Role Of Purging

MCL is particularly resistant to purging. 71 The efficacy of immunological purging was assessed by using poly-merase chain reaction (PCR) for minimal residual disease (MRD) on 26 MCL patients undergoing transplant. All patients had MRD detected by PCR after transplant irrespective of prior history of bone marrow involvement. This study demonstrated that reinfusion of stem cells with MRD was associated with a poor outcome. In addition, one study demonstrated that despite using anti-B-cell monoclonal antibody for ex vivo purging of the autograft, 88% of the autografts still had evidence of lymphomatous contamination.62 The use of in vivo purging using rituximab is promising, with evidence of clinical and molecular remis-sions.72 73 Gianni et al treated 28 patients with MCL younger than 60 years who completed at least 6 cycles of CHOP-like chemotherapy. Patients were treated with three cycles of cisplatin or doxorubicin-based debulking chemotherapy followed by high-dose sequential therapy with rituximab and ASCT. The 54-month OS and EFS rates were 89% and 79%, respectively as compared to rates for historical controls of 42% and 18%. Interestingly, clinical and molecular remission was found in 20/20 patients tested following in vivo purging, but not following debulking chemotherapy or following mobilization. Another study showed PCR negativity following transplant and in vivo purging with rituximab.74 In this study, patients were treated with chemotherapy and subsequently received high-dose cytosine arabinoside and rituximab as in-vivo purging. Twelve patients were evaluable for molecular remission. Ten of the 12 patients achieved PCR negativity posttransplant.

Two studies have suggested that posttransplant rit-uximab increases the clinical and molecular response rate of MCL patients receiving ASCT.75,76 In one study of advanced stage MCL, all patients who received post-transplant rituximab were alive without clinical or molecular relapse at 239 days posttransplant.75 The treatment was well tolerated and encouraging, albeit longer follow-up is needed.

Cumulatively, these approaches employing ritux-imab either in vivo for purging or posttransplant suggest that molecular and clinical remission may play a role in the long term outcome. Again, none of these studies have a long enough follow-up to assess the impact on OS.

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