ESTRO 2020 Abstract Book

S490 ESTRO 2020

function of age ( p=0.04) . The 5y-OS and 10y-OS were respectively 96% and 91%. Local recurrences developed in 21.4% of pts (9/42). 16 pts progressed to MM (38.1%). The 5y-progression to MM free survival (PMFS) and the 10y- PMFS were respectively 68.6% and 61.9%. Impact of several factors on modulating OS was evaluated. Specifically, age at diagnosis was the only significant prognostic factor of OS (p=0.005), whereas type of treatment, surgery, pain and tumor size were not predictive.

immunodeficiencies. Exclusion criteria were all other nodal and extranodal - including bone marrow - involvement. Bone involvement was defined by percutaneous or surgical bone biopsy. In total, 6 patients were finally included. Subsequently, we analyzed the clinical features, management and prognosis of these cases. Results Table 1 presents clinical and treatment characteristics of patients. The database of our center included 270 patients affected by non-Hodgkin lymphoma who received radiotherapy. Only six (2.22%) patients had a diagnosis of PBL. Median age was 50 years (18-71 years) and a male:female ratio of 5. Spine represents the most frequent sites of involvement, followed by the humerus. The most common symptom was pain (50%). All the patients had a good performance status (≤2) and IE stage disease. Diffuse large B-cell lymphoma (DLBCL) accounts for half of the cases, while the other half are represented by indolent lymphoma. Five patients received a combined modality treatment (chemotherapy plus radiotherapy) and one received radiotherapy alone. All cases achieved a complete remission; however, the case that received only radiotherapy experienced relapse 5 months after finishing treatment. Subsequently, this case performed salvage treatment with chemotherapy (R-CHOP cycles 6), achieving complete remission again. At a median follow- up of 104 months (7.6-135.6 months), 83.3% (n=5) patients were alive without evidence of disease, and 16.7% (n=1) died of a cerebrovascular disease. The average overall survival is 121.3 months (95% CI, 88.6-153.9 months) and progression-free survival is 117.4 (95% CI, 77.2-157.7%).

Conclusion Our data confirm the good results achievable with RT to treat SP. Also from our analysis, there is no statistically significant correlation between higher doses and better disease control. Similarly, no correlation between outcomes and type of SP has emerged. No statistically significant correlations were found that could define which pts have the greatest possibility of evolving into MM. Probably other biological factors can influence the outcome of the SP. PO-0918 Early-stage primary bone lymphoma: a single- center experience. A.A.A. Geng Cahuayme 1 , R. Vergés Capdevila 1 , J. Giralt López de Sagredo 1 , V. Reyes López 1 1 Hospital Universitario Vall d'Hebron, Radiation Oncology, Barcelona, Spain Purpose or Objective Primary bone lymphoma (PBL) is a rare entity. PBL accounts for less than 2% of all malignant lymphomas in adults, between 3 to 7% of primary bone malignancies, and less than 1% of all non-Hodgkin lymphoma. Most studies recommend combined modality therapy, however there is no standard treatment for PBL in limited stage. Randomized studies are not available in the literature to obtain optimal management due to the low incidence of the disease. Upon the need for more data on limited stage PBL in order to manage this illness properly, we retrospectively analysed all the PBL cases in our center. Material and Methods Data from 270 patients with pathological proven non- Hodgkin lymphoma (NHL) who received radiotherapy (RT) from January 2008 to August 2019 at Vall d’Hebron University Hospital were retrospectively analyzed. Patients were included in the study if they had any of the following factors: (1) PBL at diagnosis; (2) age ≥ 18 years; (3) histological diagnosis of lymphoma; (4) stage IE-IIE according to the Lugano classification; (5) complete staging work-up with whole body positron emission tomography/computed tomography (PET/CT) scanner and bone marrow biopsy; and (6) no evidence of