Abstract book - ESTRO meets Asia

S16 ESTRO meets Asia 2018

Teaching lecture: Tumour radiobiology and kinetics

Impetus to further reduce radiotherapy volumes was based on 1. the increasing efficacy of systemic therapy which offered high cure rates as a single modality; 2. growing concern about the late effects of even IFRT; 3. improved imaging - particularly PET; 4. improvements in radiotherapy planning and delivery The EORTC group published guidelines for involved node radiotherapy (INRT) which strictly limits fields/treated volumes to sites of macroscopic disease evident prior to chemotherapy (adjusting for anatomical shifts), with the assumption that chemotherapy adequately controls both systemic and regional microscopic disease. INRT has been shown to be effective in retrospective studies for HL, and recently in a prospective study EORTC H10, for early stage favourable and unfavourable HL. INRT has been shown to significantly reduce normal tissue dose compared to IFRT, and is anticipated to reduce late toxicity based on risk modelling. The combination of INRT with advanced treatment techniques such as IMRT and DIBH may further reduce toxicity, though in some setting the use of INRT may lessen the requirement for such techniques. INRT is highly demanding technically and in settings where pre-chemotherapy imaging is suboptimal, or where transferring volumes to planning CT is difficult, the more generous involved site radiotherapy (ISRT) should be used. ISRT has now been recommended as standard of care for other lymphoma subtypes, in particular early stage DLBCL following effective chemotherapy, analogous to early stage HL. IROLG has published a set of guidelines dealing with the application of the ISRT concept in a range of clinical settings. Is should be recognised that the application of INRT/ISRT was developed for early stage HL for which systemic therapy reliably eradicates microscopic regional disease. Other clinical settings raise additional considerations: 1. For indolent lymphomas (Follicular lymphoma, marginal zone lymphoma, nodular lymphocyte predominant HL) often treated with radiotherapy alone, adequate control of regional microscopic disease may still require more generous fields than strict INRT. 2. In settings where the efficacy of chemotherapy is less certain (residual disease post chemotherapy, salvage therapy, inadequate delivery of chemotherapy due to patient frailty) the volume at risk of harbouring residual microscopic disease may also be less certain, so consideration may be given to using more generous fields on an individualised basis. In all cases, the risk of late toxicity (related to patient age, gender and disease location) will be taken into account in weighing up the risks/benefits of expanding treatment volumes beyond INRT. 3. Extra-nodal lymphomas have unique patterns of locoregional spread, and ISRT will often involve coverage of an entire organ (eg stomach, brain), or compartment (orbit, paranasal sinuses) rather than bein limited to a site of macroscopic disease. Finally, in the continued effort to obtain the benefits of radiotherapy with toxicity minimisation, consideration will sometimes be given to reducing the volume to less than ISRT. This is already the case with advanced stage disease treated with full-dose chemotherapy, where by definition all pre-chemo sites are not treated. It may be considered in highly selected patients, such as those with extensive stage II mediastinal lymphoma where, despite optimal advanced planning techniques, inclusion of all pre-chemotherapy sites may lead to unacceptable toxicity risk. Volumes less than ISRT (such as residual volume radiotherapy) are being evaluated in ongoing clinical trials.

SP-042 Tumor radiobiology and kinetics A. Potter 1 1 Royal Adelaide Hospital, Radiation Oncology Department Adelaide, Australia

Abstract not received

Proffered papers: IGRT and treatment verification (RTT)

OC-043 Development of the twist-correction system for radiotherapy of head and neck cancer patients H. Shimizu 1,2 , K. Sasaki 2 , T. Aoyama 1 , S. Matsushima 3 , T. Isomura 1 , T. Kitagawa 1 , H. Fukuma 4 , H. Tachibana 1 , T. Kodaira 1 1 Aichi Cancer Center Hospital, Department of Radiation Oncology, Nagoya, Japan 2 Gunma Prefectural College of Health Sciences, Graduate School of Radiological Technology, Maebashi, Japan 3 Aichi Cancer Center Hospital, Department of Diagnostic and Interventional Radiology, Nagoya, Japan 4 Nagoya City University Hospital, Department of Radiology, Nagoya, Japan Purpose or Objective Intensity modulated radiotherapy can deliver the dose to tumor lesions locally, and reduce the delivery dose to normal tissue surrounding the tumor. However, we often experience a misalignment of the tumor shape by the twist of the patient’s neck region. The correction by the current image-guided system allows to be applied for six axes, but the twist of the patient cannot be canceled completely. The aim of this study was to propose the concept that could correct the twist of the patient, and was to develop a prototype. In addition, we evaluated the operation accuracy of the prototype system of this concept under no-load. Material and Methods The prototype system is shown in Fig. 1. Two plates of different size (A and B) were connected by a fulcrum. Each plate rotates around the fulcrum by adjusting the screws under the plate. The circles in Fig.1 show the angle adjusting screw’s position. The screws that instructed by the filled and empty circles move to the right-left and anterior-posterior directions, respectively. Each angle is calculated by the travel distance of the screw and the known distance between the screws as follow: where, θ i pitch show the pitch, roll, and yaw angles of plate i (A or B) and d indicates the travel distance of the screw. When i is A, d(i p ) shows the travel distance of the screw of A S , and when i is B, d(i p ) shows it of the screw of B I . The clockwise direction for each translation axis was defined as positive angle. First, after all screws were set to the zero position, the rotation angle of each plate was measured by the digital goniometer (DG) and moved randomly. Reproducibility was evaluated by ten repetitive measurements. Next, the combinations of twenty patterns for the screws were given using a random number from Microsoft Excel 2010. To confirm the rotational accuracy of the prototype system, θ i pitch , θ i roll , and θ i yaw calculated at the given travel distance were compared with those measured by the DG. , θ i roll , and θ i yaw