Comparative outcomes of oncologic therapy in gastric extranodal marginal zone (MALT) lymphoma: Analysis of the Surveillance, Epidemiology and End Results (SEER)-Medicare database.

Abstract

75 Background: Therapy for H. pylori (HPy)-negative or recurrent gastric MALT lymphoma is largely based on single-arm trials. The aim of this observational study was to compare outcomes after surgery, radiation (XRT) or chemotherapy (CT) in the SEER-Medicare dataset. Methods: Gastric MALT lymphoma cases diagnosed between 1997 and 2007 were selected, excluding patients without adequate Medicare coverage at diagnosis or follow up. Outcomes of XRT and CT were compared in stage IE group balanced by a propensity score. Flexible parametric models were used to study overall (OS) and lymphoma-specific survival (LSS). Treatments were evaluated with competing risk models, reporting hazard ratios (HR) and 95% confidence intervals (95%CI). Results: Among 1134 patients (median age: 77 years, median follow-up data: 4.3 years), 50% had no recorded oncologic treatment, 5% underwent surgery, 21% XRT and 24% CT as initial therapy, at a median of 3.4 months from diagnosis. HPyinfection was recorded in 19%. Oncologic therapy was more frequent in patients who were younger, diagnosed after 2000, with stage >IE and no poor performance status (PS) indicator. Worse LSS was associated with increasing age, male sex, poor PS, gastrointestinal hemorrhage/perforation, stage >IE, B-symptoms, being widowed or prior malignancy. In the 347 stage IE patients who received XRT or CT within 2 years of diagnosis, XRT alone as initial therapy was associated with better CSS than CT (HR 0.27, 95%CI 0.13-0.55, P<0.001). OS did not differ. Among the 321 patients treated with CT, 45% received rituximab (R) alone, 43% cyclophosphamide-based and 10% fludarabine-based regimens. The median OS after CT was 5.8 years without significant difference between these groups. Compared with patients receiving R alone, LSS was worse for those treated with CT alone (HR=2.31, 95%CI 1.2-4.26, P=.007), but did not significantly differ for those treated with R+CT (HR=1.63, 95%CI 0.84-31.17, P=0.15). Conclusions: XRT may be a preferable choice in elderly patients with stage IE gastric MALT lymphoma. In those requiring CT, addition of CT to rituximab alone is not associated with improved LSS.