Hospitalization Costs for Radical Prostatectomy Attributable to Robotic Surgery

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1 EUROPEAN UROLOGY 64 (2013) available at journal homepage: Platinum Priority Prostate Cancer Editorial by Yair Lotan on pp of this issue Hospitalization Costs for Radical Prostatectomy Attributable to Robotic Surgery Simon P. Kim a, *, Nilay D. Shah b, R. Jeffrey Karnes a, Christopher J. Weight c, Nathan D. Shippee d, Leona C. Han b, Stephen A. Boorjian a, Marc C. Smaldone e, Igor Frank a, Matthew T. Gettman a, Matthew K. Tollefson a, R. Houston Thompson a a Mayo Clinic, Department of Urology, Rochester, MN, USA; b Mayo Clinic, Division of Health Care Policy and Research, Rochester, MN, USA; c University of Minnesota, Department of Urology, Minneapolis, MN, USA; d University of Minnesota, Division of Health Policy and Management, Minneapolis, MN, USA; e Fox Chase Cancer Center, Department of Surgery, Philadelphia, PA, USA Article info Article history: Accepted August 12, 2012 Published online ahead of print on August 20, 2012 Keywords: Comparative effectiveness Costs Outcomes Prostate cancer Radical prostatectomy Robotic surgery Abstract Background: With health technology innovation responsible for higher health care costs, it is essential to have accurate estimates regarding the differential costs between robot-assisted radical prostatectomy (RARP) and open radical prostatectomy (ORP). Objective: To describe the total hospitalization costs attributable to robotic and open surgery for radical prostatectomy (RP). Design, setting, and participants: Using a population-based cohort by merging the Nationwide Inpatient Sample (NIS) and the American Hospital Association (AHA) survey from 2006 to 2008, we identified prostate cancer patients who underwent RP. Interventions: ORP and RARP. Outcome measurements and statistical analysis: The primary outcome was total hospitalization costs adjusted to year 2008 US dollars. Generalized estimating equations were used to identify patient and hospital characteristics associated with total hospitalization costs and to estimate costs of ORP and RARP adjusted for case mix and hospital teaching status, location, and annual case volume. Results and limitations: Overall, (68.5%) patients were surgically treated with RARP, and 9413 (31.5%) patients underwent ORP. Compared to ORP, patients undergoing RARP had shorter median length of stay (1 d vs 2 d; p < 0.001) and were less likely to experience any postoperative complications (8.2% vs 11.3%; p < 0.001). However, patients undergoing RARP had higher median hospitalization costs ($ vs $8862; p < 0.001). After adjusting for patient and hospital features, RARP was associated with higher total hospitalization costs compared to ORP ($ vs $9390; p < 0.001). Our results are limited by a study design using retrospective population-based data. Conclusions: Despite RARP having lower complications and shorter length of stay than ORP, total hospitalization costs are higher for patients treated with RARP compared with those treated with ORP. # 2012 European Association of Urology. Published by Elsevier B.V. All rights reserved. * Corresponding author. Mayo Clinic, Department of Urology, 200 First Street SW, Rochester, MN 55905, USA. address: Kim.Simon@mayo.edu (S.P. Kim). 1. Introduction With US health care costs of $2.6 trillion in 2010 [1], there is greater scrutiny to critically examine different treatments for patient-centered outcomes and health care value. Comparative effectiveness research (CER) represents one way to appraise various treatments for relative differences in clinical outcomes to better inform treatment decisions /$ see back matter # 2012 European Association of Urology. Published by Elsevier B.V. All rights reserved.

