Dosimetric Validation for Prospective Clinical Trial of GRID Collimator-Based Spatially Fractionated Radiation Therapy: Dose Metrics Consistency and Heterogeneous Pattern Reproducibility.

PURPOSE: Dose heterogeneity within a tumor target is likely responsible for the biologic effects and local tumor control from spatially fractionated radiation therapy (SFRT). This study used a commercially available GRID-pattern dose mudulated nonuniform radiation therapy (GRID) collimator to assess the interplan variability of heterogeneity dose metrics in patients with various bulky tumor sizes and depths. METHODS AND MATERIALS: The 3-dimensional heterogeneity metrics of 14 bulky tumors, ranging from 155 to 2161 cm3 in volume, 6 to 23 cm in equivalent diameter, and 3 to 13 cm in depth, and treated with GRID collimator-based SFRT were studied. A prescription dose of 15 Gy was given at the tumor center with 6 MV photons. The dose-volume histogram indices, dose heterogeneity parameters, and peak/valley dose ratios were derived; the equivalent uniform doses of cancer cells with various radiosensitivities in each plan were estimated. To account for the spatial fractionation, high dose core number density of the tumor target was defined and calculated. RESULTS: Among 14 plans, the dose-volume histogram indices D5, D10, D50, D90, and D95 (doses covering 5%, 10%, 50%, 90%, and 95% of the target volume) were found within 10% variation. The dose ratio of D10/D90 also showed a moderate consistency (range, 3.9-5.0; mean, 4.4). The equivalent uniform doses were consistent, ranging from 4.3 to 5.5 Gy, mean 4.6 Gy, for radiosensitive cancer cells and from 5.8 to 6.9 Gy, mean 6.2 Gy, for radioresistant cancer cells. The high dose core number density was within 20% among all plans. CONCLUSIONS: GRID collimator-based SFRT delivers a consistent heterogeneity dose distribution and high dose core density across bulky tumor plans. The interplan reproducibility and simplicity of GRID therapy may be useful for certain clinical indications and interinstitutional clinical trial design, and its heterogeneity metrics may help guide multileaf-collimator-based SFRT planning to achieve similar or further optimized dose distributions.

An interdisciplinary consensus on the management of brain metastases in patients with renal cell carcinoma.

Brain metastases are a challenging manifestation of renal cell carcinoma. We have a limited understanding of brain metastasis tumor and immune biology, drivers of resistance to systemic treatment, and their overall poor prognosis. Current data support a multimodal treatment strategy with radiation treatment and/or surgery. Nonetheless, the optimal approach for the management of brain metastases from renal cell carcinoma remains unclear. To improve patient care, the authors sought to standardize practical management strategies. They performed an unstructured literature review and elaborated on the current management strategies through an international group of experts from different disciplines assembled via the network of the International Kidney Cancer Coalition. Experts from different disciplines were administered a survey to answer questions related to current challenges and unmet patient needs. On the basis of the integrated approach of literature review and survey study results, the authors built algorithms for the management of single and multiple brain metastases in patients with renal cell carcinoma. The literature review, consensus statements, and algorithms presented in this report can serve as a framework guiding treatment decisions for patients. CA Cancer J Clin. 2022;72:454-489.