Autologous Hematopoietic Stem Cell Transplantation Overcomes Primary Refractory Disease in Multiple Myeloma Patients Treated with Novel Agents

Introduction:

Autologous hematopoietic stem cell transplantation (Auto HSCT) has been shown to prolong progression free (PFS) and overall survival (OS) in patients with multiple myeloma (MM), with the depth of response pre-transplant previously correlated with PFS, but not OS. Even in patients receiving proteasome inhibition and immunomodulatory agents as induction, up to 25% of newly diagnosed patients achieve less than a partial response (PR). We aimed to evaluate outcomes after Auto HSCT for patients with primary refractory MM.

Methods:

Between 1/2009 and 12/2012, we identified 95 newly diagnosed symptomatic MM patients treated at our institution with novel agent induction regimens and upfront Auto HSCT. Based on IMWG criteria, patients were separated into those achieving >= PR (CR, VGPR, PR) and those who are primary refractory (PrRef) as defined by stable or progressive disease (SD/PD) to first line therapy. Characteristics were compared by the Fisher's Exact test. PFS and OS were calculated in a landmark analysis from transplant and estimated by Kaplan-Meier methods and compared by the log rank test.

Results:

Sixteen patients (17%) had PrRef disease, with a median age of 53 vs 59 yrs in those who achieved >=PR (p=0.04). Demographic and clinical characteristics were otherwise not statistically different between the two groups: 56 vs 65% were male; 69 vs 80% Caucasian; 69 vs 48% had ISS Stage I disease with 19 vs 14% having high risk cytogenetics; 81 vs 84% had lytic lesions; and 31 vs 51% had extramedullary disease at diagnosis in PrRef pts vs >PR pts, respectively. All patients received induction regimens including either bortezomib (44 vs 38%), lenalidomide (31 vs 24%), or both (25 vs 37%) (p=0.68). Compared with 32% of >=PR pts, 94% of the PrRef pts were treated with additional therapy prior to Auto HSCT (p<0.001), with 5/15 achieving VGPR, 6/15 PR, and 4/15 SD/PD prior to Auto HSCT. Tandem Auto HSCT was performed in two PrRef vs one >= PR patient. Response to Auto HSCT was a 38 vs 58%, 25 vs 25%, 38 vs 14%, and 0 vs 4% for CR, VGPR, PR, and SD/PD, in PrRef vs responding pts respectively (p=0.19). Maintenance therapy, primarily with lenalidomide, was given to 69 vs 78% (p=0.52). Median PFS from transplant was 41 months (95% CI 16 - not reached ) in PrRef pts compared to 53 months, (95%CI: 31 - not reached) in >=PR pts (p=0.51). With a median follow-up of 36.5 months (range 9.5-63 months) in surviving patients, median OS from transplant was not reached in either group (p=0.77)(Figures 1 and 2). For the PrRef pts, 3-yr OS from transplant was 77% (95%CI 43-92%) compared to 87% (95%CI 77-93%) in >=PR pts.

Conclusion:

A small portion of MM patients have primary refractory disease after induction therapy with bortezomib and lenalidomide. Demographic and disease characteristics, other than age, were not able to differentiate these patients. However, Auto HSCT was an effective therapy regardless of response to novel agent based induction therapy.

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