title: Intensity-modulated radiotherapy in patients with cervical cancer. An intra-individual comparison of prone and supine positioning.
abstract: BACKGROUND
  Chemoradiation for cervical cancer patients is associated with considerable gastrointestinal toxicity. Intensity-modulated radiotherapy (IMRT) has demonstrated superiority in terms of target coverage and normal tissue sparing in comparison to conventional 3D planning in gynaecological malignancies. Whether IMRT in prone (PP) or supine position (SP) might be beneficial for cervical cancer patients remains partially unanswered.
  
  
  METHODS
  10 patients on FIGO stage IB-III cervical cancer, 6 patients for definitive and 4 patients for adjuvant external beam pelvic RT, were planned in PP and SP using a 7-field IMRT technique. IMRT plans for PP and SP (mean dose, Dmean 50.4 Gy) were optimized in terms of PTV coverage (1st priority) and small bowel sparing (2nd priority). A comparison of DVH parameters for PTV, small bowel, bladder, and rectum was performed.
  
  
  RESULTS
  The comparison showed a similar PTV coverage of 95% of the prescribed dose and for target conformity in IMRT plans (PP, SP). PTV, rectum and bladder volumes were comparable for PP and SP. Significantly larger volumes of small bowel were found in PP (436 cc, + 35%, p = 0.01). PP decreased the volume of small bowel at 20-50.4 Gy (p < 0.05) and increased the rectum volumes covered by doses from 10-40 Gy (p < 0.01), the V50.4 was < 5% in both treatment positions. Bladder sparing was significant better at 50.4 Gy (p = 0.03) for PP.
  
  
  CONCLUSIONS
  In this dosimetric study, we demonstrated that pelvic IMRT in prone position for patients with cervical cancer seems to be beneficial in reducing small bowel volume at doses >or=20 Gy while providing similar target coverage and target conformity. The use of frequent image guidance with KV (kilovolt) or MV (megavolt) computer tomography can reduce set-up deviations, and treatment in prone position can be done with a higher set-up accuracy. Clinical outcome studies are needed to affirm lower toxicity.
authors.affiliation: Department of Radiooncology, Charité University Hospital, Campus CCM and CVK, Augustenburger Platz 1, Berlin, Germany. carmen.stromberger@charite.de
authors.forename: Carmen
authors.initials: C
authors.lastname: Stromberger
authors.forename: Yves
authors.initials: Y
authors.lastname: Kom
authors.forename: Michael
authors.initials: M
authors.lastname: Kawgan-Kagan
authors.forename: Tristan
authors.initials: T
authors.lastname: Mensing
authors.forename: Ulrich
authors.initials: U
authors.lastname: Jahn
authors.forename: Achim
authors.initials: A
authors.lastname: Schneider
authors.forename: Volker
authors.initials: V
authors.lastname: Budach
authors.forename: Christhardt
authors.initials: C
authors.lastname: Köhler
authors.forename: Simone
authors.initials: S
authors.lastname: Marnitz
mesh_terms: D005260:Female; D006801:Humans; D009367:Neoplasm Staging; D016684:Prone Position; D011874:Radiometry; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D016683:Supine Position; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*