Characterization of Exceptional Responders to Autologous Stem Cell Transplantation in Multiple Myeloma
Authors: Paquin Ashley , Gertz Morie A. , Chaudhry Hafsa , Kumar Shaji K. , Buadi Francis K. , Dispenzieri Angela , Dingli David , Hwa Yi , Fonder Amie , Hobbs Miriam , Hayman Suzanne R. , Zeldenrust Steven , Lust John A. , Russell Stephen J. , Leung Nelson , Kapoor Prashant , Go Ronald S. , Lin Yi , Gonsalves Wilson I , Kourelis Taxiarchis , Warsame Rahma , Kyle Robert A. , Rajkumar S. Vincent 
Published: October 2019

Aims: Autologous stem cell transplantation (ASCT) is an important component in the treatment of newly diagnosed multiple myeloma (MM). However, relapse following ASCT is considered almost inevitable, with a median time to progression (TTP) of approximately 23-26 months (without maintenance) and 40-46 months (with maintenance)(Attal MA et al. N Engl J Med 2012; 366:1782-1791; McCarthy PM et al. N Engl J Med 2012; 366:1770-1781). However, some patients can experience a prolonged period of remission with ASCT. The purpose of this study was to identify and characterize patients who have an exceptional response to upfront ASCT without maintenance therapy, and to determine the frequency of relapse in such patients.

Methods: We searched the Mayo Clinic Multiple Myeloma bone marrow transplant database for patients who were diagnosed with MM between Aug 1, 1988 to Jan 3, 2006, and underwent ASCT within 12 months of initial diagnosis. For the purposes of this study, we defined exceptional responders as patients who were free of progression for 96 months or more, which is 2-3 fold more than the median TTP expected in this population. Since maintenance therapy was not standard of care at the time, only a small minority (6) of patients with prolonged TTP had received maintenance therapy; these patients were excluded since the study was focused on exceptional response with ASCT alone. One patient who had a tandem autologous transplant was excluded.

Results: 509 patients underwent transplant during the study period. Of those, 46 (9%) met criteria for exceptional response. Twenty seven (59%) were female, 19 (41%) were male. Median age was 57.28 years, range, 31.9-73.0. Of 45 patients with response data available, the best response status was complete response or better in 32 patients (73.3%), VGPR in 4 patients (8.9%), and PR in 8 patients (17.7%). FISH data were available during the disease course for 41 patients. Of these, the majority, 28 patients (68.3%), had no abnormalities detected by the probes used; 3 patients (7.3%) had high risk cytogenetics (t(4;14) in 2 patients and t(14;16) in one patient) , 4 (9.8%) had trisomies; 6 patients had other isolated abnormalities. At last follow up, 23 patients have progressed (50%); 14 (30.4%) have died, including one who died without progression to MM. The median overall survival from time of diagnosis of the exceptional responders was 18.5 years, range 9.2-22 years. From the landmark time of 96 months, the median TTP was 6.2 years, range, 0.4-10.6 years (Figure 1); No plateau was seen in the TTP curve. From the landmark time of 96 months, the median OS was 10.5 years, range, 0.4-14 years.

Conclusions: We conclude that approximately 10% of patients with newly diagnosed myeloma have an exceptional response to a single ASCT without maintenance therapy. These patients have a remarkable overall survival, both from diagnosis and from the landmark time point where they are classified as having achieved an exceptional response. Although TTP from the landmark time point is excellent, with median TTP of 6.2 years, there appears to be no plateau in the curve indicating ongoing risk of relapse despite a prolonged period of disease stability. Exceptional responders tended to have normal FISH studies (likely an indicator of responsive, low-tumor burden disease), and nearly 20% achieved this state despite not attaining a complete response.

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Disclosures

Gertz: Research to Practice: Consultancy; Apellis: Consultancy; spectrum: Consultancy, Honoraria; Medscape: Consultancy; celgene: Consultancy; janssen: Consultancy; Teva: Consultancy; Abbvie: Consultancy; annexon: Consultancy; Ionis: Honoraria; Alnylam: Honoraria; Prothena: Honoraria; Amgen: Consultancy; Physicians Education Resource: Consultancy. Kumar:KITE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; KITE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Dispenzieri:Celgene, Takeda, Prothena, Jannsen, Pfizer, Alnylam, GSK: Research Funding. Dingli:Millennium Takeda: Research Funding; Millennium Takeda: Research Funding; Alexion Pharmaceuticals, Inc.: Other: Participates in the International PNH Registry (for Mayo Clinic, Rochester) for Alexion Pharmaceuticals, Inc.; Alexion Pharmaceuticals, Inc.: Other: Participates in the International PNH Registry (for Mayo Clinic, Rochester) for Alexion Pharmaceuticals, Inc.. Russell:Vyriad: Equity Ownership. Kapoor:Takeda: Research Funding; Celgene: Research Funding.