Gordon, Leo I.

PURPOSE: Yttrium-90 ibritumomab tiuxetan (IDEC-Y2B8) is a murine immunoglobulin G1 kappa monoclonal antibody that covalently binds MX-DTPA (tiuxetan), which chelates the radioisotope yttrium-90. The antibody targets CD20, a B-lymphocyte antigen. A multicenter phase I/II trial was conducted to compare two doses of unlabeled rituximab given before radiolabeled antibody, to determine the maximum-tolerated single dose of IDEC-Y2B8 that could be administered without stem-cell support, and to evaluate safety and efficacy.PATIENTS AND METHODS: Eligible patients had relapsed or refractory (two prior regimens or anthracycline if low-grade disease) CD20+B-cell low-grade, intermediate-grade, or mantle-cell non-Hodgkin's lymphoma (NHL). There was no limit on bulky disease, and 59% had at least one mass ≥ 5 cm.RESULTS: The maximum-tolerated dose was 0.4 mCi/kg IDEC-Y2B8 (0.3 mCi/kg for patients with baseline platelet counts 100 to 149,000/μL). The overall response rate for the intent-to-treat population (n = 51) was 67% (26% complete response [CR]; 41% partial response [PR]); for low-grade disease (n = 34), 82% (26% CR; 56% PR); for intermediate-grade disease (n = 14), 43%; and for mantle-cell disease (n = 3), 0%. Responses occurred in patients with bulky disease (≥ 7 cm; 41%) and splenomegaly (50%). Kaplan-Meier estimate of time to disease progression in responders and duration of response is 12.9+ months and 11.7+ months, respectively. Adverse events were primarily hematologic and correlated with baseline extent of marrow involvement with NHL and baseline platelet count. One patient (2%) developed an anti-antibody response (human antichimeric antibody/human antimouse antibody).CONCLUSION: These phase I/II data demonstrate that IDEC-Y2B8 radioimmunotherapy is a safe and effective alternative for outpatient therapy of patients with relapsed or refractory NHL. A phase III study is ongoing.

AbstractUniformly adopted response criteria are essential for assessment of therapies incorporating conventional chemotherapy and chemoimmunotherapy regimens. Recently, immunomodulatory agents, such as immune checkpoint inhibitors, have demonstrated impressive activity in a broad range of lymphoma histologies. However, these agents may be associated with clinical and imaging findings during treatment suggestive of progressive disease (PD) despite evidence of clinical benefit (eg, tumor flare or pseudo-progression). Considering this finding as PD could lead to patients being prematurely removed from a treatment from which they actually stand to benefit. This phenomenon has been well described with checkpoint blockade therapy in solid tumors and anecdotally seen in lymphoma as well. To address this issue in the context of lymphoma immunomodulatory therapy, a workshop was convened to provide provisional recommendations to modify current response criteria in patients receiving these and future agents in clinical trials. The term “indeterminate response” was introduced to identify such lesions until confirmed as flare/pseudo-progression or true PD by either biopsy or subsequent imaging.

BACKGROUNDIn an ECOG‐ACRIN Cancer Research Group study (E1496), maintenance rituximab (MR) was reported to prolong progression‐free survival (PFS) in comparison with observation (OBS) alone in patients with indolent lymphoma after induction chemotherapy. Here the long‐term follow‐up of the same patient cohort is presented.METHODSPatients with indolent lymphoma received induction chemotherapy with cyclophosphamide, vincristine, and prednisone (CVP). Patients with stable disease or a better response were then randomized to weekly rituximab (375 mg/m2 × 4 doses) every 6 months for 2 years (MR) or to OBS. The primary endpoint was PFS; the secondary endpoints were overall survival (OS), response rate, and toxicities.RESULTSOf the 387 patients who initially received CVP induction, 158 were randomized to MR, and 153 were randomized to OBS. After a median follow‐up of 11.5 years, patients on MR had longer median PFS (4.8 years) than patients on OBS (1.3 years; hazard ratio [HR], 0.49; P < .0001). However, there was no difference in OS between MR and OBS (10‐year OS, 67% vs 59%; median OS, 13.5 years vs not reached; HR, 0.91; P = .69). Other than MR, only minimal residual disease after induction therapy was significantly associated with PFS on multivariate analysis (HR, 0.71; P = .02). A low initial tumor burden, minimal residual disease, follicular histology, a low Follicular Lymphoma International Prognostic Index score, and female sex were associated with longer OS. There was no increase in the rate of second primary malignancies with MR vs OBS.CONCLUSIONSWith long‐term follow‐up, MR did not influence OS. The PFS benefit was maintained. MR should be considered optional for patients with indolent B‐cell lymphoma. Cancer 2016;122:2996‐3004. © 2016 American Cancer Society.

