Phase 1/2 study of fractionated (131)I-rituximab in low-grade B-cell lymphoma: the effect of prior rituximab dosing and tumor burden on subsequent radioimmunotherapy.

The effect of induction therapy with multiple doses of rituximab on the subsequent efficacy and toxicity of anti-CD20 radioimmunotherapy is unknown. We evaluated a novel protocol using 4 weekly infusions of 375 mg/m(2) rituximab followed by 2 fractions of (131)I-rituximab, preceded by a 100-mg/m(2) predose of rituximab, in relapsed indolent B-cell lymphoma. Induction therapy with rituximab significantly increased the effective half-life of (131)I-rituximab (P = .003) and high serum levels of rituximab after induction therapy correlated with increased effective half-life of the radioimmunoconjugate (P = .009). Patients with large tumor burdens experienced significant increases in the effective half-life of (131)I-rituximab between delivery of the first and second fractions (P = .007). Induction therapy with multiple doses of rituximab did not appear to compromise the clinical efficacy or increase toxicity of subsequent (131)I-rituximab radioimmunotherapy. The overall response rate was 94%, with complete response rate 50%. The median time to progression was 20 months, significantly longer than for the last qualifying chemotherapy (P = .001). Fractionation of (131)I-rituximab allowed cumulative whole-body doses of more than 120 cGy, approximately 60% greater than those previously achieved with a single administration of a murine radioimmunconjugate, to be delivered without significant hematologic toxicity.

Relation of hypoxia-inducible factor-2 alpha (HIF-2 alpha) expression in tumor-infiltrative macrophages to tumor angiogenesis and the oxidative thymidine phosphorylase pathway in Human breast cancer.

Tumor-associated macrophages (TAMs) produce angiogenic factors and in breast cancer are associated with high vascular grade and poor survival. TAMs preferentially migrate to hypoxic areas within tumors and strongly express hypoxia-inducible factor (HIF)-2 alpha. This study examined whether HIF-2 alpha was involved in TAM angiogenic activation by correlating its expression with tumor microvessel density as a marker of angiogenesis, and other tumor variables, in a series of human primary invasive breast carcinomas. A correlation was found between high TAM HIF-2 alpha and high tumor vascularity (P < 0.0001), as well as high tumor grade (P = 0.007). The relation of HIF-2 alpha expression to a recently described oxygen-dependent pathway of angiogenesis was also studied, and an inverse relationship was found between TAM HIF-2 alpha and tumor thymidine phosphorylase expression (P = 0.02). These results suggest that TAM HIF-2 signaling may be a useful target for future antiangiogenic strategies but show that tumors use both oxygen-dependent and oxygen deficiency-regulated pathways for angiogenesis. Thus, combined blockade of pathways and careful assessment of these pathways in trials are necessary.