590 | REAL WORLD OUTCOMES OF THE FIRST‐LINE TREATMENT OF LOCALIZED EXTRANODAL MARGINAL ZONE LYMPHOMA OF OCULAR ADNEXA OR ORBIT

Introduction: Radiotherapy (RT) is considered as the standard treatment for localized extranodal marginal zone lymphoma of the ocular adnexa or orbit (OAMZL). However, rituximab monotherapy (RM) or rituximab + chemotherapy (R-CHT), as well as only watch and wait policy for patients (pts) with radical surgery (Surg) are sometimes applied. Aim: to analyze the outcomes of Surg, RT, RM and R-CHT in the localized OAMZL. Methods: Pts with Lugano stage I OAMZL prospectively enrolled in the NiHiL registry (NCT03199066) were retrospectively analyzed. Treatment choice was based on institutional policy and physician/patient preference. Fisher's exact test, t-test, and Kaplan-Meier and Cox regression were used for statistical analysis. Results: Between 2005 and 2023, 103 pts with stage I OAMZL were identified. Of these, 16 were treated with Surg only (SurgG), 39 with RT [median dose 30 Gy (4–44); RTG], 20 with RM [median 8 doses (4–8)], 14 with R-CHT (7 R-CVP, 6 R-chlorambucil, 1 R-CHOP). Other heterogeneous approaches were used in 14 pts. Median follow-up was 6.3 years. Given the similar outcomes, the RM and R-CHT groups were evaluated together in further analysis (SystG). In SurgG, median age was 64 years, 44% were male, 33% had elevated LDH, 19% had high MALT-IPI. In RTG versus SystG, age (median 63 vs. 63), male gender 47% versus 50%, elevated LDH 38% versus 35%, tumor bulk > 5 cm 5% versus 3%, high MALT-IPI 8% versus 12% were similar, but ECOG PS ≥ 2 showed a trend for significant difference: 13% versus 0%, p = 0.056. The 5-year progression free survival (PFS) and overall survival (OS) probability for the whole group was 73% and 90% resp. In SurgG, the 5y-PFS, time to next treatment (TTNT) and OS rates were 68%, 74% and 100%. The 5y-PFS of 74% was identical in both RTG and SystG, but a trend for longer TTNT was observed in RTG (5y-TTNT 86% vs. 68%, HR 0.483; p = 0.142) due to a lower need for 2nd line treatment in pts who achieved partial remission or stable disease only. OS was significantly worse in the RTG versus SystG with 5y OS rates of 87% versus 97% (HR 2.553; p = 0.049) and 14 versus 4 deaths. Of these, 3 deaths were due to the lymphoma (all in RTG) and 1 was therapy related (COVID-19 in SystG). There was significant difference in the relapse pattern with 7 systemic out of 8 in RTG versus 6 localized out of 7 in the SystG, p = 0.010. Toxicity data were available for 34 pts diagnosed after 2013. RT was associated with gr. 1–2 conjunctivitis (41%), blepharitis or dermatitis (30%), dry eye syndrome (35%) and 1 case of gr. 3 cataract. In SystG, the main toxicities were hematotoxicity (33% gr. 3–4 solely in R-CHT group) and infections (24%, except for 1 case gr. 2 only). Conclusions: Watch and wait strategy may be considered in patients with radically resected OAMZL. In actively treated pts, while RT, Rtx and R-CHT led to comparable PFS, RT is associated with best local control. RM could be considered in cases where avoiding potential RT-associated toxicity is of primary importance. Keywords: extranodal non-Hodgkin lymphoma; indolent non-Hodgkin lymphoma Potential sources of conflict of interest: J. Ďuraš Consultant or advisory role: Abbvie, Roche, Takeda, Eli Lilly, SOBI, Bristol Myers Squibb Honoraria: Abbvie, Roche, Takeda Educational grants: Roche D. Šálek Consultant or advisory role: Roche Honoraria: Roche, Swiss Biopharma Educational grants: Roche, Gilead A. Sýkorová Consultant or advisory role: Takeda A. Obr Consultant or advisory role: Roche, Eli Lilly, Janssen, Medison Pharma Honoraria: Roche, Eli Lilly, Janssen Educational grants: Roche M. Trněný Consultant or advisory role: Abbvie, Amgen, Autolus, Bristol-Myers-Squibb, Caribo Biosciences, Incyte, Janssen, Gilead, Morphosis, Novartis, Roche, SOBI, Swixx, Takeda Honoraria: Amgen, Bristol-Myers-Squibb, Janssen, Gilead, Morphosis, Novartis, Roche, SOBI, Swixx, Takeda Educational grants: Abbvie, Gilead, Janssen, Roche, Takeda, SOBI