ESTRO 37 Abstract book

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ESTRO 37

7 Mount Vernon Hospital, Mount Vernon Centre for Cancer Treatment, Middlesex, United Kingdom Purpose or Objective The EMBRACE study (www.embracestudy.dk) includes treatment and clinical outcome data of patients with locally advanced cervical cancer from 23 centers who were treated with radiochemotherapy (EBRT and MRI- guided brachytherapy (IGBT)), between 2008 and 2016. The aim of this investigation is to study the implementation of the IGBT technique based on a variety of institutional protocols in EMBRACE, in comparison with expected dosimetric results for the future prospective dose EMBRACEII study, which applies advanced image- guided EBRT and BT through a specific prescription protocol. Material and Methods 1304 patients were included in this analysis. Total treatment dose for CTV HR and organs at risk (OARs) was calculated using the linear quadratic model for biologically equivalent dose (EQD2) using a/b=3Gy for OARs, and a/b=10Gy for CTV HR . Results were compared to specific hypotheses on technique, doses and volumes defined in the EMBRACEII protocol (Tab.1, col.1) as well as to an intermediate EMBRACE study report from the time of EMBRACEII protocol development (2014/15), cited in the study protocol. (Tab.1, col.2). Patients were grouped by volumes of CTV HR ≤/> 30cm³ for investigation of the frequency of the use of intracavitary (ic) or intracavitary+interstital (ic/is) application techqniques and the fraction of cases with CTV HR D 90 >85Gy 10 . For the whole cohort, the fraction of cases with total D 2cm³ <80Gy 3 (bladder) and <65Gy 3 (rectum) were calculated and compared to the fraction of patients expected to stay below these doses for EMBRACEII. Vaginal dose was evaluated based on the mean fraction of the total reference air kerma delivered by the vaginal applicator (ring or ovoid) and the fraction of cases with total doses to the rectovaginal ICRU point (ICRU RV) <65Gy 3 was calculated. Results The difference between the status of EMBRACE at the time of development of the EMBRACEII protocol and the current analysis of the complete EMBRACE cohort (Tab. 1), indicates an increased use (~10%) of interstitial applicators for large CTV HR volumes, to reach high prescribed D 90 doses, towards the end of the EMBRACE accrual period. The use of ic/is applicators and the fraction of patients treated with CTV D 90 >85Gy 10 was 7/10% below the aim of the EMBRACE-II protocol, for small/large volumes. EMBRACE-II dose constraints for D 2cm³ were fullfilled by nearly the same fraction of EMBRACE patients (difference 2-3%) as aimed for in the future trial. Mean vaginal loading was 13% higher in EMBRACE than the aim of EMBRACE-II. Conclusion During the last years, an increasing understanding of the correlation of dose and outcome in image-guided (adaptive) brachytherapy has emerged. This is continuously driving an evolution of the IGABT practice, and eventually the EMBRACE II protocol has been launched with hypotheses reflecting the most recent clinical evidence. During EMBRACE-I, ic/is applicators have increasingly been used, and dose to CTV HR and Organs at risk has improved over time.

SP-0261 How can brachytherapy compete with surgery and external irradiation or are these techniques complementary? C. Chargari 1 , H. Martelli 2 , F. Guérin 2 , C. Haie-Meder 3 1 Institut Gustave Roussy, Radiation Oncology, Villejuif, France 2 CHU Kremlin Bicêtre, Pediatrics Surgery, Kremlin Bicêtre, France 3 Gustave Roussy, Radiation Oncology, Villejuif, France Abstract text Treatment modalities of children with malignancies are chosen in order to achieve high cures rates but also to minimize the risk of definitive sequelae. Radical surgical approaches have been now replaced by conservative treatments involving radiotherapy as part of a multimodal strategy. In this context, brachytherapy has been used in few specialized centers as part of the treatment of patients with rhabdomyosarcoma (RMS), based on the dosimetric advantages of this technique and in an attempt to avoid the long-term side effects of external beam radiotherapy. The management of bladder prostate RMS is an appropriate example of how do surgery and brachytherapy complete each other. In selected bladder prostate RMS, it has been shown that a multimodal strategy based on a conservative surgery combined with brachytherapy of the prostate and bladder/neck was effective for ensuring high cures rates at the expanse of acceptable morbidity rates. The surgery consists of a partial cystectomy and/or partial prostatectomy preserving the muscular layer of the trigone and the urethra. Implantation of plastic tubes is conducted peri- operatively through a transperineal approach, with four single leader plastic tubes encompassing the prostate and bladder neck. A ureteral reimplantation and testicular transposition are performed to decrease the risk of ureteral stenosis and to preserve fertility, respectively. Brachytherapy and surgery can be also clearly complementary in the management of gynecological RMS, and the choice of the optimal treatment relies on an estimate of the best therapeutic ratio, to spare fertility. In soft tissues sarcoma surgically treated, the perioperative placement of plastic tubes gives the possibility to have an accurate determination of the volume to be irradiated in case of positive surgical margin. Brachytherapy can also complete with external irradiation. Indeed, brachytherapy is a very appropriate technique for delivering a boost to the primary site when there is regional lymph node extension, or in case brachytherapy should not be given as only treatment because of tumor bulk or because of a too high risk of complication (e.g.: anal RMS). Altogether, these examples illustrate that brachytherapy should be still considered as the best irradiation modality in these selected patients, and that neither surgery nor external irradiation should be seen as competitive, but rather as complementary to give the highest probability of cure with acceptable morbidity. SP-0262 RTT specific role in brachytherapy for young children J. Wilkes 1 1 Academic Medical Center, radiotherapy Brachytherapy, Amsterdam, The Netherlands Abstract text This lecture will highlight the intensive procedure of treating (young) children with a carcinoma for several days with brachytherapy as well as which preconditions are required for this treatment. Since 1993, a multidisciplinary procedure has been developed in our department for the treatment of tumors in children with chemotherapy, surgery and brachytherapy. This procedure is called AMORE which consists of consecutive Ablative surgery, MOuld technique with after loading brachytherapy and immediate surgical REconstruction

Joint Symposium: ESTRO-PROS: Is there a reason not to deliver all curative paediatric treatments with brachytherapy or protons?