Long-Term Outcome of Patients with Marginal Zone Non-Hodgkin Lymphoma (MZL) Treated with Yttrium-90 Ibritumomab Tiuxetan: The Mayo Clinic Experience
Authors: Alhaj Moustafa Muhamad , Parrondo Ricardo , Wiseman Gregory , Peterson Jennifer , Witzig Thomas E. , Tun Han W. 
Published: November 2019

Background
MZL is a low-grade non-Hodgkin's lymphoma (NHL) which involves lymph nodes, extranodal sites, or spleen. It is sensitive to radiation therapy, which is used in localized disease with curative intent. Yttrium-90 ibritumomab tiuxetan [(90)Y-IT; Zevalin] is a radio-immunoconjugate (RIC) that targets CD20. It is approved for relapsed/refractory low grade and follicular NHL. The data on its use in MZL is limited. We present long-term outcome of the largest reported cohort of MZL patients who received (90)Y-IT.
Methods
Medical records of patients who received treatment with (90)Y-IT at Mayo Clinic Cancer Center between January 2004 and December 2018 were analyzed. We selected patients with MZL and reviewed clinical data including age, gender, MZL type, clinical stage (Ann Arbor Staging System), treatment response, (90)Y-IT related adverse effects (AEs), as well as lymphoma and treatment related events. All patients received (90)Y-IT according to the standard treatment guidelines. Overall response rate (ORR) and complete response rate (CR) were calculated. Progression-free survival (PFS), time to next therapy (TTNT), and overall survival (OS) were analyzed using the Kaplan-Meier method.
Results
Twenty-one patients were identified (Table 1). The median age at diagnosis was 60 years (range, 11-81) and 71% (15/21) were female. 52% (11/21) were previously-untreated (UMZL) while 48% (10/21) were relapsed (RMZL). The median number of pretreatments in RMZL patients was 2 (range, 1-3). ECOG performance status at the time of treatment was 0 in 90% (19/21) and 1 in 10% (2/21). 62% (13/21) were stage III/IV disease at the time of (90)Y-IT therapy.
The median follow-up was 8.5 years (95% CI; 4.5, 12.4); 17 (81%) patients remain alive. The ORR was 91% (19/21) with the two non-responders being in the RMZL group. The CR rate was 81% (17/21) and 65% (11/17) remain in CR at a median follow-up of 5.7 years (95% CI; 1.4, 11). Nine (43%) patients had a relapse during the study period. More relapses occurred in the RMZL group (7/10; 70%) compared to (2/11; 18%) in the UMZL group. Median PFS (whole cohort) was 10 years (95% CI; 2.1, NR) and TTNT (whole cohort) was not reached (NR) (95% CI; 2.1 years, NR). Median PFS was significantly higher in UMZL group compared to RMZL group NR (95% CI; 2.5 years, NR) vs 2.1 years (95% CI; 0.17, 9.9), respectively (Figure 1-A).Median OS (whole cohort) was 19.3 years (95% CI; 8.9, 19.3) without statistical difference in between UMZL group and RMZL group NR (95% CI; NR, NR) vs 16.6 years (95% CI; 9, 19.4), respectively (Figure 1-B). None of the 11 UMZL patients died at median follow up of 4.7 years (95% CI; 1.6, 9.2). All 4 deaths were in the RMZL group with 3 dying of transformation to high-grade lymphoma at 8, 22, and 25 months post-(90)Y-IT treatment. One patient died of myelodysplastic syndrome 7.3 years post-(90)Y-IT treatment while in CR.
Toxicities were primarily hematologic. Grade ³3 neutropenia was observed in 6/21 (29%) patients with median time to nadir of 48.5 days (range, 19-70) and median time to recovery to normal absolute neutrophil count of 39.5 days (range, 7-476). Grade ³3 thrombocytopenia was observed in 3 (14%) patients with median time to nadir of 35 days (range, 19-357) and median time to recovery of 21 days (range, 2-538). Grade ³3 anemia was observed in only one patient. Only two patients required transfusions and growth factor support. Non-hematologic AEs included mild to severe fatigue in 4 patients.
Conclusion
RIC with (90)Y-IT is efficacious and well-tolerated in patients with previously untreated as well as relapsed MZL. As expected it appears to be more efficacious in previously untreated patients. Long-term complete remission (&gt;5 years) was observed in 52% of the study population (43% of UMZL and 9% of RMZL). Combination of efficacy, tolerability, and treatment schedule most convenient for patients makes (90)Y-IT a reasonable alternative to systemic therapy with immunotherapy, chemotherapy, or chemo-immunotherapy in management of MZL.
Figure 1: (A) Progression-free survival; comparing time to progression or death after (90)Y-IT treatment between previously untreated patients (UMZL) and patients with relapsed MZL (RMZL), (B) Overall survival; comparing time to death from all causes after (90)Y-IT treatment between UMZL patients and RMZL patients.

Disclosures
Tun: Curis: Research Funding; TG Therapeutics: Research Funding; BMS: Research Funding; DTRM Biopharma: Research Funding; Celgene: Research Funding; Mundi-pharma: Research Funding.

OffLabel Disclosure:
The use of Yttrium-90 ibritumomab tiuxetan as a first line treatment for marginal zone lymphoma