ESTRO 2021 Abstract Book

S896

ESTRO 2021

(aGVHD) was 30% and of moderate chronic GVHD (cGVHD) 11% Conclusion

Single daily high-dose per fraction TMI as conditioning regimen for second allo-HSCT seems to be a safe and effective treatment. Probably the high therapeutic ratio of TMI is the key to perform also whole marrow re- irradiation after previous TBI regimens.

PO-1077 Population-based study on the association between autoimmune disease and lymphoma in Korea J.S. Kim 1,2 , I.H. Kim 1 , J.M. Byun 3 , J.H. Chang 1,2 1 Seoul National University College of Medicine, Department of Radiation Oncology, Seoul, Korea Republic of; 2 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of; 3 Seoul National University Hospital, Department of Internal Medicine, Seoul, Korea Republic of Purpose or Objective We aimed to evaluate the association between autoimmune disease (AID) and lymphoma incidence in the Korean population. We also aimed to compare the overall survival (OS) in patients with AID-associated lymphoma (AAL) with that in patients with lymphoma without AID. Materials and Methods We used National Sample Cohort 2002-2015 provided by National Health Insurance Service. Among 1,011,638 patients, 994,496 were recruited for the final cohort: 130,987 patients (13.2%) in the AID group and 863,509 (86.8%) in control. Lymphoma was diagnosed in 1,162 patients and 322 patients with accompanying AID, irrespective of the time point of diagnosis, were defined as AAL. Of those, patients who experienced lymphoma development at least one year after AID diagnosis were defined as post-AID lymphoma ( N =155). Results The median follow-up duration was 13.7 years. AAL accounted for 0.03% of total and 27.7% of lymphoma cases. AID patients experienced more Epstein-Barr virus (0.02 vs. 0.01%, P =0.027) or Helicobacter pylori infection (63.9 vs. 41.4%, P <0.001) than the control group did. AID was associated with a 1.45-fold increased risk of lymphoma. The median time interval from AID to AAL was 10.9 months. The risk of lymphoma increased in the order of: psoriasis (adjusted odds ratio [AOR] 1.61), systemic lupus erythematosus (AOR 3.99), multiple sclerosis (AOR 4.52), and sarcoidosis (AOR 26.37). Sjogren syndrome was not related to lymphoma in this cohort. The 5-year OS in AAL was not different from that in lymphoma patients without AID (60.9 vs. 61.5%, P =0.970). Conclusion The association patterns in AAL in Korean population were different from those of Western countries. Further studies on lymphomatogenesis from distinct baseline characteristics (e.g. chronic infection status) would elucidate the difference based on race and ethnicity. PO-1078 HDR brachytherapy for treatment of primary cutaneous lymphoma at complex sites and curved surfaces V. Sim 1 , I. De Francesco 1 , S. Whittaker 2 , F. Child 2 , M. Wain 2 , S. Aldridge 3 , E. Jones 3 , K. Freeman 3 , S. Morris 1 1 Guy's Cancer Centre, Clinical Oncology, London, United Kingdom; 2 Guy's and St Thomas' NHS Foundation Trust, St John's Institute of Dermatology, London, United Kingdom; 3 Guy's Cancer Centre, Radiotherapy, London, United Kingdom Purpose or Objective Radiotherapy is an important treatment for cutaneous lymphomas with high response rates. Some sites of skin involvement are difficult to treat with standard orthovoltage or electron beam radiotherapy. We present a service evaluation of our experience and technique using HDR brachytherapy. Materials and Methods Patients referred for radiotherapy to primary cutaneous lymphomas at difficult complex curves sites were selected for treatment with HDR brachytherapy. Two methods were used; 4 patients were planned using 3D printed mould technique and 15 patients were planned with a Friesburg flap applicator. The patients were CT planned using Oncentra planning system and treated with I-192 on the Flexitron afterloader system. Patient’s response and toxicity outcomes were collected with photographs of the areas treated pre and post treatment. Results 19 patients (18 Mycosis Fungoides, 1 PCMZL (Primary Cutaneous Marginal Zone Lymphoma)) were treated using HDR brachytherapy (BT) from February 2014 – September 2019. The sites treated are hand =5, forearm =5, lower limb =3, foot =3, nose =2, and eyebrow =1. Small fields were treated with 8Gy in 2 fractions (#) or 12Gy/3#, larger fields and re-irradiation were treated with 24Gy/12# or 20Gy/10#. All patients had complete response to BT locally. Toxicities recorded were G2 radiation dermatitis = 1, cellulitis =1, G2 localised pain =2. 11/19 (58%) were re-irradiated using BT. On average these patients had 2 courses of RT previously and only 4/11 (37%) had recurrences within the BT treatment field. 5/19 (26%) patients had a small local recurrence within the treated field that later responded to superficial radiotherapy.