SummaryThe International Prognostic Score (IPS‐7) is the most commonly used risk stratification tool for advanced Hodgkin lymphoma (HL), however recent studies suggest the IPS‐7 is less discriminating due to improved outcomes with contemporary therapy. We evaluated the seven variables for IPS‐7 recorded at study entry for 854 patients enrolled on Eastern Cooperative Oncology Group 2496 trial. Univariate and multivariate Cox models were used to assess their prognostic ability for freedom from progression (FFP) and overall survival (OS). The IPS‐7 remained prognostic however its prognostic range has narrowed. On multivariate analysis, two factors (age, stage) remained significant for FFP and three factors (age, stage, haemoglobin level) for OS. An alternative prognostic index, the IPS‐3, was constructed using age, stage and haemoglobin level, which provided four distinct risk groups [FFP (P = 0·0001) and OS (P < 0·0001)]. IPS‐3 outperformed the IPS‐7 on risk prediction for both FFP and OS by model fit and discrimination criteria. Using reclassification calibration, 18% of IPS‐7 low risk patients were re‐classified as intermediate risk and 13% of IPS‐7 intermediate risk patients as low risk. For patients with advanced HL, the IPS‐3 may provide a simpler and more accurate framework for risk assessment in the modern era. Validation of these findings in other large data sets is planned.

Rituximab improves outcomes for persons with lymphoproliferative disorders and is increasingly used to treat immune-mediated illnesses. Recent reports describe 2 patients with systemic lupus erythematosus and 1 with rheumatoid arthritis who developed progressive multifocal leukoencephalopathy (PML) after rituximab treatment. We reviewed PML case descriptions among patients treated with rituximab from the Food and Drug Administration, the manufacturer, physicians, and a literature review from 1997 to 2008. Overall, 52 patients with lymphoproliferative disorders, 2 patients with systemic lupus erythematosus, 1 patient with rheumatoid arthritis, 1 patient with an idiopathic autoimmune pancytopenia, and 1 patient with immune thrombocytopenia developed PML after treatment with rituximab and other agents. Other treatments included hematopoietic stem cell transplantation (7 patients), purine analogs (26 patients), or alkylating agents (39 patients). One patient with an autoimmune hemolytic anemia developed PML after treatment with corticosteroids and rituximab, and 1 patient with an autoimmune pancytopenia developed PML after treatment with corticosteroids, azathioprine, and rituximab. Median time from last rituximab dose to PML diagnosis was 5.5 months. Median time to death after PML diagnosis was 2.0 months. The case-fatality rate was 90%. Awareness is needed of the potential for PML among rituximab-treated persons.

Purpose To determine the maximum-tolerated radiation-absorbed dose (RAD) to critical organs delivered by yttrium-90 (90Y) ibritumomab tiuxetan in combination with high-dose carmustine, etoposide, cytarabine, and melphalan (BEAM) chemotherapy with autologous transplantation. Patients and Methods Eligible patients had relapsed or refractory CD20+ non-Hodgkin's lymphoma (NHL). Individualized 90Y activities were based on dosimetry and were calculated to deliver cohort-defined RAD (1 to 17 Gy) to critical organs with three to six patients per cohort. The therapeutic dose of 90Y ibritumomab tiuxetan was followed by high-dose BEAM and autologous transplantation. Results Forty-four patients were treated. Thirty percent of patients had achieved less than a partial remission to their most recent therapy and would not have been eligible for autologous transplantation at most centers. The toxicity profile was similar to that associated with high-dose BEAM chemotherapy. Two dose-limiting toxicities occurred at the 17 Gy dose level, which made 15 Gy the recommended maximum-tolerated RAD. Although eight patients received at least twice the conventional dose of 0.4 mCi/kg, a weight-based strategy at 0.8 mCi/kg would have resulted in a wide range of RAD; nearly 25% of patient cases would have received 17 Gy or more, and many would have received less than 10 Gy. With a median follow-up of 33 months for all patients, the estimated 3-year progression-free and overall survivals were 43% and 60%, respectively. Conclusion Dose-escalated 90Y ibritumomab tiuxetan may be safely combined with high-dose BEAM with autologous transplantation and has the potential to be more effective than standard-dose radioimmunotherapy. Careful dosimetry is required to avoid toxicity and undertreatment.