Abstract Book

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ESTRO 37

in multiple myeloma). Data of patients treated in our institution were added. Equivalent-dose of radiotherapy was calculated with an alpha/beta ratio of 10. Logistic regression, stratified on study was performed to assess dose-effect relationship and chi-2 test was performed to determine a cut-off in the dose of radiotherapy. Results We obtained individual data of 386 patients with HNPEM from 80 series published since 1965, including 31 patients from our institution. The mean equivalent dose of radiotherapy delivered was 45.8 Gy ± 9.8 Gy. Median follow-up was 5.0 years (inter-quartile range (IQR): 2.5- 9.0). Sixty two patients (16.1%) developed a local recurrence at a median time of 12.5 months after radiotherapy (IQR: 6 to 42 months). Seventy three patients (18.9%) developed a multiple myeloma at a median time of 22.9 months after radiotherapy (IQR: 12 to 41 months). The logistic regression between the equivalent dose of radiotherapy and the local control showed an odds-ratio of 0.96 (IC95%: 0.92-1.00; p = 0.04). Patients who received a dose ≥ 49 Gy, had less local recurrence: 17/158 patients (10.8%) vs. 45/228 patients (19.7%) (Chi-2 = 4.93 and p = 0.03). No dose- effect relationship was found for the evolution in multiple myeloma. Discussion: The recommended dose for treating this pathology with radiotherapy is 40 to 50 Gy. This recommendation is not evidence-based given the rarity of HNPEM. This systematic review of the litterature allows taking into account a significant number of patients for whom individual data of radiotherapy and disease outcome data have been published. It is the first study of this kind for HNPEM. Conclusion Radiotherapy provides good local tumor control in patients with HNPEM. Our data provide the largest retrospective evidence of a dose-response relationship in radiotherapy for HNPEM. According to our results, the dose delivered should be ≥ 49Gy to improve the local tumor control. It would be interesting to initiate a prospective cohort of patients to standardize the management of this rare disease which should integrate evolutions in the molecular characterization. EP-1246 Radiotherapy after autologous stem cell transplant in recurrent or refractory Hodgkin's lymphoma F. Matrone 1 , C. Furlan 1 , M. Rupolo 2 , R. Ciancia 2 , E. Zanet 2 , B. Montante 2 , F. Navarria 1 , E. Palazzari 1 , E. Farina 1 , P. Bulian 3 , M. Mascarin 1 , A. De Paoli 1 , G. Franchin 1 , M. Michieli 2 1 Centro di Riferimento Oncologico, Department of Radiation Oncology, Aviano, Italy 2 Centro di Riferimento Oncologico, Unit of Cell Therapy and High Dose Chemotherapy, Aviano, Italy 3 Centro di Riferimento Oncologico, Clinical and Experimental Onco-Hematology Unit, Aviano, Italy Purpose or Objective To retrospectively assess outcome and toxicity of involved-field radiotherapy (IFRT) after high-dose chemotherapy plus autologous stem cell transplant (HD- ASCT) in patients with recurrent or refractory Hodgkin lymphoma (HL). The secondary aim was to evaluate whether the German Hodgkin Study Group (GHSG) risk model improve prognostication in this setting. Material and Methods We performed a retrospective analysis of 30 consecutive patients diagnosed with recurrent or refractory HL who underwent HCT-ASCT and subsequently received consolidative IFRT at a single institution from 2004 to 2016. Our policy was of adding IFRT in patients with positive PET scan before ASCT (23/30 patients, 77%), and/or irradiating sites of bulky disease at relapse (11/30 patients, 37%). Patients were stratified into 4 risk groups according to the presence of 5 clinical risk factors (RFs)

identified by the GHSG; (1) stage IV disease; (2) time to relapse ≤3 months; (3) ECOG-PS ≥1; (4) bulk ≥5 cm; and (5) inadequate response to salvage chemotherapy. The risk categories were identified based on the sum of these equally weighted RFs. Group-stratified Kaplan-Meier PFS curves were estimated and compared using the log-rank test, starting from the date of completion of IFRT. Results The median interval from ASCT to IFRT was 3 months (range, 1-7 months), and the median IFRT dose was 35 Gy (range, 12–40 Gy). At a median follow-up of 35 months (range, 1-132 months), the 2-year PFS in the entire series was 60%. When examining the 4 different GHSG prognostic groups, the PFS at 2 years for each group was 86%, 83%, 50%, and 36% for patients with score = 0, score = 1, score = 2, and score = 3 to 5, respectively (p=0,01). Only 5 patients failed in the IFRT site, corresponding to a in-field control rate of 83%. Four patients out of the 25 who had medistinal radiation (16%) developed pulmonary events, including 1 case of fatal interstitial penumonitis 1 month after IFRT. Conclusion Adjunctive radiotherapy after ASCT may contribute to improved PFS in selected HL patients, with an acceptable toxicity. In this setting, patients with < 3 RFs had a favourable outcome. EP-1247 Effect of dose-rate on pulmonary toxicity in patients with hematologic malignancies undergoing TBI. D.Y. Kim 1 , H.C. Kang 1 , I.H. Kim 1 , S.S. Yoon 2 , H.J. Kang 3 1 Seoul National University College of Medicine, Radiation oncology, Seoul, Korea Republic of 2 Seoul National University College of Medicine, Internal Medicine, Seoul, Korea Republic of 3 Seoul National University College of Medicine, Pediatrics, Seoul, Korea Republic of Purpose or Objective This study evaluated the effect of radiation dose rate in patients with hematolymphoid malignancies undergoing myeloablative conditioning with total body irradiation (TBI) for hematopoietic stem cell transplantation (HSCT). The incidence of pulmonary toxicity (PT) and treatment efficacy were compared between conventional dose rate (≥ 6 cGy/min) and reduced dose rate (< 6 cGy/min) Material and Methods A total of 77 patients who underwent t TBI-based myeloablative conditioning for hematolymphoid malignancies at Seoul National University hospital between 2000 and 2016 were reviewed. We divided the patients into the conventional (≥ 6 cGy/min, n = 54) and reduced (< 6 cGy/min, n = 23) group according to the dose rate of TBI. Total TBI dose ranged from 9 to 12 Gy and was delivered in 3 to 4 fractions once daily without a day interval. Lung shielding technique was not used. PT was defined if there is one or more of the following three criteria: clinical symptoms, radiographic evidence, and ventilatory defects on pulmonary function tests. We compared the cumulative rate of PT, overall survival, relapse, and transplantation-related mortality (TRM which was defined by 3-month mortality without progression) between the two groups using the Kaplan– Meier method. Furthermore, we performed subgroup analysis by the etiology of PT (infection vs. non- infection). Factors associated with the development of PT were assessed in Cox regression analysis. Results Total average follow-up time was 40.7 months. Median follow-up time were 10.6 months in the reduced group and 12.6 months in the conventional group. Overall, PT occurred in 50 patients and was significantly associated with the groups classified by dose rate. The incidence of PT at 3 months and 6 months were 21.7% and 39.7% in the reduced group, 37.1% and 52.3% in the conventional