Introduction:

Autologous stem cell transplant (ASCT) is the standard of care for eligible patients with multiple myeloma (MM). With the considerable advances in supportive care for patients receiving ASCT, many institutions now perform ASCT for MM on a completely outpatient basis. The National Inpatient Sample (NIS) tracks all inpatient hospitalizations in the United States. Hence, using the NIS, hospital admissions for MM patients undergoing ASCT and their mortality over a period of time can be tracked. We interrogated the NIS to analyze characteristics of these patients.

Methods:

From the years of 2002 to 2014, admissions for ASCT for MM patients were identified using the NIS via procedural ICD 9 codes for autologous bone marrow transplantation and MM. Annual trends in mortality, hospital length of stay, and costs of admission were assessed with a linear regression analysis. Chronic co-morbid conditions were investigated for associations with in-hospital mortality in the years of 2013 and 2014 using univariate logistic regression analysis.

Results:

A total weighted estimate of inpatient admissions for ASCT among MM patients totaled 47,253 (unweighted N=10,231) between the years of 2002 and 2014. Annual inpatient transplants increased from 1,601 in 2002 to 5,170 in 2014. Publicly available data from the Center for International Blood and Marrow Transplant research indicates that the number of ASCT for MM in the US were approximately 2100 in 2002, compared to 7500 patients in 2014, hence the number of inpatient transplants as a ratio of overall transplants decreased significantly from 76.2% in 2002 to 68.9% in 2014 (p <0.001)

The in-hospital mortality decreased non-significantly from 0.018% in 2002 to 0.007% in 2014 (p=0.077). The mean length of stay decreased only slightly from 18.8 days in 2002 to 17.3 days in 2014 (p=0.005), Costs of admission increased from $97,391 in 2002 to$184,002 in 2014 (p <0.001), despite the minimal change in the length of stay.

Amongst common co-morbidities, significant associations with in-hospital mortality were seen in congestive heart failure (odds ratio (OR) = 4.60), weight loss (OR=4.15), chronic renal disease (OR=4.99) and valvular heart disease (OR=6.16) (Table 1).

Conclusion:

The proportion of patients receiving ASCT for MM as an outpatient has increased significantly from 2002 to 2014. Among those patients admitted for ASCT, the average length of stay has changed minimally, but the average cost of hospitalization has almost doubled. The presence of co-morbid conditions including congestive heart failure, previous weight loss, chronic renal disease, and valvular disease are significantly associated with a higher incidence of in-hospital mortality for patients with MM undergoing ASCT and likely drive up the cost for inpatient stays. As institutions continue to shift ASCT for MM from an inpatient to outpatient setting, further analysis of the inpatient drivers of cost is needed, as well as a cautious understanding of risk factors for mortality in this setting.

Disclosures

No relevant conflicts of interest to declare.

## Author notes

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Asterisk with author names denotes non-ASH members.