Abstract book - ESTRO meets Asia

S39 ESTRO meets Asia 2018

Imaging: Imaging is another important component of the IGABT. MR Image guidance is the gold standard imaging. In India, access to MRI for BT planning is a major constraint. 2D radiographic localization is still widely used, however, new radiotherapy centers are installing CT simulators, which is being increasingly used for both external RT and BT. In order to mitigate the repetitive use of MR, alternatives like MRI at first BT-application, and CT in subsequent treatments have been explored. There has also been ongoing research for various imaging modalities which could be adapted in different environments. Volume delineation: GYN GEC ESTRO recommendations which were published in 2004 describe the concepts and terms used in IGABT using MRI images. Alternatively, CT image-based contouring and its correlation with MRI/US also has been explored which needs careful adaptation and further research. Contouring has been shown to be associated with significant uncertainties; therefore, training and education is vital. Applicator reconstruction: Applicator reconstruction accuracy using different imaging modalities also forms a vital step in the planning process, which mandates applicator commissioning using different imaging modalities, which include characterization of the artifacts produced in MRI by various applicators, especially when using Ti needles, so that they can be taken care appropriately at the time of the applicator reconstruction. Treatment planning / optimization: With the introduction of inverse planning algorithms for BT, physicists have often been misled that it results in better plans as compared to standard manual optimized plans. The current practice is to start with a standard loading pattern based on institutional practice, normalized to point-A, followed by manual dose optimization to achieve optimal doses to target and OARs. Graphical optimization can be used, however, with caution especially for IC+IS applications, where, the loading of the IS needles is restricted to less than 25% so that, major part of the dose is delivered from the IC applicator and the high dose region remains around the utero-cervical canal/GTV. To optimally use the resources, delivery of two fractions, one, on the day of the implantation and the other, on the next day morning can be done, which is practiced in many centers. . Inter-intra fraction variation: In fractionated BT applications, inter/intra fraction variation understanding is also important. Our research on inter application variation of the spatial location of 2cm3 volumes revealed that the applications/fractions are quite stable in topography for bladder and rectum, and hence the current practice of cumulative addition of D2cm3 dose is valid for bladder and rectum, may not be for sigmoid. Conclusion :MR IGABT approach being gold standard, is associated with major challenges in implementation in LMIC’s including India/Asia. A systematic roadmap and approach usually leads to a smooth transition from 2D to 3D IGABT. Apart from training and education, appropriate utilization of applicators, Imaging and reducing uncertainties involved in various processes is vital. Alternative imaging like CT /US needs more research. Treatment planning processes especially applicator commissioning, reconstruction and plan optimization is associated with a learning curve. The clinical outcome of MR IGABT in resource constraint setting from India has been enterprising.

distribution both the anatomy (target volume/organs at risk) and the applicator(s) should be correctly localised in the images. If the image modality does not enables both of these criteria the dose delivered the patient may be calculated incorrectly. Another important aspect is that the images should reflect the true situation at the time of the treatment. Due to the large dose gradient in brachytherapy, even small changes in the position of the applicator and/or anatomical structures may lead to discrepancies between planned and delivered dose. Usually, this is achieved with as short time as possible between imaging and treatment delivery. In-room imaging is implemented in several brachytherapy centres worldwide. The varicose guidelines also recommend terms and terminology to be used for dose assessment and reporting. In radiotherapy in general it is essential to use a common language in order to compare clinical results from different centres worldwide. When applying IGBT it is important to use a terminology adjusted to the complex nature of such treatment technique. Preferably the same terminology should be used for different brachytherapy sites. It should also be harmonized, as far as possible, to the terminology used in external beam radiotherapy, e.g. ICRU 83. SP-100 RTT Experience - Head and neck Brachytherapy in Indian scenario A. Sridhar 1 , 1 NIMS Hyderabad, India 1 Tata Memorial Hospital, Medical Physics, Mumbai, India 2 Tata Memorial Hospital, Radiation Oncology, Mumbai, India Abstract text MR Image Guided Adaptive Brachytherpay (IGABT) has shown promising results in terms of local control and decrease in toxicities. This approach is becoming increasingly popular not only in the western countries but also in other parts of the world. However, its implementation in Asia including India has been challenging. Various challenges which need to be addressed have been discussed in the following sections. Training and Education: For decades, conventional BT practice has been utilized in LMIC’s including India, however, there has been hardly any major attempts towards refinement and developments in this field. So, there has been a major gap in knowledge, attitudes and practices for management of cervical cancer. In order to make a change, training and education of every process including applicator selection, insertion, imaging, contouring, applicator reconstruction, dose optimization and evaluation is vital. We, at Tata Memorial Hospital, Mumbai India, took an initiative of implementing IGABT in a structured program by undertaking a bilateral exchange program with Medical University, Vienna, Austria. Applicators: One of the major limitations of implementation of IGABT is the lack of advanced GYN BT Applicators, which are expensive as compared to conventional IC applicators. Conventional applicators produce artifacts in CT, which makes the CT anatomy difficult to visualize. Furthur, they are limited in delivering adequate doses to advanced residual disease at BT. Abstract not received SP-101 Challenges in implementing Image Based Adaptive Brachytherapy for Gynaecological cancers in India (Asia): Physicist Perspective J. Swamidas 1 , U. Mahantshetty 2

Teaching lecture: High tech technologies

SP-102 Bone marrow sparing in whole pelvic radiotherapy P. Franco 1 1 University of Turin, Department of Oncology- Radiation Oncology, Turin, Italy