ESTRO 2020 Abstract book

S75 ESTRO 2020

of CRPC With the recent demonstration that prostate radiotherapy in low volume metastatic disease, further questions arise: Should we treat the prostate only (as in STAMPEDE) or treat prostate plus nodes? Should we also treat the low volume metastases with stereotactic radiotherapy? Can we substitute surgery for radiotherapy? Finally, we know from the control arms of STAMPEDE and the other trials in hormone sensitive disease that many men will get prolonged survival on ADT alone and thus any additional therapy adds potential morbidity and also cost. A reliable way to identify these men would help reduce overtreatment. SP-0141 Radiation therapy in hormone sensitive oligometastatic patients: a step towards cure? P. Blanchard 1 1 Institut Gustave Roussy, Radiation Oncology, Villejuif, France Abstract text With the advancement of treatment for prostate cancer (for surgery, systemic treatments and radiotherapy) and the use of advanced imaging modalities, the number of oligometastatic prostate cancer patients is expected to increase in the coming years. By combining new generation systemic therapies with ablative local treatment to all sites of gross disease, one could aim to cure a significant proportion of metastatic prostate cancer patients. Indeed currently stereotactic body radiotherapy (SBRT) or other local ablative techniques are mature enough to be used in routine clinical practice. Randomized trials have demonstrated that radiotherapy to the prostate could improve overall survival in low burden metastatic prostate cancer patients. However the evidence supporting the use of ablative therapies of the metastases is scarce and of much lower quality. Besides the use of advanced imaging such as PSMA PET/CT has resulted in an important stage migration, which will complicate the analysis of the published data. The goal of this talk is to present the available evidence in favor of metastasis directed therapy for hormone sensitive as well as castration resistant prostate cancer, discuss the reliability of the results, and present major ongoing studies that address the question. SP-0142 Radiation therapy for castrate resistant oligometastatic patients T. Hölscher 1 1 University Hospital Carl Gustav Carus- Technische Universität Dresden, Department of Radiotherapy and Radiation Oncology, Dresden, Germany Abstract text The role of radiation therapy in castration resistant prostate cancer (CRPCa) has been changing in the last years from symptomatic radiotherapy (RTx) in patients with spinal cord compression, fractures or pain, to a more prominent role in treatment. Radionuclide therapy with radium-223 has been shown to prolong survival in selected patients and PSMA ligand therapy is under investigation. Modern PSMA-based, hybrid imaging might identify patients with a limited number of (progressing) metastases (oligometastases), who even could benefit from local ablative RTx measures, i.e. in terms of postponing start of palliative chemotherapy. First clinical data is available. However, high quality comparative clinical trials, including development of blood-based predictive markers, are warranted to define the role of local ablative radiotherapy in selected patients, whose cancer is no longer responding to androgen deprivation.

that there is not agreement among the panellists on the number of metastases to define oligometastic state or even on the existence of oligometatic PC. The majority of big PC studies are based on the conventional imaging (bone scan and total body CT scan), and do not take into consideration modern imaging modalities like multiparametric magnetic resonance (mpMRI), whole body MRI, choline-PET or PSMA PET. Actually, chemotherapy- based studies (CHAARTED) introduced a new definition of low volume metastatic PC and high volume PC (4 or more bone metastases with one or more outside the vertebral bodies or pelvis, or visceral metastases, or both. Please note no impact of pelvic lymph nodes). These features are highly involved in the prognosis of metastatic and oligometastatic PC. In the recent years extensive research has been undertaken in order to define better the biological feature of oligometastic PC. New prognostic markers like microRNA have been investigated in order to better define the patients that may benefit form metastases-directed therapies. SP-0140 Standard of care for systemic treatment - hormone sensitive and CRPC N. James 1 1 The Institute of Cancer Reaearch, Prostate and Bladder Research, London, United Kingdom Abstract text The care of men with newly diagnosed metastatic prostate cancer has undergone considerable change in the last 5 years with increasing evidence for the efficacy of a range of different therapies including docetaxel, a range of androgen receptor targeting therapies (abiraterone, enzalutamide, apalutamide) plus prostate radiotherapy in low volume metastatic disease. The trials underpinning these various therapies mostly ran in parallel and hence we have only limited information of the pros and cons of the growing number of possible treatment permutations – should we simply pick one of the treatments that improve survival when used upfront or can and should we combine therapies? Things we know with reasonable certainty: Androgen deprivation therapy remains a fixed part of therapy Using at least 4 drugs upfront improve survival Docetaxel Abiraterone Enzalutamide, apalutamide Using AR targeted therapy upfront gives a longer time to progression compared to chemotherapy but a shorter duration of CRPC Radiotherapy improves survival in low volume disease Things we need further research to clarify: Whether ADT + 1 therapy is better than ADT + 2 therapies in mHSPC Whether any biomarker can help us with drug selection Whether PSMA PET detected metastases invisible on CT and bone scan matter Whether de novo mHSPC behaves the same as mHSPC with prior therapy Once we move into castrate refractory disease we have further issues: At least 7 drugs work in relapsed disease Abiraterone Enzalutamide, apalutamide, darolutamide Docetaxel, cabazitaxel Radium-223 Olaparib in men with DNA damage repair mutations We do not know the best order for therapies apart from a few exceptions: Cabazitaxel is a better third line therapy post AR targeting and chemotherapy than AR therapy switching Radium should not be used in combination with AR targeted therapy Radium should probably not be used too early in the care

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