ESTRO38 Congress Report

Brachytherapy

5. Performance of ring versus ovoids and intracavitary versus intracavitary-interstitial in the EMBRACE study (E38-1266) Monica Serban 1,2 , Christian Kirisits 3 , Astrid de Leeuw 4 , Richard Pötter 3 , Ina Jürgenliemk-Schulz 4 , Nicole Nesvacil 3 , Jamema Swamidas 5 , Robert Hudej 6 , Gerry Lowe 7 , Taran Paulsen Hellebust 8 , Geetha Menon 9 , OinamArun 10 , Peter Bownes 11 , Bernard Oosterveld 12 , Marisol De Brabandere 13 , Kees Koedooder 14 , Anne Beate Langeland Marthinsen 15 , Diane Whitney 16 , Jacob Lindegaard 1 , Kari Tanderup 1 , EMBRACE Collaborative Group 1 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; 2 Department of Medical Physics, McGill University Health Centre, Montreal, Canada; 3 Department of Radiation Oncology, Comprehensive Cancer Centre, Medical University of Vienna / General Hospital of Vienna, Vienna, Austria; 4 Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands; 5 Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India; 6 Department of Radiotherapy, Institute of Oncology Ljubljana, Slovenia; 7 Cancer Centre, Mount Vernon Hospital, London, UK; 8 Department of Oncology, The Norwegian RadiumHospital, Oslo University Hospital, Oslo, Norway; 9 Department of Oncology, Cross Cancer Institute, University of Alberta, Edmonton, Canada; 10 Department of Radiotherapy and Oncology, Postgraduate Institute of Medical Education and Research, Chandigarh, India; 11 Leeds Cancer Centre, St James's University Hospital, Leeds, UK; 12Radiotherapiegroep, Arnhem, The Netherlands; 13 Department of Radiation Oncology, UZ Leuven, Belgium; 14 Department of Radiation Oncology Academic Medical Centre, University of Amsterdam, The Netherlands; 15 Department of Radiotherapy, Cancer Clinic, St. Olavs Hospital, and Department of Physics, NTNU, Trondheim, Norway; 16 Oncology Centre, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, UK

Context of the study There is currently a wide variety of applicator designs available for cervix cancer brachytherapy. The Gynecologic Cancer Intergroup survey on international brachytherapy practice patterns reported that the tandem and ovoid (T&O) is the most frequently used applicator in cervix cancer followed by the tandem and ring (T&R). While these applicators were initially used as intracavitary (IC) applications only, recent developments have combined the intracavitary/interstitial (IC/IS) applications in order to improve target coverage for large tumours/unfavourable topography. Therefore, the classical T&R or T&O applicators have been modified and used as a template for needle placement into the parametria. Although the T&O and T&R are currently considered clinically equivalent and no correlations have so far been made in relationship to long-term clinical outcomes, significant dosimetric differences have been reported when using one applicator versus the other. These dosimetric differences have been difficult to interpret due to the multitude of applicator designs, implantation practices, loading/ optimization methods, dose prescription and reporting of procedures. Overview of abstract The present study investigated the effect of applicator (T&R versus T&O) and technique (IC versus IC/IS) on achieved target coverage, isodose surface volumes, bladder, rectum, sigmoid and vaginal doses in patients treated within the EMBRACE-I study. 949 patients treated with T&O and T&R applicators, from 18 centres were analysed. Patients received external beam radiotherapy with concomitant chemotherapy, followed by magnetic resonance image- guided adaptive brachytherapy (MR-IGABT). Centres were divided into 4 groups, according to their applicator and needle usage: T&O-IC and T&R-IC centres treating mainly with the IC technique; T&O-IC/IS and T&R-IC/IS centres treating routinely with the IC/IS technique.

What were the three main findings of your research? Patient characteristics, target and OAR doses for each centre group are presented in Table 1. T&R–IC, as compared to T&O–IC applicators, showed better dose conformity (23% lower V85Gy) for better target dose coverage (∼3 Gy higher for median target volumes). Both IC applicators failed to cover large target volumes. Routine application of IC/IS considerably improved target dose by 5-9 Gy higher for target volumes of 60 cm3 (Figure 1) and reduced OARs doses. Bladder/rectum doses were more favourable (3–9 Gy lower) with T&R-IC compared to T&O-IC while vagina doses were less favourable (17 Gy higher). What impact could your research have? This brachytherapy applicator/technique study, conducted on a large patient cohort, helps improve understanding of the advantages and disadvantages of a particular applicator. It is clear that, depending on how they fit to the normal and pathologic anatomy at the exocervix and vaginal fornices, one applicator can have advantages over another. These results can assist physicians and physicists in their implantation practices as well as optimization and loading methods. In the future, aside from these new dosimetric findings, a comprehensive viewon the IC and IC/IS techniques and T&R/T&O applicators will have to take into account practical considerations and, most importantly, the impact of technique, applicator and dose on disease andmorbidity outcome. Is this research indicative of a bigger trend in oncology? This is the largest study to date that quantifies dosimetric properties of T&O and T&R applicators and IC versus IC/ IS techniques, where overall, the T&R and IC/IS technique appeared to be superior. The insights resulting from this research will be helpful in the design of more sophisticated brachytherapy applicators. In fact, a trend in new applicators is already apparent. A new commercial applicator was designed as a hybrid applicator that combines the advantages of both T&R and T&O applicators and that of the IC/IS technique through the use of both parallel and

BRACHYTHERAPY | Congress report

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