ESTRO 2020 Abstract Book

S207 ESTRO 2020

Abstract text Ipsilateral breast tumor recurrence (IBRT) represents a challenge for clinicians where the balance between quality of life and local control has to be weighed against the side effects of re-irradiation therapy. Moreover, the management is not standardized and require not only multidisciplinary tumour board decision with individualized oncologic treatment options but also the consideration of patients' needs, expectations and priorities. The final outcome of breast re-irradiation is difficult to assess because of the wide range of variable treatments that a patient may have undergone. Treatment options for breast tumor recurrence involve surgery, chemotherapy and irradiation with or without hyperthermia. Even though mastectomy is regarded as the standard of care for patients with IBTR, in a selected group of patients second breast conserving therapy is an attractive alternative to mastectomy. There are studies which challenged this approach, and strategies for a second BCT after IBTR are being investigated for selected patients. Re-irradiation for breast cancer is mostly applied as partial breast irradiation and can be delivered either as conformal external beam irradiation (with photons or electrons), interstitial brachytherapy or as intraoperative radiation therapy (IORT). This approach yields high breast preservation rates, does not seem to compromise oncologic safety and is associated with an acceptable incidence of side effects, such as fibrosis, pain, rib fracture, infection, lymphedema, but less acceptable results with regard to cosmesis. Heterogeneity of early and late toxicity reporting together with a variability of applied schedules composed of variable radiotherapy total and fraction doses, hyperthermia schemas, surgical and systemic treatment does not allow to create a clear consensus on the optimal treatment schedule for recurrent breast cancer to achieve best long-term local control and survival with less toxicity. Nevertheless, available results present re-irradiation as an effective and safe modality for the management of recurrent breast cancer. Therefore, the aim of this talk is to present the mentioned points and review the current status of the treatment for recurrent breast cancer. SP-0385 Do we really know what is the best radiotherapy schedule for locally advanced breast cancer? I. Meattini 1 Abstract text Locally advanced breast cancer (LABC) patients are generally classified as stage III disease at presentation with large primary breast cancers and positive regional nodes; cases with skin and/or chest wall involvement, breast edema, or a combination, clinical inflammatory breast cancer (IBC), or advanced clinical regional nodal disease. Some guidelines have included also stage IIB. Optimal treatments for patients presenting with LABC have changed over time and now include multimodality therapy using systemic/target therapy, surgery, and radiation therapy. Sequence of treatments depends on multiple factors, including the extent of disease at diagnosis. Primary systemic therapy (PST) use is increasing, mostly in case of patients affected by triple-negative, HER2- positive, clinically node-positive disease, and in case of inoperable disease. The old-fashioned rationale for use of PST to allow unresectable disease operable has been 1 University of Florence - Azienda Ospedaliero Universitaria Careggi, Radiation Oncology Unit - Oncology Department, Florence, Italy

overcame, integrating tumor biology. Surgical approaches for LABC is also fast evolving: in the majority of case modified mastectomy is used, although some selected cases if non-inflammatory breast cancer are nowadays considered for a breast conserving-surgery strategy. The role of axillary staging, mostly after PST, is also under investigation. Response to PST assessment might allow potential tailoring of therapies, and it has been integrated into current clinical trials design. Postmastectomy radiation therapy (PMRT) trials showed significantly improved locoregional and – in selected high- risk cases - overall survival rates. However, there is a lack of studies specifically evaluating LABC cases, including IBC. Locoregional radiation targets volumes (chest wall/breast and regional nodes) and fractionation (conventional/hypofractionation) is currently under investigation. A multidisciplinary management is crucial to warrant the optimal outcome for these patients. Future perspectives include a tailored approach based on patient-individual risk for disease control failure and tumor biology. Improved outcomes call for high-level multidisciplinary cooperation. SP-0386 The biology of radiation induced secondary malignancy C. Von Neubeck 1 1 Essen University Hospital, Clinic for Particle Therapy, Essen, Germany Abstract text An increasing patient number receives radiation as part of their cancer treatment. The therapy outcome improved for many cancer entities due to developments in e.g. diagnostics, imaging modalities, and radiation techniques. Patient stratification and personalized treatment based on molecular and genetic biomarkers further increased patient’s survival. However, radiotherapy has been shown to be associated with a statistically significant enhanced risk for secondary malignancies, in particular for long-term cancer survivors. The long latency period of ten and more years between radiotherapy treatment and the development of the secondary tumor impedes the evaluation of new techniques and therapies in large prospective clinical trials. Currently, there is a great uncertainty concerning the dose-response relationship and a limited understanding of the complex biological processes involved in radiation-associated carcinogenesis. However, for some factors such as incomplete DNA damage repair, genomic instability, genetic risk factors, patient age at treatment, specific organ/tissue responses, and dose-volume distributions, there is strong evidence for affecting secondary cancer risks. This talk aims to summarize current literature on risks for secondary malignancies from a biological perspective. SP-0387 Radiotherapy and second malignancy: the facts F. De Vathaire (France) Institut Gustave Roussy, Villejuif, France Symposium: Second malignancy after modern radiotherapy: more or less than historical precedents

Abstract not received

SP-0388 Will SBRT, IMRT and protons alter the risks of second malignancy?