SAN DIEGO – Rituximab can at least temporarily vanquish minimal residual disease (MRD) in mantle cell lymphoma (MCL) patients who relapse after induction therapy and autologous stem cell transplantation (ASCT), researchers reported at the annual meeting of the American Society of Hematology.
Of 58 patients whose MCL relapsed after induction therapy and ASCT, 82% converted back to an MRD-negative state after receiving 4 weekly doses of rituximab (375 mg/m2), Arne Kolstad, MD, PhD, and his associates. The data “strongly suggest that preemptive rituximab treatment delayed clinical relapse in MCL,” they wrote in their abstract. They recommended molecular and clinical monitoring after ASCT, not only “as an alternative to maintenance therapy for all MCL patients” but to identify MRD-positive candidates for clinical trials.
The study was an analysis of the Nordic Lymphoma Group phase II MCL2 and MCL3 trials (NTC 00514475), in which patients received six alternating cycles of R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab) and R-Ara-C (rituximab-cytarabine). followed by high-dose ASCT. In MCL3, responders who fell short of complete remission also received intensification with yttium-90 ibritumomab tiuxetan (0.4 mCi/kg) 1 week before treatment with BEAM/C (carmustine, etoposide, cytarabine, and melphalan or cyclophosphamide). Patients were evaluated 2-3 months after completing ASCT, and then every 6 months for 5 years or until relapse. Survivors were followed for a median of 8.5 years, noted Dr. Kolstad, who is with Oslo University Hospital in Norway.
Among 183 patients who underwent polymerase chain reaction–based testing for markers of MRD, median time to molecular relapse was 55 months. However, the relapse-free survival curve did not plateau – patients in all risk groups continued to relapse 5-10 years after undergoing ASCT, the researchers said. “Hence, it is fair to consider MCL as a chronic incurable lymphoma entity, and novel approaches will be necessary to change the natural course of this disease,” they wrote.
After controlling for potential confounders, significant predictors of molecular relapse included high MCL international prognostic index at diagnosis (hazard ratio, 1.9; 95% confidence interval 1.4-2.7; P = .0001) and detection of MRD before patients underwent ASCT (HR, 2.5; 95% CI, 1.5-4.1; P = .0005). Minimal residual disease predicted clinical relapse and shorter survival (P less than .001 for both associations). In contrast, the 86 patients who remained in continuous molecular remission had a 76% chance of having at least a 10-year clinical remission, the investigators said.
Minimal residual disease was assessed by testing bone marrow and blood samples with combined standard nested and quantitative real-time polymerase chain reaction (PCR) for Bcl-1 or IgH rearrangement. They defined molecular relapse as conversion from a negative to a positive result on standard nested PCR, or, for patients who were MRD positive after ASCT, as a more than fivefold rise in real-time quantitative PCR levels in two consecutive bone marrow samples.
Oslo University sponsored the trials. Dr. Kolstad reported ties to Nordic Nanovector, Bayer Schering Pharma, Merck, and Roche.