Final Report of Reduced Anthracycline Dose Intensity with the Addition of Dose Dense Rituximab in Children, Adolescents and Young Adults with De Novo Good Risk Mature B-Cell Non Hodgkin Lymphoma (B-NHL)

Background:

Previous studies have demonstrated excellent results with FAB/LMB86 chemotherapy alone and in combination with rituximab in children, adolescents and young adults with mature B-NHL. (Cairo et al, JCO 2012, Goldman et al, Leukemia, 2013, Goldman et al, BJH 2014) The intermediate risk FAB/LMB Group B arm consists of 180mg/m² of doxorubicin. This was reduced to 120mg/m² with the addition of dose-dense rituximab. Other standard NHL regimens more commonly used in young adults with advanced stage mature B-NHL, such as R-CHOP, have a total dose doxorubicin of 360mg/m². These approaches are associated with short term morbidities and long-term health conditions, including anthracycline induced cardiac toxicities. Dose-dense rituximab containing chemoimmunotherapy in high risk mature B-NHL has shown significant improvements in outcomes. We tested the hypothesis that rituximab can be used to even further reduce the burden of anthracycline from 120mg/m² to 50mg/m² in patients with good risk B-NHL.

Objective:

To safely reduce the burden of therapy by reducing the number of IT injections and reducing the total dose of doxorubicin from 120mg/m² to 50mg/m² with the addition of liposomal cytarabine and dose-dense rituximab to our prior chemotherapy backbone in children with good risk mature B-NHL.

Design/Methods:

Multi-institutional Phase II study (NCT01859819). Patients (3-31 years) with CD20+ B-NHL with good risk (FAB Group B GR=Stage I/II, Stage III with any LDH and Stage IV {BM tumor < 25%)}) were eligible. Staging was defined per the IPNHLSS as previously described. (Roselen et al, JCO 2015) All patients received FAB backbone chemotherapy with the addition of six rituximab (375mg/m²) doses; two doses prior to each of two induction courses and one dose prior to each of two consolidation courses. Cumulative doxorubicin was reduced from 120 to 50 mg/m² (25mg/m² per dose) total. After systemic methotrexate clearance, patients received age-based dosing of IT liposomal cytarabine resulting in a reduction of IT injections from nine to five. The primary outcome was safety and toxic deaths with an estimated 3-year survival above 90%, monitored by an independent DSMB. Response was defined per the IPNHLRC as previously described. (Sandlund et al, JCO 2015)

Results:

Twenty-five FAB Group B patients were enrolled at 5 treatment centers in the United States. Histology included DLBCL in 13 patients and Burkitt in 12 patients. Table 1. All patients had at least a 20% tumor decrease after the reduction phase. Two patients were upstaged to intensified Group C therapy after residual imaging findings post first consolidation. Therefore, 23/25 patients had a cumulative doxorubicin exposure of 50 mg/m² while the two patients who received augmented treatment had a total exposure of 170 mg/m². There were no serious adverse events reported with rituximab administration and no reported CNS or other toxicity reported with liposomal cytarabine intrathecal prophylaxis. During the two induction cycles there were no readmissions for febrile neutropenia or other causes and no reported grade III or higher mucositis. Follow up immune globulin levels on a smaller cohort of patients revealed median IgG levels of 821 (range, 362-1172) at a median follow up of 24 months. All patients are alive and in first remission with an EFS/OS = 100% at a median follow up of 4 years (range, 2-7yr). Figure 1. Echocardiograms revealed stable left ventricular function. Rituximab CSF levels were measured as we previously described and were extremely low (< 10µg/ml) compared to peak serum levels (250-400µg/ml).

Conclusions:

Our results demonstrate the feasibility of careful reduction of anthracycline dose intensity with the addition of dose-dense rituximab immunotherapy in children, adolescents and young adults with good risk mature B-NHL.

Our results demonstrate a 100% EFS/OS with a reduction to only 50mg/m² total dose of anthracycline. This is consistent with published standard of care outcomes utilizing much higher doses of 120-550mg/m² of doxorubicin. Our treatment strategy benefits good risk patients with mature B-NHL by using dose-dense rituximab to reduce the cumulative exposure of anthracycline associated short- and long-term toxicities as well as the number of required intrathecal injections. These excellent results require the investigation of this approach in a larger cohort in the future to confirm these preliminary findings.