title: Critical appraisal of volumetric modulated arc therapy in stereotactic body radiation therapy for metastases to abdominal lymph nodes.
abstract: OBJECTIVE
  A planning study was performed comparing volumetric modulated arcs, RapidArc (RA), fixed beam IMRT (IM), and conformal radiotherapy (CRT) with multiple static fields or short conformal arcs in a series of patients treated with hypofractionated stereotactic body radiation therapy (SBRT) for solitary or oligo-metastases from different tumors to abdominal lymph nodes.
  
  
  METHODS
  Fourteen patients were included in the study. Dose prescription was set to 45 Gy (mean dose to clinical target volume [CTV]) in six fractions of 7.5 Gy. Objectives for CTV and planning target volume (PTV) were as follows: Dose(min) >95%, Dose(max) <107%. For organs at risk the following objectives were used: Maximum dose to spine <18 Gy; V(15Gy) <35% for both kidneys, V(36Gy) <1% for duodenum, V(36Gy) <3% for stomach and small bowel, V(15Gy) <(total liver volume--700 cm(3)) for liver. Dose-volume histograms were evaluated to assess plan quality.
  
  
  RESULTS
  Planning objectives on CTV and PTV were achieved by all techniques. Use of RA improved PTV coverage (V(95%) = 90.2% +/- 5.2% for RA compared with 82.5% +/- 9.6% and 84.5% +/- 8.2% for CRT and IM, respectively). Most planning objectives for organs at risk were met by all techniques except for the duodenum, small bowel, and stomach, in which the CRT plans exceeded the dose/volume constraints in some patients. The MU/fraction values were as follows: 2186 +/- 211 for RA, 2583 +/- 699 for IM, and 1554 +/- 153 for CRT. Effective treatment time resulted as follows: 3.7 +/- 0.4 min for RA, 10.6 +/- 1.2 min for IM, and 6.3 +/- 0.5 min for CRT.
  
  
  CONCLUSIONS
  Delivery of SBRT by RA showed improvements in conformal avoidance with respect to standard conformal irradiation. Delivery parameters confirmed logistical advantages of RA, particularly compared with IM.
authors.affiliation: Istituto Clinico Humanitas, Radiation Oncology, Rozzano, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Bignardi
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
authors.forename: Paola
authors.initials: P
authors.lastname: Lattuada
authors.forename: Pietro
authors.initials: P
authors.lastname: Mancosu
authors.forename: Piera
authors.initials: P
authors.lastname: Navarria
authors.forename: Gaetano
authors.initials: G
authors.lastname: Urso
authors.forename: Sabrina
authors.initials: S
authors.lastname: Vigorito
authors.forename: Marta
authors.initials: M
authors.lastname: Scorsetti
mesh_terms: D000005:Abdomen; D000328:Adult; D000368:Aged; D019583:Dose Fractionation, Radiation; D004386:Duodenum / Q000528:radiation effects; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects; D007668:Kidney / Q000528:radiation effects; D008099:Liver / Q000528:radiation effects; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D013116:Spinal Cord / Q000528:radiation effects; D013679:Technology, Radiologic / Q000379:methods; D047368:Tumor Burden