High-dose spatially-fractionated radiation (GRID): A new paradigm in the management of advanced cancers

Purpose: With the advent of megavoltage radiation, the concept of spatially -fractionated (SFR) radiation has been abandoned for the last several decad es; yet, historically, it has been proven to be safe and effective in deliv ering large cumulative doses (> 100 Gy) of radiation in the treatment of ca ncer. SFR radiation has been adapted to megavoltage beams using a specially constructed grid. This study evaluates the toxicity and effectiveness of t his approach in treatment of advanced and bulky cancers. Methods and Materials: From January 1995 through March 1998, 71 patients wi th advanced bulky tumors (tumor sizes > 8 cm) were treated with SFR high-do se external beam megavoltage radiation using a GRID technique. Sixteen pati ents received GRID treatments to multiple sites and a total of 87 sites wer e irradiated. A 50:50 GRID (open to closed area) was utilized, and a single dose of 1,000-2,000 cGy (median 1,500 cGy) to D-max was delivered utilizin g 6 MV photons. Sixty-three patients received high-dose GRID therapy for pa lliation (pain, mass, bleeding, or dyspnea). In 8 patients, GRID therapy wa s given as part of a definitive treatment combined with conventionally-frac tionated external beam irradiation (dose range 5,000-7,000 cGy) followed by subsequent surgery. Forty-seven patients were treated with GRID radiation followed by additional fractionated external beam irradiation, and 14 patie nts were treated with GRID alone. Thirty-one treatments were delivered to t he abdomen and pelvis, 30 to the head and neck region, 15 to the thorax, an d 11 to the extremities. Results: For palliative treatments, a 78% response rate was observed for pa in, including a complete response (CR) of 19.5%, and a partial response (PR ) of 58.5% in these large bulky tumors. A 72.5% response rate was observed for mass effect (CR 14.6%, PR 52.9%). The response rate observed for bleedi ng was 100% (50% CR, 50% PR) and for dyspnea, a 60% PR rate only. A relativ ely higher response rate (CR 23.3%, PR 60%) was observed in patients who re ceived GRID treatment in the head and neck area. No grade 3 late skin, subc utaneous, mucosal, GI, or CNS complications were observed in any patient in spite of these high doses. In the 8 patients who received GRID treatment f or definitive treatment, a clinical CR was observed in 5 patients (62.5%) a nd a pathological complete response was confirmed in the operative specimen in 4 patients (50%). Conclusion: The efficacy and safety of using a large fraction of SFR radiat ion was confirmed by this study and substantiates our earlier results. In s elected patients with bulky tumors (> 8 cm), SFR radiation can be combined with fractionated external beam irradiation to yield improved local control of disease, both for palliation and selective definitive treatment, especi ally where conventional treatment alone has a limited chance of success. (C ) 1999 Elsevier Science Inc.