title: Comparison between the ICRU rectal point and modern volumetric parameters in brachytherapy for locally advanced cervical cancer.
abstract: OBJECTIVE
  The implementation of image-guided brachytherapy in cervical cancer raises the problem of adapting the experience acquired with 2D brachytherapy to this technique. The GEC-ESTRO (Groupe européen de curiethérapie - European Society for Radiotherapy and Oncology) has recommended reporting the dose delivered to the rectum in the maximally exposed 2 cm(3) volume, but so far, the recommended dose constraints still rely on 2D data. The aim of this study was to evaluate the relationship between the doses evaluated at the ICRU rectal point and modern dosimetric parameters.
  
  
  METHODS
  For each patient, dosimetric parameters were generated prospectively at the time of dosimetry and were reported. For analysis, they were converted in 2 Gy equivalent doses using an α/β ratio of 3 with a half-time of repair of 1.5 hours.
  
  
  RESULTS
  The dosimetric data from 229 consecutive patients treated for locally advanced cervical cancer was analyzed. The mean dose calculated at ICRU point (DICRU) was 55.75 Gy ± 4.15, while it was 59.27 Gy ± 6.16 in the maximally exposed 2 cm(3) of the rectum (P=0.0003). The D2 cm(3) was higher than the DICRU in 78% of the cases. The mean difference between D2 cm(3) and DICRU was 3.53 Gy ± 4.91. This difference represented 5.41% ± 7.40 of the total dose delivered to the rectum (EBRT and BT), and 15.49% ± 24.30 of the dose delivered when considering brachytherapy alone. The two parameters were significantly correlated (P=0.000001), and related by the equation: D2 cm(3)=0.902 × DICRU + 0.984. The r(2) coefficient was 0.369.
  
  
  CONCLUSIONS
  In this large cohort of patients, the DICRU significantly underestimates the D2 cm(3). This difference probably results from the optimization process itself, which consists in increasing dwell times above the ICRU point in the cervix. Considering these findings, caution must be taken while implementing image-guided brachytherapy and dose escalation.
authors.affiliation: Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France; Laboratoire de radiothérapie moléculaire, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France; Inserm U1030, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France. Electronic address: renaud.mazeron@gustaveroussy.fr.
authors.forename: R
authors.initials: R
authors.lastname: Mazeron
authors.affiliation: Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Kamsu Kom
authors.affiliation: Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: E
authors.initials: E
authors.lastname: Rivin del Campo
authors.affiliation: Département de physique médicale, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: I
authors.initials: I
authors.lastname: Dumas
authors.affiliation: Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: G
authors.initials: G
authors.lastname: Farha
authors.affiliation: Département de physique médicale, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Champoudry
authors.affiliation: Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Chargari
authors.affiliation: Département de physique médicale, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Martinetti
authors.affiliation: Département de physique médicale, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France; Laboratoire de radiothérapie moléculaire, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France; Inserm U1030, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: D
authors.initials: D
authors.lastname: Lefkopoulos
authors.affiliation: Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Haie-Meder
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D016014:Linear Models; D053783:Magnetic Resonance Imaging, Interventional; D058958:Organs at Risk / Q000528:radiation effects*; D011446:Prospective Studies; D015641:Radiography, Interventional; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012007:Rectum / Q000473:pathology / Q000528:radiation effects*; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*
keywords: Brachytherapy; Cancer du col utérin; Cervical cancer; Curiethérapie; ICRU point; Point de l’ICRU; Rectum