title: High-dose spatially fractionated GRID radiation therapy (SFGRT): a comparison of treatment outcomes with Cerrobend vs. MLC SFGRT.
abstract: OBJECTIVE
  Spatially fractionated GRID radiotherapy (SFGRT) using a customized Cerrobend block has been used to improve response rates in patients with bulky tumors. The clinical efficacy of our own multileaf collimator (MLC) technique is unknown. We undertook a retrospective analysis to compare clinical response rates attained using these two techniques.
  
  
  METHODS
  Seventy-nine patients with bulky tumors (median diameter, 7.6 cm; range, 4-30 cm) treated with SFGRT were reviewed. Between 2003 and late 2005, the Cerrobend block technique (n = 39) was used. Between late 2005 and 2008, SFGRT was delivered using MLC-shaped fields (n = 40). Dose was prescribed to dmax (depth of maximum dose) and was typically 15 Gy. Eighty percent of patients in both groups received external beam radiotherapy in addition to SFGRT. The two-sided Fisher-Freeman-Halton test was used to compare pain and mass effect response rates between the two groups.
  
  
  RESULTS
  Sixty-one patients (77%) were treated for palliative intent and 18 (23%) for curative intent. The majority of patients had either lung or head-and-neck primaries in both groups; the most frequent site of SFGRT application was the neck. The majority of patients complained of either pain (65%) or mass effect (58%) at intake. Overall response rates for pain and mass response were no different between the Cerrobend and MLC groups: pain, 75% and 74%, respectively (p = 0.50), and mass effect, 67% and 73%, respectively (p = 0.85). The majority of toxicities were Grade 1 or 2, and only 3 patients had late Grade 3-4 toxicities.
  
  
  CONCLUSIONS
  MLC-based and Cerrobend-based SFGRT have comparable and encouraging response rates when used either in the palliative or curative setting. MLC-based SGFRT should allow clinics to more easily adopt this novel treatment approach for the treatment of bulky tumors.
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA. gneuner@umm.edu
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Neuner
authors.forename: Majid M
authors.initials: MM
authors.lastname: Mohiuddin
authors.forename: Noam
authors.initials: N
authors.lastname: Vander Walde
authors.forename: Olga
authors.initials: O
authors.lastname: Goloubeva
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ha
authors.forename: Cedric X
authors.initials: CX
authors.lastname: Yu
authors.forename: William F
authors.initials: WF
authors.lastname: Regine
mesh_terms: D019583:Dose Fractionation, Radiation; D004867:Equipment Design; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy; D008297:Male; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D010146:Pain / Q000209:etiology / Q000532:radiotherapy; D010166:Palliative Care / Q000379:methods; D010315:Particle Accelerators; D055618:Radiation Equipment and Supplies; D011832:Radiation Injuries / Q000150:complications / Q000473:pathology; D012189:Retrospective Studies; D016896:Treatment Outcome; D047368:Tumor Burden