2 12 EUROPEAN UROLOGY 64 (2013) for patients, physicians, and policymakers. An ancillary aim of CER is to help control the growth in health care spending [2], in particular for hospitalizations given the $814 billion annual expenditure and significant variations of surgical costs in the United States [1,3]. Other important drivers of higher costs include hospital complications and health technology innovation [4,5]. With prostate cancer (PCa) remaining the most commonly diagnosed, noncutaneous, male malignancy with incident cases in 2011 [6], $12 billion are spent on this prevalent cancer each year in the United States [7]. CER is therefore applicable to PCa, given the rapid adoption of more costly technology innovations, such as robotic surgery and intensity-modulated radiation therapy, absent supporting level 1 evidence [8]. Since its introduction in 2000, robot-assisted radical prostatectomy (RARP) has been rapidly adopted, supplanting conventional open radical prostatectomy (ORP) to a large degree [8 10]. The benefits of RARP include decreased length of stay (LOS) and blood loss with concomitant diminished need for blood transfusions [10,11], although the differences in oncologic outcome have been mixed and, to date, the two different surgical approaches have not been rigorously evaluated by any clinical trials [11]. In this context, RARP may be subject to greater scrutiny, especially since robotic surgery may add approximately $1 billion annually in health care spending [12]. Previous studies suggest that the differential cost may range from $200 to $2000 between ORP and RARP [8,13 19]. However, these studies may not fully capture the cost differential since they either rely on single-institution series, or populationbased data from Medicare beneficiaries, in which case the US Centers for Medicare and Medicaid Services (CMS) reimburses RARP at the same rate as ORP. Therefore, we sought to describe the incremental hospitalizations costs for patients undergoing radical prostatectomy (RP) attributable to robotic surgery using population-level data. 2. Methods 2.1. Study population Data for all patients who underwent RP for PCa were generated by merging two data sources: the Nationwide Inpatient Sample (NIS) and the American Hospital Association (AHA) Annual Survey. The NIS represents the largest all-payer inpatient database in the United States and captures approximately 20% of all hospital admissions [20]. The AHA conducts an annual survey of a nationally representative sample of approximately 5000 hospitals in the United States [21]. To identify the analytic cohort, we used a similar methodology described previously from International Classification of Disease Modification 9th edition (ICD-9) codes from hospital claims data in the NIS from 2006 to 2008 [10,22]. We selected elective cases with a primary diagnostic ICD-9 code for PCa (185) and concomitant primary or secondary procedure codes for RP (60.5) from the NIS. We further limited our cohort by excluding pediatric patients (n = 3) Patient and hospital variables Patient variables included in our analysis were age, race, health insurance, median income by zip code, LOS, and year of surgery. Secondary diagnostic codes were used to define an Elixhauser comorbidity index [23]. We also evaluated hospital teaching status, location, region, and annual case volume as independent hospital-level variables. The unique hospital identifier was used to enumerate annual case-volume quartiles by average number of RPs performed. Another clinical variable assessed in our analysis was postoperative complications. We used the NIS to define postoperative complications similar to previous population-based studies examining the comparative effectiveness of minimally invasive radical prostatectomy (MIRP) versus ORP [9,10]. Postoperative complications were assigned to the following categories: cardiac, respiratory, genitourinary, wound, vascular, and miscellaneous medical or surgical related complications. To address the heterogeneity in using laparoscopic-specific procedure codes to accurately capture RARP, as done in previous studies [8,9], we elected to use the AHA survey variable regarding presence of a robot surgical system at each hospital to determine type of RP. All patients treated at hospitals with robotic surgery were assigned to RARP cases, while those treated at hospitals without robotic surgery were designated as ORP cases, based on previous studies suggesting strong penetration of RARP by presence of robotic surgery [13,14,24] Statistical analysis The primary outcome of this study was total hospitalization costs, which were estimated from the NIS cost-to-charge ratio and then adjusted to 2008 US dollars using the Consumer Price Index for major expenditures [25,26]. Bivariate associations of patient and hospital variables with ORP and RARP were tested by the Pearson chi-square test. Differences in median total hospitalization costs and LOS were tested by the Mann-Whitney rank-sum test. We then fit generalized estimating equation (GEE) models to assess whether RARP and ORP were associated with higher costs, adjusting for patient and hospital covariates and clustering of patients to the hospital level. To account for the skewed distribution of costs, we specified a gamma distribution and log link in the GEE models [27]. We also performed a sensitivity analysis among a subset of patients undergoing RP from October 2008 to December 2008 to test the validity of our assumption regarding hospital presence of robotic surgery and receipt of RARP. With an ICD-9 code (17.4x) specific for robotic surgery introduced in October 2008, a primary diagnostic code for PCa and concomitant procedure codes for RP and robotic surgery identified RARP cases. Patients without a robotic-surgery procedure code were considered ORP cases in this subset of patients. Similar multivariable analyses were used to identify patient and hospital covariates associated with hospitalization cost. A two-sided p value 0.05 was used to determine statistical significance. Stata MP v.11.0 (StataCorp, College Station, TX, USA) was used to perform all statistical analyses. 