Outcomes of Spatially Fractionated GRID Radiation Therapy in the Treatment of Bulky Tumors

Purpose/Objectives: In this study, the authors performed a single-institution retrospective analysis of outcomes of patients with bulky malignant tumors treated with spatially fractionated GRID radiotherapy (SFGRT). Tumor response, symptom control, therapy tolerance, and acute toxicities were evaluated.Materials/Methods: Patients treated with SFGRT between1976 and 2013 were identified. The medical records of these 13 patients treated from 2007 to 2013 were reviewed. All patients presented with bulky tumors in the head and neck region, the majority of which were of squamous cell carcinoma histology, others including anaplastic carcinoma, poorly differentiated invasive carcinoma, and MPNST. Patient ages ranged from 13 to 83 years. All were planned to receive conventionally-fractionated EBRT to follow SFGRT, with a wide variety of dose prescription and fractionation schedules. SFGRT was delivered over one fraction of either 15 Gy or 20 Gy, using multileaf collimation.Results: Of 13 patients, 12 were being treated for palliation of local tumor symptoms to include bleeding, restricted motion from tumor bulk, and pain. 8/12 patients (67%) experienced symptom improvement during the course of therapy. Average maximum tumor diameter was 10 cm. Substantial decrease in tumor size was observed in 6/10 tumors (60%) being treated primarily for this purpose, with greater than 50% size reduction in patients with this follow-up data available. Of the 4 patients without tumor shrinkage, 2 patients received a curtailed course of EBRT or relatively low dose of EBRT, while a third had a long treatment break secondary to bleeding. 1 patient being treated definitively received chemotherapy concurrently and had substantial reduction in mass size. All tumor histologies responded to treatment with the exception of anaplastic carcinoma. RTOG grade III skin or mucous membrane toxicity was seen in 4 patients, while grade IV toxicity developed in 4 patients, with bleeding or ulceration. One patient required tumor embolization secondary to uncontrolled bleeding.Conclusions: Our single-institution review suggests that SFGRT is an effective radiation therapy modality for large, symptomatic tumors that can provide timely improvement in patient quality of life. At initial analysis, the toxicity associated with SFGRT does appear to be substantial. However, given the that these tumors generally compromise skin and blood vessels in the proximity at presentation, these adverse effects can be considered the result of normal tumor biology, rather than treatment toxicity. The use of this modality of therapy is relatively limited, likely in part due to the small body of data available regarding its efficacy and safety of delivery. With this study, we provide added perspective to practitioners, possibly leading to increased application of SFGRT in the clinical setting for patients with these unique presentations.

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Outcomes of Spatially Fractionated GRID Radiation Therapy in the Treatment of Bulky Tumors