ESTRO 37 Abstract book

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ESTRO 37

individuals. Seed loss was defined as the number of seeds on CT being lower than the number of seeds on the X-ray. Results Seed loss was scored in 7 patients (2,2%) with a total of 8 seeds (0.04%) lost between X-ray and CT (see figure 1) • In 2 patients one seed was lost. In both cases the seed was not found by survey of the treatment room, the ward, or an extra survey scan of the lungs of the patient. It was concluded that the seeds migrated out of the prostate, but were still within the patient.

regards to overall survival. A possible hint for a benefit could be derived from surgical series of lung and liver metastases indicating worse overall survival after microscopic incomplete resection compared to complete resection, indicating the need for local control of the respective metastases. Besides, no clear definition of oligo-metastases exists. Currently, a maximum number of lesions and/ or organs involved are proclaimed to define this state, although no standardized agreement exists. In addition, a distinction between synchronous and metachronous oligo-metastatic situation as well as oligo-progression has to be made to fully cover a wide spectrum of biological behaviours. Due to technological innovations and based on positive experiences with treating primary non-small cell lung cancer patients, SBRT is increasingly adopted in the oligo-metastatic situation. Retrospective series, especially including pulmonary and hepatic metastases, report favorable outcome and reasonable toxicity profile. Recently, two prospective studies in oligo-metastatic lung cancer have shown superior progression-free survival with a strategy including vigorous treatment of all metastatic sites with radiotherapy. The current presentation will focus on a) the biology and definition of oligo-metastases and its different presentations, b) the rational of intensified local treatment, c) the role of SBRT and ideas to include knowledge of dose-response analyses in the decision- making process and d) current and future study activities that may answer some of the raised questions in the near future and finally, e) the possible expansion of SBRT in non-oligometastatic stage IV disease in the light of immunotherapy. SP-0373 Planning and delivery strategies for oligometastatic disease P. Kroon 1 1 UMC Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands Abstract text Treatments of oligometastases with stereotactic radiotherapy are becoming a common approach. The published studies show promising results with high rates of local control and a potential postponement of systemic therapy. Early results indicate that treatment related morbidity is limited. A striking aspect is that different centers report use of a variety of treatment planning and delivery strategies. The content of this lecture will be based mainly on peer reviewed papers supported with data from our institution. The topics will cover aspects of treatment planning and image guided treatment. Special focus will be on treatment of lymph node oligometastases. SP-0374 Protons for oligometastases? M. Hoyer 1 , J.B. Petersen 2 1 Hoyer Morten, Danish Center for Particle Therapy, Risskov, Denmark 2 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus N, Denmark Abstract text Photon based stereotactic radiotherapy is the accepted standard radiation modality in therapy of metastases in the brain (SRT) or body (SBRT) and it is widely used for treatment of patients with one or few metastases. In most cases, the metastases are small and not located in close proximity to critical organs at risk. SRT and SBRT can therefore be employed with high doses and a low risk of complication. Protons have superior physical properties with distinct range and dose deposit in the normal tissue and they are often quoted to be more precise than photons. Pencil beam scanned protons may allow very conformal dose distribution. There are,

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In 1 patient, 2 seeds were found in the urine prior to discharge. These seeds were recovered. In 3 patients, 1 seed was lost according to the CT. However, in these 3 cases the lost seed was found upon reconstruction in the TPS. 1 seed was embedded within an implantation needle. This seed was overlooked on the X-ray. On CT the seed loss was detected and the seed was recovered from the implantation needle. An incident report was written and after this event each X-ray is double checked by two RTT’s (previously one). For the following 132 patients, only one seed in one patient seemed lost on CT, however this seed was found upon reconstruction in the TPS.

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fig 1. Conclusion Only 8 out of 20462 implanted seeds were lost at the day of implant. In 2 cases it was concluded that seeds had migrated in the body, 6 seeds were recovered. In only one case CT contributed to seed recovery. Therefore, it was concluded that the CT scan is no longer necessary for seed counting or seed recovery and that X- ray just after implantation and careful survey before discharge of the patient are sufficient. SP-0372 Oligometastases and Oligoprogression: Evidence for local treatment in metastatic disease N. Andratschke 1 1 University Hospital Zürich, Department of Radiation Oncology, Zurich, Switzerland Abstract text Although Hellman and Weichselbaum coined the concept of oligo-metastases as a distinct state with its own biology in 1995, it only recently started to be more thoroughly investigated in the context of stereotactic body radiation therapy (SBRT). Nevertheless, up until now, there is no unequivocal clinical proof that oligo-metastatic patients really do benefit from local interventions such as surgery, interventional radiology or radiotherapy (SBRT) with Symposium: Oligometastatic disease