ESTRO 36 Abstract Book

S70 ESTRO 36 2017 _______________________________________________________________________________________________

that some metastatic patients have a durable survival in case their limited metastases are surgically removed. For these cases, they proposed the term oligometastases, suggesting that eradicating oligometastases with metastasis-directed therapy (MDT) would have the potential to improve survival. This hypothesis would shift the paradigm for oligometastatic patients from a palliative to a potentially curable disease. Recent data in several solid tumors support the notion that patients with oligometastatic disease have a more favorable prognosis as compared to their counterparts and that these different phenotypes probably require a different therapeutic approach. Clinical data indicate that the number of patients with oligometastatic disease receiving aggressive treatment is increasing rapidly. We will discuss the key evidence supporting or refuting the existence of an oligometastatic state. SP-0146 Oligometastatic disease: Radiophysics implementation and pitfalls D. Verellen 1 1 GZA- Ziekenhuizen - St. Augustinus Iridium Kankernetwerk Antwerpen, Radiotherapy, Wilrijk, Belgium As clinical evidence in favor of SBRT for treatment of oligometastatic disease increases, SBRT proves to be a safe and effective treatment modality to achieve local control and delay progression, which in turn also postpones the need for further treatment. Basically SBRT refers to a high-dose-per-fraction-high-precision technique and the mainstream adaptation of SBRT is the result of combined developments in image guided motion management, treatment planning and delivery. This presentation will cover some of the main issues related to clinical implementation of SBRT and quality assurance. A critical overview will be provided comparing dedicated equipment against mainstream technology. The different treatment modalities will be benchmarked allowing to assess an appropriate balance between technological needs and patient compliance. As the efficacy of SBRT in the management of the oligometastic state increases, the need for treatment of multiple metastases and re- irradiation requires extra attention. In this presentation, some of the issues related to dose accumulation for this particularly challenging situation will also be highlighted. SP-0147 Interpretation and management of oligometastases H. Onishi 1 1 Yamanashi University, Department of Radiology, Chuo, Japan All of cancer state with metastases is judged as stage IV even if the number of metastases is only one. However, it has been known that some of patients with a limited number of metastatic lesions regions have a good prognosis by a locally radical therapy combined with systemic chemotherapy, and the disease state was named “oligometastases” by Hellman in 1995. In addition, a limited disease state of oligometastases with primary lesion controlled was named “oligorecurrence” in Japan, and it is considered to have a better survival than “oligometastases with uncontrolled primary site” (synchronous oligometastases, named by Niibe). There are aggressive cancer cells in the primary lesion from the initial state of synchronous oligometastases, so its prognosis is generally poor. In the oligorecurrence state, cancer cells are seeded in the metastatic site at the control of primary lesion, and Interleukin has been reported to play a key role in progression of micrometastases. Locally radical therapy for oligometastases includes surgical resection, radiofrequency ablation, or radiotherapy, and in particular, stereotactic body

radiation therapy (SBRT) is remarked as a promising treatment modality for oligometastases, accompanying not only a high local control rate with a mild toxicity, but also possibility of abscopal effect. In the NCCN guideline for non-small cell lung cancer, it is described that definitive radiotherapy to oligometastases, particularly SBRT, is an appropriate option in such cases if it can be delivered safely to the involved sites. Longer survival would be expected in cases of indolent oligometastatc states such as limited number of metastases and destination organs, metastases to parallel organ, and metachronous or late-onset timing. Though some studies showed good clinical effectiveness of SBRT for patients with oligometastases, further prospective studied are mandatory to address the significance of SBRT for oligometastases and true prognostic factors, and a desirable treatment method according to each kind of primary cancer sites. Recently, drugs for immune checkpoint inhibitor appeared and are expected to have a synergistic effect with radiotherapy to each other, in particular SBRT or particle therapy. Many prospective studies of combined therapy with SBRT and immune checkpoint inhibitors for metastatic disease were just started, but there remains a big problem of high expensive cost of immune checkpoint inhibitors. In this presentation, interpretation and management of oligometastases will be reviewed in order to evaluate and develop the significance of radiotherapy for oligometastases. Stereotactic body radiotherapy (SBRT) is commonly used to treat patients with extracranial oligometastases in clinical settings. In addition, the “abscopal effect”, which is radiotherapy-induced immune-mediated tumor regression at sites distant to the irradiated field, and treatment with a combination of SBRT and immune checkpoint inhibitors have attracted attentions of researchers. According to an international survey of more than 1000 radiation oncologists reported by Lewis SL et al.[1], 61% of responders have been using SBRT for extracranial oligometastases, and the most commonly treated organs were the lung (90%), liver (75%) and spine (70%). Many authors have suggested that surgery for extracranial oligometastases might improve local control and overall survival. With the recent technical developments in SBRT, SBRT is also a promising modality for achieving a high rate of local control with minimal invasiveness. In this lecture, we would like to review the treatment results of SBRT for extracranial oligometastases, such as those located in the lung, liver and spine and discuss comparisons between surgery and SBRT, and cost-effectiveness. 1) SBRT for extracranial oligometastases, such as those located in the lung, liver and spine. 1. Lung Colorectal cancer (CRC) often presents with oligometastases, commonly in the lung and liver, and CRC has a high risk of local failure [2]. The accepted selection criteria include a good performance status (PS), absence of extra-pulmonary disease, control of the primary tumor, 1-5 synchronous or metachronous metastases and adequate respiratory function [3, 4]. Several authors have reported that the 2-year local control rate ranges 49- 96%. The optimal dose is recommended at least 48 Gy in three fractions to achieve greater than 90% 2-year control. 2. Liver The best candidates are patients with a good PS, controlled or absent extra-hepatic disease, ≤3 hepatic lesions, size lesions ≤3 cm, lesion distance from organs at risk >8 mm, good liver function (Childs A) and a healthy liver [5]. Several authors have reported that the 2-year local control rate ranged from 79- 92%.The optimal dose SP-0148 SBRT for oligometastases T. Kimura 1 , Y. Nagata 1 1 Hiroshima University, Department of Radiation Oncology, Hiroshima, Japan