ESTRO 37 Abstract book

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ESTRO 37

especially volumetric modulated arc therapy (VMAT) allow treatments of larger convex fields (eg scalp, forehead, cheeks, forearms, legs) safely. We present our initial cohort of forty fields. Material and Methods Patients with large symptomatic fields of clinical Bowen's disease that had given rise to histologically confirmed cSCC were consented and treated. Radiotherapy metrics were recorded. In vivo dosimetry was performed to ensure that the planned dose was delivered. Acute toxicity, quality of life and oncological outcomes at six months were recorded. Results Thirty patients with 40 areas including 15 scalps, 10 arms, 7 cheeks and 8 legs were treated with median follow up of six months. The average size of the fields treated was 60 cm². Acute toxicity was manageable, quality of life improved, the need for further therapy for invasive disease decreased and there were no long term side effects at this early stage. Conclusion VMAT field therapy is safe and effective at six months. Longer follow up is needed to assess long term oncological outcome and quality of life. EP-1625 Cyberknife Radiosurgery On Brain Metastases From Melanoma In The Era Of Systemic Target Therapy. G. Fanetti 1 , G. Marvaso 1 , D. Alterio 1 , A. Ferrari 1 , D. Sibio 1 , C. Francia 1 , E. Cocorocchio 2 , L. Pala 2 , E. Rondi 3 , S. Vigorito 3 , B. Jereczek-Fossa 1 1 IEO - European Institute of Oncology, Division of Radiation Oncology, Milano, Italy 2 IEO - European Institute of Oncology, Division of Melanoma and Sarcoma Medical Oncology, Milano, Italy 3 IEO - European Institute of Oncology, Unit of Medical Physics, Milano, Italy Purpose or Objective To evaluate neurotoxicity and clinical outcome in patients (pts) treated with Stereotactic Radiotherapy/ Radiosurgery (SRS) delivered by Cyberknife® and concomitant target therapy (i.e. immunotherapy and protein kinase inhibitors) to brain metastases from Melanoma (MBM). Material and Methods Data were collected retrospectively. Inclusion criteria consisted in: 1) histologic proof of melanoma, 2) brain metastases diagnosed with Magnetic Resonance Imaging (MRI), 3) systemic treatment with anti CTLA4, anti-PD1 or BRAF inhibitor ± MEK inhibitor 4) RSR delivered concurrently or within 6 weeks before or after the systemic therapy. Progression Free Survival (PFS), Brain- PFS (b-PFS), Overall Survival (OS) and Local Control (LC) were elaborated with Kaplan-Meier curves and defined as time between the end of SRS and clnical progression at any site, brain progression, death or last follow up and in field progression, respectively. Neurotoxicity was evaluated as headache, nausea/vomiting, seizure and scored with Common Terminology Criteria for Adverse Events (CTCAE) v4.0. Neurotoxicity and radionecrosis were collected every 2 months with clinical examination and MRI. Results Fifty-eight MBM were treated in 26 pts (median age 54 years, range 34-81 years, 15 male). Primary tumor occurred in head and neck district, body, extremities and mucosae in 3, 13, 6 and 4, respectively. BRAF mutation was found in 13 pts. Median time from primary treatment

and SRS was 42.4 months (range: 16.7-220.6). Systemic therapy consisted of anti CTLA4, anti-PD1 and BRAF inhibitor ± MEK inhibitor in 9, 6 and 11 pts, respectively. All pts received premedication with dexamethasone before SRS. Median dose delivered was 21 Gy in single fraction (range: total dose 15-36 Gy in 1-3 fractions). SRS was delivered at the time of first, second, third and fourth line of systemic treatment in 9, 10, 5 and 2 pts, respectively. The median follow up was 8 months (range: 1.5-27.7). At six months PFS, b-PFS, OS and LC were 30, 54, 65 and 60%, respectively. Only 2 out of 23 evaluable pts complained headache G1 after SRS (2 pts died before the first follow up and 1 was followed in another hospital). In 5 pts asymptomatic radionecrosis was found in subsequent MRI: 3 received BRAF inhibitor ± MEK inhibitor and 2 anti-PD1. At the time of analysis 20 pts were dead of disease and 6 were alive with disease. Conclusion The association of SRS with modern systemic target therapies resulted to be safe and no severe toxicities were reported in our cohort of pts. Outcome results of the present serie are in line with literature confirming the poor prognosis of pts with MBM. Further studies are needed to determine the optimal timing of SRS in combination with systemic therapies. EP-1626 Tumour volume influences outcome after surgery and photon RT for chordoma and chondrosarcoma E.R. Gatfield 1 , D.J. Noble 2 , G.C. Barnett 1 , N.Y. Early 3 , A.C.F. Hoole 3 , N.F. Kirkby 4 , S.J. Jefferies 1 , N.G. Burnet 2 1 Addenbrooke's Hospital, Neuro-oncology Unit, Cambridge, United Kingdom 2 University of Cambridge, Department of Oncology, Cambridge, United Kingdom 3 Addenbrooke's Hospital, Department of Medical Physics and Clinical Engineering, Cambridge, United Kingdom 4 University of Manchester, Division of Molecular and Clinical Cancer Sciences, Manchester, United Kingdom Purpose or Objective To evaluate the long term outcomes of patients with chordoma and low-grade chondrosarcoma, of the skull base and spine, following surgery and high-dose X-ray radiotherapy. Material and Methods High-dose photon radiotherapy was delivered to 28 patients at the Neuro-oncology Unit at Addenbrooke’s Hospital (Cambridge, UK) between 1996 and 2016. Twenty-four patients were treated with curative intent, 17 with chordoma, 7 with low-grade chondrosarcoma, with a median dose of 65 Gy (range 65-70 Gy). Eight required metal reconstruction. Local control and survival rates were calculated using the Kaplan-Meier method. Results The median follow up was 83 months (range 7-205 months). The five year disease-specific survival for chordoma patients treated with radical intent was 85%, and the local control rate was 74%. The five year disease- specific survival for chondrosarcoma patients treated with radical intent was 100%, and the local control rate was 83%. The mean planning target volume (PTV) was 274.6 ml (median 124.7 ml). A PTV of 110 ml or less was a good predictor of local control, with 100% sensitivity and 63% specificity. For patients treated with radical Electronic Poster: Clinical track: Sarcoma