Practice Patterns of Spatially Fractionated Radiation Therapy: A Clinical Practice Survey

PurposeSpatially fractionated radiation therapy (SFRT) is increasingly used for bulky advanced tumors, but specifics of clinical SFRT practice remain elusive. This study aimed to determine practice patterns of GRID and Lattice therapy (LRT) based SFRT.Materials and MethodsA survey was designed to identify radiation oncologists' practice patterns of patient selection for SFRT, dosing/planning, dosimetric parameter use, SFRT platforms/techniques, combinations of SFRT with conventional external beam radiation therapy (cERT) and multimodality therapies, and physicists' technical implementation, delivery and quality procedures. Data were summarized using descriptive statistics. Group comparisons were analyzed with permutation tests.ResultsThe majority of practicing radiation oncologists (100% - US, 72.7% - global) considered SFRT an accepted standard-of-care radiotherapy option for bulky/advanced tumors. Treatment of metastases/recurrences and non-metastatic primary tumors, predominantly head and neck, lung cancer and sarcoma, was commonly practiced.In palliative SFRT, regimens of 15-18 Gy/1 fraction predominated (51.3%); and in curative-intent treatment of non-metastatic tumors 15 Gy/1 fraction (28.0%) and fractionated SFRT (24.0%) were most common. SFRT was combined with cERT commonly but not always in palliative (78.6%) and curative-intent (85.7%) treatment. SFRT–cERT time sequencing and cERT dose adjustments were variable. In curative-intent treatment, concurrent chemotherapy and immunotherapy were found acceptable by 54.5% and 28.6%, respectively. Use of SFRT dosimetric parameters was highly variable and differed between GRID and LRT. SFRT heterogeneity dosimetric parameters were more commonly used (p=0.008) and more commonly thought to influence local control (Peak dose, p=0.008) in LRT than in GRID therapy.ConclusionsSFRT has already evolved as a clinical practice pattern for advanced/bulky tumors. Major treatment approaches are consistent and follow the literature, but SFRT–cERT combination/sequencing and clinical utilization of dosimetric parameters are variable. These areas may benefit from targeted education and standardization, and knowledge gaps may be filled by incorporating identified inconsistencies into future clinical research.