[Ga68] DOTATATE PET/MRI-guided radiosurgical treatment planning and response assessment in meningiomas.

BACKGROUND: Our purpose was to determine the utility of [68Ga]-DOTATATE PET/MRI in meningioma response assessment following radiosurgery. METHODS: Patients with meningioma prospectively underwent postoperative DOTATATE PET/MRI. Co-registered PET and gadolinium-enhanced T1-weighted MRI were employed for radiosurgery planning. Follow-up DOTATATE PET/MRI was performed at 6-12 months post-radiosurgery. Maximum absolute standardized uptake value (SUV) and SUV ratio (SUVRSSS) referencing superior sagittal sinus (SSS) blood pool were obtained. Size change was determined by Response Assessment in Neuro-Oncology (RANO) criteria. Association of SUVRSSS change magnitude and progression-free survival (PFS) was evaluated using Cox regression. RESULTS: Twenty-seven patients with 64 tumors (26% World Health Organization [WHO]-1, 41% WHO-2, 26% WHO-3, and 7% WHO-unknown) were prospectively followed post stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT; mean dose: 30 Gy, modal dose 35 Gy, mean of 5 fractions). Post-irradiation SUV and SUVRSSS decreased by 37.4% and 44.4%, respectively (P < .0001). Size product decreased by 8.9%, thus failing to reach the 25% significance threshold as determined by RANO guidelines. Mean follow-up time was 26 months (range: 6-44). Overall mean PFS was 83% and 100%/100%/54% in WHO-1/-2/-3 subcohorts, respectively, at 34 months. At maximum follow-up (42-44 months), PFS was 100%/83%/54% in WHO-1/-2/-3 subcohorts, respectively. Cox regression analyses revealed a hazard ratio of 0.48 for 10-unit reduction in SUVRSSS in the SRS cohort. CONCLUSIONS: DOTATATE PET SUV and SUVRSSS demonstrated marked, significant decrease post-radiosurgery. Lesion size decrease was statistically significant; however, it was not clinically significant by RANO criteria. DOTATATE PET/MR thus represents a promising imaging biomarker for response assessment in meningiomas treated with radiosurgery. CLINICALTRIALS.GOV IDENTIFIER: NCT04081701.

Radiation treatment to a postresection primary mucoepidermoid carcinoma (MEC) of the conjunctiva with positive margins at the Tenon's fascia-A case study.

The primary occurrence of mucoepidermoid carcinoma (MEC) of the conjunctiva is extremely rare, aggressive, and easily mistaken for squamous cell carcinoma. With fewer than 50 cases reported in the literature, there is no consensus on the most effective treatment. Radiation is an alternative to enucleation or orbital exenteration with the potential of eye preservation. We investigated several radiation approaches for a case with postresection positive margins at Tenon's fascia, and reported the patient's clinical course during the treatment and for a short time thereafter. An otherwise healthy 64-year-old male presented with MEC extending to the deep margin at the Tenon's fascia. Plans for 4 different radiation therapy treatment modalities (Intensity Modulated Radiation Therapy [IMRT], Volumetric Modulated Radiation Therapy [VMAT], double scattering (DS) proton, and reverse eye plaque low dose rate [LDR] ) were created and compared based on tumor coverage and normal tissue doses. The planning target volume (PTV) was too large and nonuniform for an eye plaque application. Using the largest plaque available (22 mm), the calculated minimum dose to the PTV was 57% while the dose to the skin was 1000% of the prescription. The proton plan completely spared the contralateral ocular structures and reduced the max doses to the ipsilateral macula and optic nerve, but was not clinically available at the time of treatment. The IMRT and VMAT plans produced similar dose distributions to each other, but VMAT further minimized dose to the ipsilateral eye. Due to the uniqueness of this case, a thorough study of the available radiation treatment options was deemed necessary. All of the external beam treatment techniques produced acceptable plans with VMAT producing the best available plan in this case. The patient was treated with the VMAT plan with a prescription of 6600 cGy in 30 fractions. At 5 months post-treatment, the patient is recovering from expected acute responses to radiation with follow ups scheduled.

A complete workflow for utilizing Monte Carlo toolkits in clinical cases for a double-scattering proton therapy system.

The methods described in this paper allow end users to utilize Monte Carlo (MC) toolkits for patient-specific dose simulation and perform analysis and plan comparisons for double-scattering proton therapy systems. The authors aim to fill two aspects of this process previously not explicitly published. The first one addresses the modeling of field-specific components in simulation space. Patient-specific compensator and aperture models are exported from treatment planning system and converted to STL format using a combination of software tools including Matlab and Autodesk's Netfabb. They are then loaded into the MC geometry for simulation purpose. The second details a method for easily visualizing and comparing simulated doses with the dose calculated from the treatment planning system. This system is established by utilizing the open source software 3D Slicer. The methodology was demonstrated with a two-field proton treatment plan on the IROC lung phantom. Profiles and two-dimensional (2D) dose planes through the target isocenter were analyzed using our in-house software tools. This present workflow and set of codes can be easily adapted by other groups for their clinical practice.