Pre-emptive treatment with rituximab of molecular relapse after autologous stem cell transplantation in mantle cell lymphoma.

PURPOSE: Minimal residual disease (MRD) is predictive of clinical progression in mantle-cell lymphoma (MCL). According to the Nordic MCL-2 protocol we prospectively analyzed the efficacy of pre-emptive treatment using rituximab to MCL patients in molecular relapse after autologous stem cell transplantation (ASCT). PATIENTS AND MATERIALS: MCL patients enrolled onto the study, who had polymerase chain reaction (PCR) detectable molecular markers and underwent ASCT, were followed with serial PCR assessments of MRD in consecutive bone marrow and peripheral blood samples after ASCT. In case of molecular relapse with increasing MRD levels, patients were offered pre-emptive treatment with rituximab 375 mg/m(2) weekly for 4 weeks. RESULTS: Of 160 MCL patients enrolled, 145 underwent ASCT, of whom 78 had a molecular marker. Of these, 74 were in complete remission (CR) and four had progressive disease after ASCT. Of the CR patients, 36 underwent a molecular relapse up to 6 years (mean, 18.5 months) after ASCT. Ten patients did not receive pre-emptive treatment mainly due to a simultaneous molecular and clinical relapse, while 26 patients underwent pre-emptive treatment leading to reinduction of molecular remission in 92%. Median molecular and clinical relapse-free survival after pre-emptive treatment were 1.5 and 3.7 years, respectively. Of the 38 patients who remain in molecular remission for now for a median of 3.3 years (range, 0.4 to 6.6 years), 33 are still in clinical CR. CONCLUSION: Molecular relapse may occur many years after ASCT in MCL, and PCR based pre-emptive treatment using rituximab is feasible, reinduce molecular remission, and may prevent clinical relapse.