Three-dimensional Analysis of Recurrence Patterns in Rectal Cancer: The Cranial Border in Hypofractionated Preoperative Radiotherapy Can Be Lowered

J. Nijkamp, M. Kusters, R.G.H. Beets-Tan, H. Martijn, G.L. Beets, C.J. van de Velde, C.A. Marijnen

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Abstract

PURPOSE: The aim of this study was to determine whether and where the radiotherapy (RT) clinical target volume (CTV) could be reduced in short-course preoperative treatment of rectal cancer patients. METHODS AND MATERIALS: Patients treated in the Dutch total mesorectal excision trial, with a local recurrence were analyzed. For 94 (25 who underwent radiation therapy 69 who did not) of 114 patients with a local recurrence, the location of the recurrence was placed in a three-dimensionalthree (3D) model. The data in the 3D model were correlated to the clinical trial data to distinguish a group of patients eligible for CTV reduction. Effects of CTV reduction on dose to the small bowel was tested retrospectively in a dataset of 8 patients with three-field conformal plans and intensity-modulated RT (IMRT). RESULTS: The use of preoperative RT mainly reduces anastomotic, lateral, and perineal recurrences. In patients without primary nodal involvement, no recurrences were found cranially of the S2-S3 interspace, irrespective of the delivery of RT. In patients without primary nodal involvement and a negative circumferential resection margin (CRM), only one recurrence was found cranial to the S2-S3 interspace. With a cranially reduced CTV to the S2-S3 interspace, over 60% reduction in absolute small bowel exposure at dose levels from 15 to 35 Gy could be achieved with three-field conventional RT, increasing to 80% when IMRT is also added. CONCLUSIONS: The cranial border of the CTV can safely be lowered for patients without expected nodal or CRM involvement, yielding a significant reduction of dose to the small bowel. Therefore, a significant reduction of acute and late toxicity can be expected.
Original languageEnglish
Pages (from-to)103-110
Number of pages8
JournalInternational Journal of Radiation Oncology Biology Physics
Volume80
Issue number1
DOIs
Publication statusPublished - 1 May 2011

Keywords

  • Rectal cancer recurrence
  • CTV reduction
  • Recurrence patterns
  • Organs at risk
  • Dose reduction
  • TOTAL MESORECTAL EXCISION
  • DOSE-VOLUME RELATIONSHIP
  • SMALL-BOWEL TOXICITY
  • RADIATION-THERAPY
  • PELVIC IRRADIATION
  • HIGH-RESOLUTION
  • RESECTION MARGIN
  • RANDOMIZED-TRIAL
  • LOCAL RECURRENCE
  • BELLY BOARD

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