title: Robotic radiosurgery as an alternative to brachytherapy for cervical cancer patients.
abstract: OBJECTIVE
  To compare MRI-guided brachytherapy (BT) and two different dose prescriptions for robotic radiosurgery (RRS) in locally advanced cervical cancer.
  
  
  METHODS
  Eleven patients with FIGO stage IIB-IIIB cervical cancer underwent RRS instead of BT for various reasons. A total dose of 30 Gy was administered in five fractions. The maximum dose was chosen such that the prescribed dose was 70 % of the maximum dose (RRS70). To simulate BT more closely, additional plan calculations were carried out for a higher maximum dose with the same enclosing dose of 30 Gy being now 25 % of the maximum dose (RRS25). BT plans were calculated for the same patients (BTRRS). Finally, the resulting three sets of treatment plans were compared with 38 other patients treated with MRI-guided BT and the same dose prescription (BTref). Plan comparisons were performed based on DVH parameters with regard to target coverage (V100), conformation number (CN), and sparing of the organs at risk (OARs).
  
  
  RESULTS
  The best coverage of V100 = 100 ± 0 % was obtained with RRS25, followed by RRS70 with 97.1 ± 2.7 %, BTref with 90.9 ± 8.9 %, and the intraindividual BTRRS with 80.6 ± 6.4 %. The sparing of OARs was associated with D0.1 cc, D2 cc, and D5 cc to the rectum, sigmoid, and bladder walls. OAR doses were compliant with the GEC-ESTRO guidelines and comparable among RRS70, RRS25, BTRRS, and BTref. By contrast, RRS25 could not fulfill these guidelines, exceeding considerably the tolerable dose constraints for the walls of the critical OARs.
  
  
  CONCLUSIONS
  Despite of the excellent coverage and higher maximum dose, the unacceptably high exposure to the OARs disqualified RRS25 as an alternative for BT in cervical cancer patients. By contrast, RRS70 offered the best protection for the OARs, comparable to BT, and even better target coverage and conformity than BT.
authors.affiliation: Department of Radiation Oncology, Charité University Hospital, Charitéplatz 1, 10117, Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Neumann
authors.forename: Anne
authors.initials: A
authors.lastname: Kluge
authors.forename: Olga
authors.initials: O
authors.lastname: Lyubina
authors.forename: Waldemar
authors.initials: W
authors.lastname: Wlodarczyk
authors.forename: Ulrich
authors.initials: U
authors.lastname: Jahn
authors.forename: Christhardt
authors.initials: C
authors.lastname: Köhler
authors.forename: Volker
authors.initials: V
authors.lastname: Budach
authors.forename: Markus
authors.initials: M
authors.lastname: Kufeld
authors.forename: Simone
authors.initials: S
authors.lastname: Marnitz
mesh_terms: D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D008875:Middle Aged; D009367:Neoplasm Staging; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012371:Robotics / Q000379:methods*; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000601:surgery*