A margin-of-the-day online adaptive intensity-modulated radiotherapy strategy for cervical cancer provides superior treatment accuracy compared to clinically recommended margins: A dosimetric evaluation

Abstract

(2013) A margin-of-the-day online adaptive intensity-modulated radiotherapy strategy for cervical cancer provides superior treatment accuracy compared to clinically recommended margins: A dosimetric evaluation, Acta Oncologica, 52:7, 1430-1436 Abstract Purpose. To dosimetrically evaluate a margin-of-the-day (MoD) online adaptive intensity-modulated radiotherapy (IMRT) strategy for cervical cancer patients. The strategy is based on a single planning computed tomography (CT) scan and a pretreatment constructed IMRT plan library with incremental clinical target volumes (CTV)-to-planning target volumes (PTV) margins. Material and methods. For 14 patients, 9 -10 variable bladder fi lling CT scans acquired at pretreatment and after 40 Gy were available. Bladder volume variability during the treatment course was recorded by twice-weekly US bladder-volume measurements. A MoD strategy that selects the best IMRT plan of the day from a library of plans with incremental margins in steps of 5 mm was compared with a clinically recommended population-based margin (15 mm). To compare the strategies, for each fraction that had a recorded US bladder-volume measurement, the CT scan with the nearest bladder volume was selected from the pretreatment CT series and from the CT series acquired after 40 Gy. A frequency-weighted average of the dose-volume histograms (DVH) parameters calculated for the two selected CT scans was used to estimate the DVH parameters of the fraction of interest. Results. The 15-mm recommended margin resulted in cervix-uterus underdosage in six of 14 patients. Compared with the 15-mm margin, the MoD strategy resulted in signifi cantly better cervix-uterus coverage (p ϭ 0.008) without a signifi cant difference in the sparing of rectum, bladder, and small bowel. For each patient, 3 -8 (median 5) plans were needed in the library of plans for the MoD strategy. The required range of the MoD was 5 -45 mm (median 15 mm). Twenty-fi ve percent of all fractions could be treated with a MoD of 5 mm and 81% of all fractions could be treated with a MoD up to 25 mm. Conclusions. Compared with a clinically recommended margin, a simple online adaptive strategy resulted in better cervix-uterus coverage without compromising organs at risk sparing.

Dosimetric advantages of a clinical daily adaptive plan selection strategy compared with a non-adaptive strategy in cervical cancer radiation therapy

“…Previously conducted research on cervical cancer ART focused either on the quantification of inter-and intrafraction anatomical changes [11], the optimization of various adaptive strategies [9,10,21], tools to guide or automate adaptive workflows [12,13] or the clinical implementation [7]. However, the actual benefit of ART in terms of delivered dose while taking into account day-to-day anatomical variations is essential to further improve current adaptive strategies.…”

“…Furthermore, these large safety margins increase the dose to surrounding healthy tissues, which results in the enhancement of radiation-induced toxicity. Recently, several adaptive strategies in cervical cancer were investigated to anticipate on anatomical changes during the course of RT [9,10]. Next to the description of a clinically implemented adaptive strategy [7], most studies reported on tools to support or automate adaptive workflows [9,[11][12][13].…”

Adaptive radiotherapy strategies for pelvic tumors – a systematic review of clinical implementations

“…In addition to one in silico implementation of online compensation [58], these were the only studies where feedback from delivered dose triggered adaptations. Contributing to differences in applied strategies and workflows could be the additional manual contouring, which was a pre-requisite in over 70% of the simulated ART workflows [22,59,60,[62][63][64][65][66][68][69][70]72,74,78,79,[81][82][83]85,86,88,89,91,93,[95][96][97][98][100][101][102][103][104][105][106][107]. To reduce the need of manual contours, the segmentation could be propagated using deformable image registration.…”

Bénéfice de la radiothérapie adaptative par bibliothèque de plans de traitement pour les cancers du col utérin ?

“…Ces variations anatomiques exposent, de ce fait, les patientes à un risque de surdosage des organes à risque et donc de toxicité, et de « sous-dosage » du volume cible et donc de récidive. La prise en compte classique et historique de ces variations anatomiques implique de larges marges autour du volume cible anatomoclinique (de l'ordre de 15 mm [9,10]) sur une seule planification initiale, exposant ainsi à une irradiation importante des organes à risque. Une autre stratégie corrective très novatrice est une radiothérapie adaptative basée sur une bibliothèque de plans de traitement et l'utilisation de tomographies coniques (cone beam computed tomography [CBCT]).…”