title: 45 or 50 Gy, Which is the Optimal Radiotherapy Pelvic Dose in Locally Advanced Cervical Cancer in the Perspective of Reaching Magnetic Resonance Image-guided Adaptive Brachytherapy Planning Aims?
abstract: OBJECTIVE
  In locally advanced cervical cancer, the dose delivered results from the sum of external beam radiotherapy and brachytherapy, and is limited by the surrounding organs at risk. The balance between both techniques influences the total dose delivered to the high-risk clinical target volume (HR-CTV). The aim of the present study was to compare the ability of reaching different planning aims after external beam radiotherapy pelvic doses of 45 Gy in 25 fractions or 50.4 Gy in 28 fractions, both considered as standard prescriptions.
  
  
  METHODS
  The optimised plans of 120 patients treated with pelvic chemoradiation followed by magnetic resonance image-guided intracavitary brachytherapy were reviewed. The doses per pulse were calculated, and the number of pulses required to reach the planning aims, or a limiting dose constraint to organs at risk, was calculated. All doses were converted to 2-Gy equivalents. Three scenarios were applied consisting of different sets of planning aims: 85 and 60 Gy for the HR-CTV and the intermediate-risk CTV (IR-CTV) D90 (minimal dose received by 90% of the volume) in scenario 1, 90 and 60 Gy, respectively, for scenarios 2 and 3. For organs at risk, dose constraints were 90, 75 and 75 Gy to the bladder, rectum and sigmoid D2cm(3), respectively, in scenarios 1 and 2, and 80, 65 and 70 Gy in scenario 3.
  
  
  RESULTS
  A similar HR-CTV D90 could have been reached in scenarios 1 and 2 according to both pelvic doses. In scenario 3, a higher mean HR-CTV could have been reached in the 45 Gy arm (83.5 ± 8.0 versus 82.4 ± 8.0, P < 0.0001). The mean D2cm(3) of organs at risk was systematically and significantly increased after a delivery of 50.4 Gy to the pelvis, from 0.9 to 2.89 Gy. The proportions of plans reaching planning aims were 85.8, 72.5 and 42.5% after 45 Gy and 85.5, 67.5 and 33.3% after 50.4 Gy according to scenarios 1, 2 and 3, respectively. According to scenario 3, 50.4 Gy, the reachable HR-CTV D90 was higher in 30% of the cases, by 2 Gy in two cases. Those cases were unpredictable and due to unfavourable organs at risk topography and poor response to external beam radiotherapy.
  
  
  CONCLUSIONS
  The delivery of 45 Gy in 25 fractions to the pelvis before brachytherapy warrants a higher probability to reach brachytherapy planning aims, in comparison with 50.4 Gy in 28 fractions.
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France; Molecular Radiotherapy - UMR1030, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France. Electronic address: renaud.mazeron@gustaveroussy.fr.
authors.forename: R
authors.initials: R
authors.lastname: Mazeron
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: C
authors.initials: C
authors.lastname: Petit
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: E
authors.initials: E
authors.lastname: Rivin
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: E
authors.initials: E
authors.lastname: Limkin
authors.affiliation: Medical Physics, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: I
authors.initials: I
authors.lastname: Dumas
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: P
authors.initials: P
authors.lastname: Maroun
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: P
authors.initials: P
authors.lastname: Annede
authors.affiliation: Medical Physics, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: F
authors.initials: F
authors.lastname: Martinetti
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: T
authors.initials: T
authors.lastname: Seisen
authors.affiliation: Molecular Radiotherapy - UMR1030, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France; Medical Physics, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: D
authors.initials: D
authors.lastname: Lefkopoulos
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: C
authors.initials: C
authors.lastname: Chargari
authors.affiliation: Radiation Therapy, Gustave Roussy Cancer Campus Grand Paris, Villejuif, France.
authors.forename: C
authors.initials: C
authors.lastname: Haie-Meder
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D010388:Pelvis / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D016896:Treatment Outcome; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Cervical cancer; HR-CTV D90; image-guided adaptive brachytherapy; pelvic radiotherapy; planning aims