ESTRO 2020 Abstract Book

S491 ESTRO 2020

Endpoints were objective response rate (ORR), response duration, site of relapse and progression-free survival (PFS). Results A total of 49 patients were identified, with a median age of 62 years (29-83). Median follow up was 63 months (2- 201). 43% had underlying SS, of which 91% were female. A total of 61 sites were treated with RT, with the orbit (49%) and parotid (38%) being the most prevalent. LDRT (4Gy/2#) was delivered to 38 (62%) sites, with an IDRT (25.2Gy/14# or 24Gy/12#) being used in 21 (34%.) sites. The remaining 2 sites received 8Gy/4# and 20Gy/5#. 90% of the IDRT was used in patients without SS. ORR (complete and partial response) at 6 weeks post RT for all, LDRT and IDRT was 95%, 92% and 100% respectively with no difference between SS and no-SS patients. Relapse rate was higher in LDRT than IDRT group (36% v 14%). Mean duration of response for all patients, LDRT & IDRT groups was 58, 49, and 74 months respectively. The duration of response in the LDRT group was 62 months in patients with SS and 28 months in those without. Patients with SS who were retreated with LDRT had a mean duration of response of 77 months. Overall, 50% of relapses occurred at the same site. Transformation to a high grade lymphoma occurred in 6% of all patients. The 5 year PFS was 77% and 5 year overall survival was 95%.

Conclusion Both LDRT and IDRT provide high ORR and a durable control for patients with head and neck MALT lymphoma. LDRT patients had a higher rate of relapse with a shorter duration of control but lasting results are achieved following subsequent LDRT, particularly in patients with SS. LDRT is an excellent option for SS patients providing high ORR, shorter course, lower toxicity and chance for effective re-treatment. PO-0920 Low dose radiation therapy (2 Gy x 2) in the treatment of Marginal Zone Lymphomas V. De Luca 1 , S. Bartoncini 2 , G.C. Iorio 1 , R. Parise 1 , E. Orlandi 1 , C. Cavallin 1 , C. Palladino 1 , M. Levis 1 , U. Ricardi 1 1 University of Turin, Department of Oncology- Radiation Oncology, Turin, Italy ; 2 AOU Città della Salute e della Scienza, Department of Oncology- Radiation Oncology, Turin, Italy Purpose or Objective Non Hodgkin Lymphomas (NHL) represent a heterogeneous group of malignant hematological neoplasms, among whom indolent ones account for 40% of all the diagnosis. Radiation therapy (RT) is currently the standard management for patients with stage I and II. Historically, patients with indolent lymphoma have received treatment with conventional doses of 24-30 Gy, with excellent local control (LC) rates. Several studies reported similar high LC rates, with reduced toxicity with lower doses of RT, suggesting that the effective dose for the definitive

Conclusion Early-stage PBL have an excellent prognosis treated with R-CHOP chemotherapy plus an adequate dose of RT.

PO-0919 Low vs intermediate dose radiotherapy in head & neck MALT lymphoma with and without Sjogren syndrome C. Shelley 1 , J. Brady 2 , F. Rahman 2 , G. Mikhaeel 2 1 Guys and St. Thomas's NHS Trust, Oncology, Nr. Reading, United Kingdom ; 2 Guys and St. Thomas's NHS Trust, Oncology, London, United Kingdom Purpose or Objective Extranodal marginal zone lymphomas of mucosa- associated lymphoid tissue (MALT) arise throughout the body. Head and neck is the second commonest site after the stomach and there is a strong link with Sjogren syndrome (SS). Low dose radiotherapy (LDRT) is an attractive option due to high frequency of multifocal disease and need for re-treatment. We compared low- and intermediate-dose (IDRT) in this context. Material and Methods We carried out a retrospective review of patients with head and neck MALT lymphoma treated in our centre from 2003-2018. We collected information on patient demographics, treatment details and outcomes. Inclusion criteria were histologically confirmed MALT diagnosis, treatment with RT and complete clinical records.