National trends in inpatient admissions following stereotactic radiosurgery and the in-hospital patient outcomes in the United States from 1998 to 2011

Abstract

Purpose: This study sought to examine trends in stereotactic radiosurgery (SRS) and in-hospital patient outcomes on a national level by utilizing national administrative data from the Nationwide Inpatient Sample (NIS) database.

Methods and materials: Using the NIS database, all discharges where patients underwent inpatient SRS were included in our study from 1998 - 2011 as designated by the ICD9-CM procedural codes. Trends in the utilization of primary and adjuvant SRS, in-hospital complications and mortality, and resource utilization were identified and analyzed.

Results: Our study included over 11,000 hospital discharges following admission for primary SRS or for adjuvant SRS following admission for surgery or other indication. The most popular indication for SRS continues to be treatment of intracranial metastatic disease (36.7%), but expansion to primary CNS lesions and other non-malignant pathology beyond trigeminal neuralgia has occurred over the past decade. Second, inpatient admissions for primary SRS have declined by 65.9% over this same period of time. Finally, as inpatient admissions for SRS become less frequent, the complexity and severity of illness seen in admitted patients has increased over time with an increase in the average comorbidity score from 1.25 in the year 2002 to 2.29 in 2011, and an increase in over-all in-hospital complication rate of 2.8 times over the entire study period.

Conclusions: As the practice of SRS continues to evolve, we have seen several trends in associated hospital admissions. Overall, the number of inpatient admissions for primary SRS has declined while adjuvant applications have remained stable. Over the same period, there has been associated increase in complication rate, length of stay, and mortality in inpatients. These associations may be explained by an increase in the comorbidity-load of admitted patients as more high-risk patients are selected for admission at inpatient centers while more stable patients are increasingly being referred to outpatient centers.

Keywords: Nationwide Inpatient Sample; complications; mortality; radiosurgery outcomes; stereotactic radiosurgery; usage trends.

Figure 1

Stereotactic radiosurgery cases per year. The number of admitted inpatients for primary stereotactic radiosurgery has declined over time, from 695 observed NIS cases in 1998 to 237 cases in 2011. Two notable drops in caseload are noted to begin in 1999 and 2003.

Figure 2

Comorbidity and illness burden correlate with increasing complication rates. A) The mean comorbidity score has increased over time from an average 1.25 per patient in 2002 to 2.29 in 2011. B) The overall in-hospital complication rate has also increased over time from 4.5% in 1998 to 12.7% in 2011. (red) Mortality rate over this same period has remained stable from 2.29% in 1998 to 2.79% in 2011. (blue) C) Illness burden predictors of disease severity (red) and pre-operative mortality risk predictors (blue), which were also initiated in the NIS database beginning in 2002, have also increased from 1.9 and 1.51 respectively in 2002 to 2.45 and 2.21 in 2011.

Figure 3

Mean length of stay and mean charges. A) The mean length of stay has shown considerable increase on a year-to-year basis from 4.3 days in 1998 to 7.8 days in 2011 (p < .05). B) Mean hospital charges were $50,200 between 1998 and 2011, however the inflation-adjusted mean hospital charges have increased over time from $36,583 in 1998 to $110,497 in 2011 (p < .05).

Supplemental Figure 1

Routine and non-routine discharge rates. A) Routine discharges accounted for 82.3% of discharges throughout the entire time period but has decreased over time from 84.8% in 1998 to 58.9% in 2011 (p < .05). B) The proportion of patients discharged with home health care (blue) or transferred to other subacute facilities (red) have both increased from 2.8% and 9.6%, respectively in 1998 to 15.6% and 21.4% in 2011 (p < .05).