E. Lartigau

Accelerated partial breast irradiation using robotic radiotherapy: a dosimetric comparison with tomotherapy and three-dimensional conformal radiotherapy.

BackgroundAccelerated partial breast irradiation (APBI) is a new breast treatment modality aiming to reduce treatment time using hypo fractionation. Compared to conventional whole breast irradiation that takes 5 to 6xa0weeks, APBI is reported to induce worse cosmetic outcomes both when using three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). These late normal tissue effects may be attributed to the dose volume effect because a large portion of the non-target breast tissue volume (NTBTV) receives a high dose. In the context of APBI, non-coplanar beams could spare the NTBTV more efficiently. This study evaluates the dosimetric benefit of using the Cyberknife (CK) for APBI in comparison to IMRT (Tomotherapy) and three dimensional conformal radiotherapy (3D-CRT).MethodsThe possibility of using surgical clips, implanted during surgery, to track target movements is investigated first. A phantom of a female thorax was designed in-house using the measurements of 20 patients. Surgical clips of different sizes were inserted inside the breast. A treatment plan was delivered to the mobile and immobile phantom. The motion compensation accuracy was evaluated using three radiochromic films inserted inside the breast. Three dimensional conformal radiotherapy (3D-CRT), Tomotherapy (TOMO) and CK treatment plans were calculated for 10 consecutive patients who received APBI in Lille. To ensure a fair comparison of the three techniques, margins applied to the CTV were set to 10xa0mm. However, a second CK plan was prepared using 3xa0mm margins to evaluate the benefits of motion compensation.ResultsOnly the larger clips (VITALITEC Medium-Large) could be tracked inside the larger breast (all gamma indices below 1 for 1xa0% of the maximum dose and 1xa0mm). All techniques meet the guidelines defined in the NSABP/RTOG and SHARE protocols. As the applied dose volume constraints are very strong, insignificant dosimetric differences exist between techniques regarding the PTV coverage and the sparing of the lung and heart. However, the CK may be used to reduce high doses received by the NTBTV more efficiently.ConclusionsRobotic stereotactic radiotherapy may be used for APBI to more efficiently spare the NTBTV and improve cosmetic results of APBI.

Harmonization of the Volume of Interest Delineation among All Eleven Radiotherapy Centers in the North of France.

Background Inter-observer delineation variation has been detailed for many years in almost every tumor location. Inadequate delineation can impair the chance of cure and/or increase toxicity. The aim of our original work was to prospectively improve the homogeneity of delineation among all of the senior radiation oncologists in the Nord-Pas de Calais region, irrespective of the conditions of practice. Methods All 11 centers were involved. The first studied cancer was prostate cancer. Three clinical cases were studied: a low-risk prostate cancer case (case 1), a high-risk prostate cancer case (pelvic nodes, case 2) and a case of post-operative biochemical elevated PSA (case 3). All of the involved physicians delineated characteristically the clinical target volume (CTV) and organs at risk. The volumes were compared using validated indexes: the volume ratio (VR), common and additional volumes (CV and AV), volume overlap (VO) and Dice similarity coefficient (DSC). A second delineation of the same three cases was performed after discussion of the slice results and the choice of shared guidelines to evaluate homogenization. A comparative analysis of the indexes before and after discussion was conducted using the Wilcoxon test for paired samples. A p-value less than 0.05 was considered to indicate statistical significance. Results The indexes were not improved in case 1, for which the inter-observer agreement was considered good after the first comparison (DSC = 0.83±0.06). In case 2, the second comparison showed homogenization of the CTV delineation with a significant improvement in CV (81.4±11.7 vs. 88.6±10.26, respectively, p = 0.048), VO (0.41±0.09 vs. 0.47±0.07, respectively; p = 0.009) and DSC (0.58±0.09 vs. 0.63±0.07, respectively; p = 0.0098). In case 3, VR and AV were significantly improved: VR: 1.71(±0.6) vs. 1.34(±0.46), respectively, p = 0.0034; AV: 46.58(±14.50) vs. 38.08(±15.10), respectively, p = 0.0024. DSC was not improved, but it was already superior to 0.6 in the first comparison. Conclusion Our prospective work showed that a collaborative discussion about clinical cases and the choice of shared guidelines within an established framework improved the homogeneity of CTV delineation among the senior radiation oncologists in our region.

