Autologous Hematopoietic Stem Cell Transplantation (Auto-HCT) for Multiple Myeloma (MM) in the Inpatient (Inpt) Vs. Outpatient (Outpt) Settings: Impact of Hematopoietic Stem Cell Comorbidity Index (HCT-CI)

Introduction: High-dose chemotherapy (HDC) followed by auto-HCT can be performed in the outpt setting in selected pts and may be as safe and more cost effective than in the inpt setting. We evaluated the role of HCT-CI on the characteristics and outcomes of pts with MM who underwent auto-HCT in both inpt and outpt settings between January 2008 and December 2012 at our institution.

 

Methods: We identified a total of 1046 pts, with 669 transplanted as inpts and 377 as outpts. Primary endpoints were incidence of unscheduled admissions, treatment-related mortality (TRM), grade 2-4 adverse events (AEs), defined by the National Cancer Institute's Common Terminology Criteria, version 4, and average cost of auto-HCT in both inpt and outpt groups. Secondary endpoints were overall response (OR) rates, progression-free survival (PFS), and overall survival (OS).

 

Results: Median age at auto-HCT was 62 (range, 31-82) in inpts and 58 (range, 34-78) years in outpts, (p<0.001). HCT-CI score was ≥3 in 55% inpts vs 45% outpts (p=.003). There was no significant difference in baseline cytogenetic abormalities, serum LDH or ISS stage II/III between the 2 groups. Forty-four (6.6%) inpts and 7 (2%) outpts had serum creatinine of ≥2 mg/dL (p=<0.001). Twenty-nine percent of inpts vs. 21% of outpts had relapsed disease at auto-HCT (p=0.02). Median follow up in inpts vs. outpts was 14 and 15 months, respectively. One-hundred day TRM was 1.5% in inpts vs. 0.3% in outpts (p=0.09). Grade 2-4 AEs were seen in 552 (83%) inpts vs. 277 (73%) outpts, (p=0.001); grade 3-4 in 359 (54%) inpts vs. 163 (43%) outpts, (p=0.001); and grade 4 in 19 (3%) inpts vs. 6 (2%) outpts, (p=0.2). OR rates were significantly better in outpts, with 364 (96.5%) outpts with ≥PR vs. 599 (89%) inpts (p<0.001). Subsequent unscheduled hospitalizations were required in 208 (55%) outpts, with neutropenic or non-neutropenic fever being the most common reason (157 pts: 42%). On multivariate analyses, an HCT-CI score of >2 and relapsed disease at auto-HCT were associated with increased incidence of unscheduled hospitalization. Outpts had significantly longer 2-year PFS (60% vs. 50%, p=0.005, HR 0.7, 95% CI 0.6-0.9) and OS (83% vs. 77%, p=0.01, HR 0.6, 95% CI 04-0.9). The average cost of auto-HCT from the date of original consult to day +30 was $416,154 for inpts and $292,572 for outpts.

 

Discussion: In this study, pts selected for auto-HCT in the outpt setting were younger, had a lower HCT-CI score and a significantly better renal function at diagnosis. A lower HCT-CI score and auto-HCT in first remission predict a lower risk of unscheduled hospitalization, with a cost savings of approximately $125,000 for those who received auto-HCT in the outpt setting. Appropriately selected pts with MM can safely undergo auto-HCT in the outpt setting without any significant increase in toxicity or TRM, and a significant decrease in transplant costs.