ESTRO 38 Abstract book

S457 ESTRO 38

Neurosurgery 2017;0:1-13 ) looking at the cohort of patients treated at our institution as to determine if the SGSCC is reproducible in a larger cohort and ultimately to ensure more risk adapted local treatments for these challenging tumors. Material and Methods Searching our database, we identified patients (n = 142) treated for SBC between 2004 and 2016 with surgery and pencil beam scanning proton therapy. We analyzed the patient specific data focusing on the 5 criteria proposed for the SGSCC (recurrence after prior treatment, tumor size, number of anatomic regions and vessels involved as well as intradural invasion) and sorted them according to their scores (ranging from 2 to 25 points) into three prognostic groups (0-7 points low-risk, 8-12 points intermediate-risk and 13-25 points high-risk). The three groups were then analyzed in regards of local control (LC), local recurrence free survival (LRFS) and overall survival (OS). Results The mean clinical follow up was 53.7 (range, 3.2-152.3) months; of the entire cohort, 34 (23.9%) patients had a local recurrence (LR), resulting in a LC of 75% at 5 years. OS was 83% at 5 years, 12 (8.5%) patients died due to local progression. The LRFS at 5 years was 70%. When split into the three SGSCC prognostic groups, the observed LC was 90%, 72% and 64% ( p = 0.07 ) in the low-, intermediate- and high-risk group, respectively. A similar correlation existed for LRFS with 93%, 89% and 66% ( p = 0.05 ) and for OS with 89%, 83% and 76% (p = 0.65) for the same SGSCC prognostic groups. Conclusion After splitting our patient cohort into three SGSCC risk groups we found a trend towards better outcome for those SBC patients treated with proton therapy with lower as opposed to higher scores. PO-0868 Total Marrow Irradiation in Myeloma Multiple patients candidate to allogeneic transplant A. Chiara 1 , S. Broggi 2 , M. Pasetti 1 , I. Dell'oca 1 , M. Azizi 1 , G. Salvadori 1 , S. Selli 1 , M. Marcatti 3 , A. Assanelli 3 , J. Peccatori 3 , M. Cattaneo 2 , F. Ciceri 3 , N. Di muzio 1 1 Ospedale San Raffaele, Radioterapia, Milano, Italy ; 2 Ospedale San Raffaele, Fisica Sanitaria, Milano, Italy ; 3 Ospedale San Raffaele, Ematologia, Milano, Italy Purpose or Objective Total Body Irradiation (TBI) is as part of the conditioning regimen for haematopoietic stem cell transplantation in haematological diseases. Higher doses of radiation reduce the relapse rate but increase Treatment Related Mortality (TRM). Total Marrow Irradiation (TMI) using Helical Tomotherapy (HT) showed to enhance the therapeutic ratio ( Target dose/Organ At Risk dose) reducing TRM. We report the first results of feasibility, safety and toxicity of myeloablative Treosulfan-based conditioning chemotherapy (cTreoCT) combined with dose-escalating TMI in patients (pts) affected by advanced Multiple Myeloma (MM). Material and Methods Twelve patients (pts) (5 males and 7 females with a median age 59 yrs), affected by advanced MM, were treated from December 2012 to January 2018. All pts received a cTreoCT combined with TMI using HT. 2 Gy (2 times a day) was delivered with a dose escalation approach from 8 to 14 Gy; the total dose is increased in a triplet approach only if extra-hematological (G≥ 4 grade) toxicities don’t appear in the previous dose patient’s group. The treatment was delivered with two different plans: an upper plan from head to half leg (Head First Supine Setup) and with a low plan included the complete legs (Feet First Supine Treatment). Both plans were delivered in helical mode. For each pt a personalized immobilization device, including head, thorax/pelvis and foot masks, was builded.

Results In the base case analysis, SRS and HFSRT total costs were 5,444.68€ and 7,349.83€, and the quality-adjusted life expectancies were 1.4641 and 1.4763. In the probabilistic sensitivity analysis, SRS and HFSRT were associated with a mean total cost of 5,258.77€ and 7,138.91€, and a quality-adjusted life expectancy of 1.4709 and 1.4928 QALYs, respectively. SRS appeared to be 1,880.14€ cheaper than HFSRT with a decrease of quality-adjusted life expectancy of 0.0219 QALYs. The acceptability curves reported a probability of cost- effectiveness of nearly 85.1% and 36.5% for SRS for willingness thresholds of 30,000 and 100,000€/QALY respectively, as represented in the acceptability curves reported in Figure 2.

Conclusion This is the first medico-economic evaluation of SRS and HFSRT in melanoma brain metastases and its results suggest that HFSRT is cost-effective over SRS.

Poster: Clinical track: Sarcoma

PO-0867 Prognostic impact of the “Sekhar Grading System for Cranial Chordomas” - an attempt at validation A. Hottinger 1,2 , B. Bojaxhiu 1 , M. Walser 1 , B. Bachtiary 1 , A. Pica 1 , D.C. Weber 1 1 Paul Scherrer Institute, Center for Proton Therapy, Villigen, Switzerland ; 2 University Hospital Basel, Radiotherapy and Radiation Oncology, Basel, Switzerland Purpose or Objective Skull base chordomas (SBCs) are rare and heterogeneously behaving tumors. Though still classified as benign they can grow rapidly and are locally aggressive. To adapt the treatment to the specific needs of patients at higher risk of recurrence, a preoperative grading system would be useful. The aim of this retrospective analysis was to assess the prognostic impact of the “Sekhar Grading System for Cranial Chordomas” (SGSCC; Brito da Silva et al. Cranial Chordoma: A New Preoperative Grading System.