still confirms that ocular ultrasound is essential in patients with uveal melanoma. In patients in whom stereotactic irradiation was indicated based on the ultrasound findings, the MRI remains the next fundamental step for verification. In this treatment, we excluded the patients with tumor volume below 0.1 cm3 because the extremely small tumor volumes are not suitable for irradiation and cause problems with stereotactic planning.
The measured values of tumor volume, measured by ultrasound and MRI, were different, and the stereotactic irradiation was performed according to the MRI or CT image, but not ultrasound. Ultrasound is a common method for the ophthalmic oncologist, so MRI is necessary for planning, but follow-up and response should be judged by ultrasound, not frequent MRI in practice but in certain conditions, it is necessary to use MRI to evaluate the volume regression, because the interpretation of ultrasound image is difficult.
The findings from the MRI verification step, which can detect possible extraocular extension, were also examined by our neuro-radiologist to evaluate specific inflammation, vascular formation (e.g., feeding vessel), or movement artifacts. These findings cannot be generalized to every patient, and evaluation and radiation therapy should be planned on a case-by-case basis. Thus, an ultrasound must be performed by an experienced ophthalmologist in all patients with uveal melanoma. Additionally, each patient is unique, the measuring procedure and resources are often limited, and the ocular ultrasound should represent not only a unique imaging modality of choice in the search for extrascleral spreading in uveal melanoma but also a basic examination in onco-ophthalmology.