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 language | English |
---|---|
Pages (from-to) | 103-110 |
Number of pages | 8 |
Journal | International Journal of Radiation Oncology Biology Physics |
Volume | 80 |
Issue number | 1 |
DOIs | |
Publication status | Published - 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