Serum LDH predicts response rate, response duration, and survival of patients (pts) with relapsed/refractory non-Hodgkin’s lymphoma (NHL) treated with 131I-tositumomab (131I-Tab) or 90Y ibritumomab tiuxetan (90Y-Iab) radioimmunotherapy (RIT)

Abstract

17520 Background: Although both 131I-Tab and 90Y-Iab are approved for treatment of pts with relapsed or refractory low-grade, follicular, or transformed NHL, a prospective randomized comparison of these two forms of RIT has not been performed. We retrospectively reviewed our experience using either agent in pts with NHL. Methods: Sixty-one pts with NHL who were treated with a single course of 131I-Tab (N = 22) or 90Y-Iab (N = 39) between 1999 and 2005 were included in this analysis. The median age was 61 y (range 21–83 y) and the median number of prior therapies was 5 (range 1–13). Overall, 27 pts had indolent NHL (20 follicular grade 1/2, 4 small lymphocytic, and 3 marginal zone), while 34 pts had aggressive NHL (22 diffuse large cell, 10 mantle cell, and 2 follicular grade 3). Among pts, 75% had stage III/IV disease, 52% had an elevated serum LDH, and 38% had bulky disease (>5 cm). These characteristics were similar for pts receiving either 131I-Tab or 90Y-Iab, with the exception of elevated serum LDH (64% vs. 33%, p = 0.02). Median follow up was 21 mos (range 3–55). Results: The overall response rate (ORR) was 44% with complete response (CR) in 21% of pts. The median time to progression (TTP) was 5 mos for all pts, 9 mos for responders, and 14 mos for CRs (range 4–55). Patients with indolent NHL had no difference in ORR, CR, or TTP from pts with aggressive NHL, but had a significantly longer OS (HR 0.37, p = 0.01). Elevated LDH was the only significant predictor of ORR (31% vs. 57%, p = 0.04). In multivariable analysis, elevated LDH was adversely associated with TTP (HR 2.0, p = 0.02) and OS (HR 2.7, p = 0.02) among both subgroups of NHL. We did not discern a difference in ORR, CR, TTP, or OS between 131I-Tab and 90Y-Iab, even when stratifying for serum LDH. Conclusions: RIT produced high response rates in heavily pre-treated pts with indolent or aggressive NHL. Elevated LDH is the most significant prognostic factor for ORR, TTP and OS in this population. Patients with an elevated LDH should be considered for alternative treatment approaches or clinical trials, including RIT in combination with chemotherapy or transplant. [Table: see text]