ESTRO 2020 Abstract book

S536 ESTRO 2020

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. 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%.

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 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

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