BioPro-RCMI-1505 trial: multicenter study evaluating the use of a biodegradable balloon for the treatment of intermediate risk prostate cancer by intensity modulated radiotherapy; study protocol

BackgroundProspective trials have demonstrated the advantage of dose-escalated radiotherapy for the biochemical and clinical control of intermediate risk prostate cancer. Dose escalation improves outcomes but increases risks of urinary and bowel toxicity. Recently the contribution of “spacers” positioned in the septum between the rectum and the prostate could improve the functional results of intensity modulated radiation therapy (IMRT). To date most of the evaluated devices were polyethylen glycol (PEG) and hyaluronic acid (HA). Men on the Spacer arm had decreased bowel toxicity and less decline in both urinary and bowel quality of life as compared to Control men in a randomized trial.MethodsThis is an interventional, multi-center study to evaluate the use of biodegradable inflatable balloon for patients with intermediate risk prostate cancer treated by IMRT (74 to 80xa0Gy, 2xa0Gy/fraction) with daily image guided radiotherapy.DiscussionThis multicenter prospective study will yield new data regarding dosimetric gain and implantation stages of Bioprotect balloon. Acute and late toxicities and quality of life will be registered too.Trial registrationNCT02478112, date of registration: 15/06/2015.

Harmonisation de la délinéation des volumes d’intérêt entre les centres de radiothérapie de la région Nord-Pas-de-Calais

Objectifs Comparer et harmoniser les pratiques de delineation entre les centres de radiotherapie de la region Nord-Pas-de-Calais. Materiels et methodes La totalite des onze centres de radiotherapie de la region participe a ce travail finance par le conseil regional du Nord-Pas-de-Calais, des fonds europeen de developpement regional (Feder), des missions d’interet general (MIG), de la Ligue contre le cancer, des centres eux-memes, et pilote par le Reseau regional de cancerologie. Les localisations concernees sont les cancers de la prostate, des voies aerodigestives superieures et du sein. Nous presentons ici les premiers resultats concernant le cancer prostatique. Apres un choix commun de referentiels publies, trois cas cliniques anonymises ont ete envoyes a chaque centrexa0: cancer prostatique de bas risque (cas 1), de haut risque (aires pelviennes, cas 2), loge de prostatectomie (cas 3). Chaque centre devait renvoyer au moins un contour (volume cible anatomoclinique et organes a risque) pour chacun des cas cliniques avec la console P2E (Aquilab SAS). Les quatorze delineations ont ete comparees grâce a des indices validesxa0: volumes absolus, rapport de volumes, indice de Dice ou Kappa, Volume Overlap (VO), volume commun delinee, volume supplementaire delinee. Les resultats ont ete discutes lors des reunions de l’association loi 1901 des oncologues-radiotherapeutes du Nord (Cronor), a l’initiative du projet. Une deuxieme delineation a ete realisee pour les memes cas. L’harmonisation a ete evaluee par l’amelioration des indices (test de Wilcoxon sur series appariees). Resultats La premiere comparaison a montre des resultats juges satisfaisants pour le cas 1 (rapport de volumes de 1,16xa0±xa00,26, volume overlap de 0,71xa0±xa00,08, indice Kappa de 0,83xa0±xa00,05) et statistiquement superieurs aux autres cas (pxa0 Conclusion Notre travail collaboratif a permis une discussion et une harmonisation des pratiques de delineation de l’ensemble des praticiens a l’echelle regionale.