ESTRO 36 Abstract Book

S302 ESTRO 36 _______________________________________________________________________________________________

facilitate treatment decision making in the elderly since patient preferences and capacities can be collected more precisely and interpreted in the light of a geriatric view. 5,6 1. Auperin A, Le Pechoux C, Rolland E, et al. Meta-analysis of concomitant versus sequential radiochemotherapy in locally advanced non-small-cell lung cancer. J Clin Oncol 2010;28:2181-90. 2. Driessen EJ, Bootsma GP, Hendriks L, et al. Stage III Non-Small Cell Lung Cancer in the elderly: Patient characteristics predictive for tolerance and survival of chemoradiation in daily clinical practice. Radiother Oncol. 2016 Oct;121(1):26-31 3. Hurria A, Togawa K, Mohile SG, et al. Predicting chemotherapy toxicity in older adults with cancer: a prospective multicenter study. J Clin Oncol 2011;29:3457- 65. 4. Repetto L, Fratino L, Audisio RA, et al. Comprehensive geriatric assessment adds information to Eastern Cooperative Oncology Group performance status in elderly cancer patients: an Italian Group for Geriatric Oncology Study. J Clin Oncol 2002;20:494-502. 5. Blanco R, Maestu I, de la Torre MG, Cassinello A, Nuñez I. A review of the management of elderly patients with non-small-cell lung cancer. Ann Oncol 2015;26:451-63. 6. Gosney MA. Clinical assessment of elderly people with cancer. Lancet Oncol 2005;6:790-797. The evidence that most breast cancer local recurrences develop in close proximity to tumour bed paved the way to the introduction of APBI, an approach in which only the lumpectomy bed plus a 1-2 cm margin is treated, rather than the whole breast. Because of the small volume of irradiation, a higher dose can be delivered in a shorter period of time. Various approaches have been proposed for APBI: multi-catheter interstitial or balloon catheter brachytherapy (BT), intraoperative radiation therapy (IORT) and external beam irradiation (EBI). These techniques are intrinsically different in terms of both radiation delivery and obtainable dose distributions thus leading to different target coverage, dose conformality, and OARs sparing. A number of papers aims at exploring the differences between APBI planning with different techniques. Starting from these comparison studies, we'll go through the main differences between the treatment modalities, trying to identify subgroups of patients who would benefit from a specific approach and to see whether different results are due no only to the technique that was used but also the way it was implemented (e.g. use of non- coplanar beams, partial arcs, blocked regions). In BT no margin is applied around the CTV, which allows reducing the breast normal tissue irradiated with high doses, which seems to correlate with some adverse cosmetic effects. Moreover BT can provide highly conformal dose distribution and steep dose gradients, which allow optimal sparing of critical structures. Nevertheless, due to the shape of the dose distribution, the OARs sparing is strongly dependent on the location of the PTV. IORT could minimize some potential side effects since skin and the subcutaneous tissue can be displaced during radiation delivery. The dose distribution is characterized by a sharp dose fall-off but possibilities to shape the dose distribution are very limited. EBI is attractive since no specific manual Symposium with Proffered Papers: Selection of patients and radiotherapy technique for APBI in the light of new phase III trial data SP-0565 Target coverage and dose to organs at risk using different techniques of APBI (EBI, IORT, BT) L. Marrazzo 1 1 Azienda Ospedaliera Universitaria Careggi, Medical Radiation Physics, Firenze, Italy

skills are required. Several strategies have been used: 3D conformal radiotherapy (3D-CRT), static field intensity modulated radiation therapy (IMRT), volume modulated arc therapy (VMAT), helical Tomotherapy and proton therapy. At the current state, the chosen approach mostly depends on the technical availability. A general result is that intensity modulation techniques are characterized by a better dose conformity when compared to 3DCRT. Non- coplanar beams may be used to reduce the proportion of ipsilateral breast receiving high doses. Proton beams generally show the best performances, allowing the smallest volume of ipsilateral breast to be exposed to low dose, even though scattered beam techniques may be associated to higher skin doses. Not only the planning technique, but also the delivery could affect the dose to OARs: - image guidance could allow for margin reduction thus further reducing dose to uninvolved breast; - left sided lesion could benefit from using a deep inspiration breath-hold technique, which reduces heart dose; - real-time tracking could allow further margin reduction. Currently, we are far from being able to understand whether the dosimetric differences between the different treatment techniques are clinically relevant. SP-0566 External beam partial breast irradiation: changing patient selection based on current evidence I. Meattini 1 1 Azienda Ospedaliero Universitaria Careggi - University of Florence, Radiation Oncology Unit - Oncology Department, Florence, Italy Accelerated partial breast irradiation (APBI) has been introduced as an alternative treatment method for patients with early stage breast cancer (BC). APBI advantages includes shorter treatment time, decreased volume in the breast tissue treated, and cost reduction compared with the standard whole breast irradiation (WBI). The concept of APBI was introduced basing on the results of several large prospective randomized trials comparing postoperative WBI and exclusive surgery, that evidenced the majority of recurrences for patients who did not receive radiation at or in the region of the surgical cavity. The first 5-year results of the IMPORT-LOW trial were presented at the European Breast Cancer Conference (EBCC) 2016 and showed non-inferiority of PBI when compared to WBI in women with low risk early BC, with a 5-year local recurrence (LR) rate of 0.5%. The role of APBI has been investigated in large-scale prospective phase 3 clinical trials using different techniques. Main published results showed conflicting results in terms of local control of disease, while demonstrated equivalent impact in terms of survival when compared with WBI. The Cochrane Database Systematic Review on PBI for early BC published in 2016 showed an increased LR rate with PBI/APBI (small difference), but no evidence of detriment to other oncological outcomes (overall survival, distant metastases). Published data evidenced the crucial role of patient’s selection in clinical outcome. Two trials have reported results of intra-operative radiotherapy (IORT) compared to WBI: the TARGIT-A trial, and the ELIOT trial. In both cases a significant higher rate of LR was observed using APBI, mainly due to high-risk BC patient’s selection for treatment. Conversely, the GEC-ESTRO and the Florence trials, enrolling low risk early BC, obtained an equivalent local control. To note, patient’s population of the Florence trial had a high proportion of luminal-A patients (79% in the APBI, and 73% in the WBI arm) compared to the ELIOT trial (40% and 37% in the IORT and WBI arm, respectively). In the ELIOT trial, the 5-year risk of LR was substantially higher in selected subgroups of patients including those with grade 3 tumors (15.6%), ER- negative disease (14.4%), and triple-negative BC (18.1%). The Florence trial, using a 30 Gy in 5 fractions with IMRT