S724 3rd ESTRO Forum 2015 from first day of chemotherapy to death of any cause) were evaluated. Results: A total of 43 patients were included. The median follow-up was 45 months (range 6-105 months). Five year DFS, PFS and OS were 90%, 76% and 86% respectively. On post-chemotherapy PET, CR was seen in 35 patients (81%), partial response in three patients (7%) and progression in five patients (12%). Of the patients with CR, three patients (9%) relapsed, all in initial sites of disease with one patient also relapsing in new sites. Three of four patients with bulky disease (defined as a single nodal mass of 10cm or greater) received consolidative RT and none of these patients relapsed. Five year OS for patients with PET CR was 94%. Two patients died, one from progressive disease and one from bleomycin-related lung toxicity. Conclusions: Advanced stage HL with PET CR following ABVD chemotherapy is associated with an excellent prognosis. Relapses were low and occurred in both initial and new sites. The use of consolidative RT for bulky disease provided good disease control, with no relapses observed. EP-1342 Risk of local failure with Cyberknife radiosurgery to the resection bed for large intracranial metastases J. Vogel 1 , A. Hollander 1 , E. Ojerholm 1 , C. Briola 2 , R. Mooij 2 , M. Bieda 2 , J.D. Kolker 2 , S. Nagda 2 , G.A. Geiger 2 , J.F. Dorsey 1 , R.A. Lustig 1 , D.M. O'Rourke 3 , S. Brem 3 , J.Y.K. Lee 3 , M. Alonso- Basanta 1 1 University of Pennsylvania, Department of Radiation Oncology, Philadelphia PA, USA 2 Pennsylvania Hospital, Department of Radiation Oncology, Philadelphia PA, USA 3 University of Pennsylvania, Department of Neurosurgery, Philadelphia PA, USA Purpose/Objective: Stereotactic radiosurgery (SRS) is an alternative to post-operative whole brain radiation therapy (WBRT) following resection of brain metastases. At our institution, CyberKnife (CK) is generally used for local treatment of larger cavities. In this study, we aimed to evaluate patterns of failure with this approach and assess whether size of lesion correlated with local failure. Materials and Methods: We retrospectively reviewed 30 patients treated with CK to 33 lesions between 2011-2014. Both the cavity resection volume (GTV) and CK treatment volume (PTV) were analyzed on treatment planning MRI for all cases. Patterns of intracranial control were analyzed in 26 patients with post-treatment imaging. Survival was estimated by the Kaplan Meier method and prognostic factors for local and distant control were examined with Fisher’s exact test. Results: The most common histologies were lung (42%), breast (21%), and melanoma (15%). The cohort was evenly split by gender and generally RPA I (33%) and RPA II (57%). Median preoperative diameter was 3.3cm and 57% of patients underwent gross total resection. Median cavity volume was 17.5cm 3 (range 2.4-69.8 cm 3 ) and median treatment volume was 25.11cm 3 (range 4.7-90.9cm 3 ). Treatments were delivered to a median 30 Gy in 5 fractions to the 75% isodose line. Synchronous metastases were treated at the time of CK in 33% of cases. The median clinical follow up for the 13 living patients was 16.9 months (range 4.4-35.2) and for the entire cohort of 30 patients was 9.5 months (range 1.0-34.3). Local failure developed in 7 treated cavities (23%) and median time to local failure was not reached. Patients with lung primaries were found to fail locally in five of twelve cases (42%) compared to two of 17 (12%) non lung histologies (p=0.092). Evaluation of both cavity volume and CK treatment volume at a variety of cut-off points showed no association with local failure and size (p>0.61 and 0.64, respectively). Distant brain failure occurred in 20 cases (63%) at a median of 4.6 months. Distant failure developed in eight of nine patients with synchronous metastases (89%) compared to 11 of 20 without synchronous metastases (56%) (p=0.107). Salvage therapies included WBRT (23%) performed at a median of 5.1 months from treatment and additional SRS (40%) at a median of 4.9 months from treatment. Leptomeningeal carcinomatosis developed in 12 cases (40%). Patients survived a median of 10.1 months from the time of treatment. Conclusions: This study suggests that large resection cavities are likely to achieve equivalent local control as smaller resection beds using adjuvant CK strategy. However, patients with lung primaries appear more likely to fail within this cohort. Most patients do develop intracranial failure which was correlated with synchronous metastases at the time of CK. The majority of patients with large cavity volumes were spared or delayed WBRT with the use of local CK therapy. EP-1343 Stereotactic radiotherapy (SBRT)in the treatment of lung metastases from bone and soft tissue sarcomas F. Salvi 1 , R. Frakulli 2 , A. Longhi 3 , S. Ferrari 3 , S. Cammelli 2 , D. Balestrini 1 , M. Palombarini 4 , S. Magi 4 , A.G. Morganti 2 , G. Frezza 1 1 Ospedale Bellaria, Radiation, Bologna, Italy 2 Policlinico Universitario S. Orsola-Malpighi, Radiation, Bologna, Italy 3 Istituto Ortopedico Rizzoli, Musculoskeletal Oncology Department, Bologna, Italy 4 Ospedale Bellaria, Medical Physics Unit, Bologna, Italy Purpose/Objective: The most common site of relapse in muscoloskeletal sarcomas is lung. Metastasectomy is considered the standard of care in these patients (pts). In those unfit for surgery SBRT might represent however an alternative approach. The purpose of this study is to evaluate local control and toxicity of SBRT in a group of pts treated for lung metastases (LM) from bone and soft tissue sarcomas. Materials and Methods: From October 2010 to July 2014, 24 pts with LM from sarcomas not amenable to surgery were treated with daily cone beam CT guided SBRT. 22 of them had already been submitted at least once to thoracic surgery procedures, and 16 pts had been treated with several lines of chemotherapy. In 50% of pts the primary tumor was a soft tissue sarcoma and in 50% a bone sarcoma (Ewing sarcoma: 5 pts; osteosarcoma: 3 pts; chondrosarcoma: 4 pts). 21% of pts had LM at diagnosis whereas 79% developed LM at a mean of 39,9 months after initial diagnosis. 71 lesions were treated with SBRT. All patients underwent computed tomography simulation. Active breath control (ABC©) was employed to reduce internal margin in lesions located in the lower lobes. Dose was prescribed to 80% isodose. Administered dose ranged from 30 to 60 Gy in 3-8 fractions. Follow-up (fu) included physical examination and a chest CT scan +/- FDG PET/CT every 3 months after treatment. Response rates were