ESTRO 2020 Abstract Book

S486 ESTRO 2020

PO-0909 High-dose carbon-ion based radiotherapy of primary and recurrent sacrococcygeal chordomas T. Bostel 1,2 , M. Mattke 3 , N.H. Nicolay 2,4 , T. Welzel 3 , D. Wollschläger 5 , S. Akbaba 3 , T. Sprave 4 , J. Debus 2,3 , M. Uhl 3 1 University Medical Center Mainz, Radiation Oncology, Mainz, Germany ; 2 German Cancer Research Center DKFZ, Clinical Cooperation Unit Radiation Oncology, Heidelberg, Germany ; 3 Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany ; 4 Medical Center - University Hospital of Freiburg, Radiation Oncology, Freiburg, Germany ; 5 University Medical Center Mainz, Institute of Medical Biostatistics- Epidemiology and Informatics IMBEI, Mainz, Germany Purpose or Objective This retrospective study aimed to analyze the oncological long-term results and late toxicity of sacral chordoma patients after high-dose carbon-ion based radiation treatment and to identify prognostic factors for local control (LC) and overall survival (OS). Material and Methods A total of 68 patients with a median age of 61 years (range 34 – 84 years) were treated at the at the Heidelberg ion therapy facility. Primary treatment was performed in 52 patients (77%), while 16 patients (23%) received radiotherapy (RT) in the recurrent situation by using carbon-ions either as single-modality treatment or in combination with photons with a median radiation dose of 66 Gy RBE (range 60 – 74 Gy). In 40 patients (59%), RT was performed after tumor resection. The follow-up comprised regular pelvic MRI scans performed at 3-monthly intervals in the first year and at 6-monthly intervals for the following years. Local progress was defined as an increase of the maximum tumor diameter by 10 % or new tumor growth within the target volume. LC and OS were determined using the Kaplan-Meier method. The relevance of several prognostic factors for LC and OS were tested. Results The median follow-up was 60 months (range 1 – 96 months). The lost to follow-up rate was 15% after 5 years. The 5-year LC, metastasis-free-survival, disease-free survival and OS were 43%, 82%, 44% and 82%, respectively. Local recurrence was observed in 31 patients (46%), occurring after a median follow-up time of 24 months (range 2 – 72 months). Only 10% of local relapses occurred later than 5 years after RT. In the multivariate testing, borderline significance was evident when comparing primary and recurrent tumors (5-year LC rates 53% vs. 9%), while the tumor volume and applied radiation dose were unrelated to LC. There was no significant prognostic factor for OS in the multivariate analysis. The incidence of late toxicities ≥ grade 3 was 21% (14 patients). Sacral insufficiency fractures (SIFs) were by far the most common late side effect in our analysis accounting for 49 % of the patients (33 patients). Radiogenic damage to the peripheral nerves, intestinal tract and skin was much less frequently observed with incidence rates of 9% (6 patients), 3% (2 patients) and 9% (6 patients), respectively. Conclusion Our analysis showed moderate long-term local control rates after carbon-ion based RT, whereby sacral chordomas have a particularly poor prognosis in the recurrent situation. Future studies should take further dose escalation into account to optimize therapy outcomes. However, possible benefits of dose escalation must be weighed against the risks of therapy. In our study every fifth patient had grade 3 toxicities and every second patient a SIF.

Poster: Clinical track: Haematology

PO-0910 Efficacy and toxicity of infradiaphragmal radiotherapy fields in lymphoma patients L. Galunic Bilic 1 , F. Santek 1 , M. Soce 1 , J.J. Grah 2 , S. Basic Kinda 3 , I. Radman 3 , Z. Mitrović 4 , M. Martinović 5 , I. Aurer 3 1 University Hospital Center Zagreb, Department of oncology and radiotherapy, Zagreb, Croatia ; 2 Univ. Klinik für Strahlentherapie-Radioonkologie- LKH Graz, Department for radiotherapy, Graz, Austria ; 3 University Hospital Center Zagreb, Department of hematology, Zagreb, Croatia ; 4 University Hospital Dubrava, Department of hematology, Zagreb, Croatia ; 5 University Hospital Merkur, Department of hematology, Zagreb, Croatia Purpose or Objective Most studies of radiotherapy in lymphoma were performed in supradiaphrgamatic localizations. Data on efficacy and toxicity of irradiation of infradiaphragmatic fields are scarce. We therefore performed this retrospective study to analyze our experience with lymphoma patients receiving radiotherapy exclusively to infradiaphragmatic fields. Material and Methods We identified 112 patients treated with external beam radiotherapy between January 2003 and December 2014. The median follow-up for all patients is 51 months (range 1-185 months). There were 69 patients irradiated with 2D technique and 43 using 3D conformal radiotherapy (3DCRT). Median dose was 36 Gy, range 4 to 54 Gy. Medium dose per fraction was 2 Gy, range 1.5 to 7 Gy. Data for long-term side effects were available for 80 patients. Results Five and 10-year overall survival (OS) rates were 69% and 58% respectively and 5 and 10-year event-free survival rates (PFS) 59% and 57% for all patients. The in-field and out-of-field recurrence rates were 5% and 21%. Patients with indolent NHL had 5 and 10-year OS rates of 84% and 63% respectively, and 5 and 10-year EFS rates of 54% and 48%. In patients with aggressive NHL 5 and 10-year OS was 75% and 64% respectively and 5 and 10-year EFS 65% and 65%. OS and EFS was significantly better in the group of patients that were irradiated after one line than after two or more lines of chemotherapy (5-years OS 87% vs. 68%, p =0.001 and EFS 72% vs. 28%, p <0.001). Acute toxicity occurred in 43% patients; gastrointestinal in 26% and hematological in 15%. 2D radiotherapy resulted in more hematologic toxicity than 3D conformal (31% vs. 7%, p= 0.007). Nausea occurred in 10% patients in 2D group and in 28% patients in 3D group (p= 0.020). Long-term side effects were noted in 15% of patients; gastrointestinal in 5%, renal in 4% and secondary malignancy in 2%; there was no significant difference between patients irradiated using 2D and 3D technics. Conclusion Radiotherapy is an effective and safe treatment option for patients with infradiaphragmatic lymphoma providing excellent local disease control with minimal late toxicity. The difference in toxicity between older and newer radiation technics seems less pronounced than for supradiaphragmatic fields. Infradiaphragmatic lymphoma localization should not be regarded as a contraindication for use of radiotherapy. PO-0911 Volumetric total lymphoid hypofractionated irradiation and stem cell transplantation in lymphomas. S. Vagge 1 , F. Guolo 2 , F. Ballerini 2 , S. Agostinelli 3 , D. Tramontano 4 , I. Chiola 4 , E. Olivetta 4 , R. Corvò 4 , E. Angelucci 2 , R. Lemoli 5 1 IRCCS Ospedale Policlinico San Martino, Radiation oncology, Genova, Italy ; 2 IRCCS Ospedale Policlinico San Martino, Hematology, Genova, Italy ; 3 IRCCS Ospedale