3. Results From the NIS and AHA merged data, we identified patients who underwent RP for PCa at 605 hospitals from 2006 to The mean age was yr (standard deviation: 7.13). In comparison to ORP, patients undergoing RARP were, in general, more likely to be younger, white, and healthier, with a lower Elixhauser comorbidity index (Table 1). Furthermore, receipt of RARP was more likely among patients who were primarily insured with private health insurance (79.8% vs 74.8%; p < 0.001), resided in the highest-median-income area (41.8% vs 31.6%; p < 0.001), or treated at hospitals performing a high volume of RPs. Overall, median LOS and total hospitalization costs in our analytic cohort were 2 d (interquartile range [IQR]: 1 3 d) and $9933

3 EUROPEAN UROLOGY 64 (2013) Table 1 Patient and hospital characteristics (N = ) Feature ORP (n = 9413) RARP (n = ) p value Age, yr <0.001 < (16.9) 4006 (19.6) (47.8) 9793 (48.0) (23.7) 4386 (21.5) (9.6) 1863 (9.1) (2.0) 376 (1.8) Race <0.001 White 5213 (55.4) (62.2) Black 654 (6.9) 1591 (7.8) Hispanic 447 (4.8) 846 (4.1) Other 284 (3.0) 757 (3.7) Missing 2815 (29.9) 4528 (22.2) Elixhauser comorbidity index < (74.9) (79.8) (23.2) 3905 (19.1) (1.9) 224 (1.1) Primary insurance <0.001 Private 5970 (63.4) (67.6) Medicare 2856 (30.3) 5620 (27.5) Medicaid 185 (2.0) 348 (1.7) Other 402 (4.3) 646 (3.2) Annual household income, quartile < (lowest quartile) 1493 (15.9) 2754 (13.5) (24.0) 4138 (20.2) (28.6) 4997 (24.5) (31.5) 8535 (41.8) Hospital teaching status <0.001 Nonteaching 4954 (52.6) 5175 (25.2) Teaching 4459 (47.4) (74.7) Hospital location <0.001 Rural 936 (9.9) 473 (2.3) Urban 8477 (90.1) (97.7) Hospital region <0.001 Northeast 1621 (17.2) 6169 (30.2) Midwest 2148 (22.8) 3420 (16.8) South 2028 (21.6) 5337 (26.1) West 3616 (38.4) 5498 (26.9) RP volume, quartile < (lowest) 5237 (55.6) 1931 (9.5) (30.2) 4769 (23.3) (9.7) 6686 (32.7) (4.5) 7038 (34.5) ORP = open radical prostatectomy; RARP = robot-assisted radical prostatectomy; RP = radical prostatectomy. Table 2 Complications, length of stay, and hospitalization costs for patients undergoing open radical prostatectomy (RP) or robotassisted RP (N = ) Feature ORP (n = 9413) RARP (n = ) p value Complications Any 1060 (11.3) 1670 (8.2) <0.001 Medical 840 (8.9) 1360 (6.7) <0.001 Surgical 290 (3.1) 440 (2.2) <0.001 Median (IQR) Median (IQR) Length of stay 2.0 ( ) 1.0 ( ) <0.001 Median (IQR) Median (IQR) Hospitalization cost a 8862 ( ) ( ) <0.001 ORP = open radical prostatectomy; RARP = robot-assisted radical prostatectomy; IQR = interquartile range. a Hospitalization costs adjusted to 2008 US dollars. (IQR: $7657 $12 959), respectively. Approximately 9% (n = 2730) of patients undergoing RP experienced one or more complications. When compared to ORP, as shown in Table 2, patients undergoing RARP were less likely to have medical (6.7% vs 8.9%; p < 0.001) or surgical complications (2.2% vs 3.1%; p < 0.001), or presence of one or more complications overall (8.2% vs 11.3%; p < 0.001). Similarly, RARP was also associated with shorter median LOS and higher hospitalization costs (both p < 0.001). Although most patient covariates in our analysis showed minimal effect on hospitalization costs, multivariable analysis revealed significant associations for patient age, Elixhauser comorbidity, and primary health insurance (Table 3). For example, when compared with private health insurance, Medicare demonstrated significantly lower total hospitalization costs ( p = 0.01). Being treated at urban hospitals and undergoing ORP both showed a significant

4 14 EUROPEAN UROLOGY 64 (2013) Table 3 Multivariable analysis of hospitalization costs by patient and hospital characteristics from 2006 to 2008 Feature (reference) Coefficient (95% CI) p value Age, yr (<55) ( 0.006, 0.019) (0.013, 0.051) (0.015, 0.062) (0.004, 0.081) Race (White) Black (0.027, 0.067) <0.001 Hispanic ( 0.034, 0.018) 0.54 Other ( 0.032, 0.021) 0.70 Missing ( 0.039, 0.008) 0.18 Elixhauser comorbidity index (0 1) (0.069, 0.092) < (0.193, 0.274) <0.001 Primary insurance (Private) Medicare ( 0.038, 0.005) 0.01 Medicaid (0.002, 0.074) 0.04 Other ( 0.002, 0.049) 0.08 Annual household income (1 = lowest quartile) ( 0.018, 0.015) ( 0.019, 0.014) ( 0.028, 0.004) 0.17 Year (2006) ( 0.027, 0.008) ( 0.002, 0.034) 0.07 Hospital teaching status (nonteaching) Teaching ( 0.065, 0.041) 0.67 Hospital location (rural) Urban ( 0.241, 0.095) <0.001 Surgical volume (1 = lowest quartile) ( 0.242, 0.094) < ( 0.212, 0.001) ( 0.301, 0.026) 0.10 Hospital region (Northeast) Midwest (0.008, 0.158) 0.02 South ( 0.103, 0.043) 0.42 West (0.162, 0.303) <0.001 RARP (ORP) (0.194, 0.284) <0.001 CI = confidence interval; RARP = robot-assisted radical prostatectomy; ORP = open radical prostatectomy. relationship with lower costs compared to rural hospitals and RARP, respectively. More specifically, as shown in Table 4, adjusted costs were significantly higher for RARP compared to ORP ($ vs $9390; p < 0.001). Patients Table 5 Adjusted total hospitalization costs for open radical prostatectomy (RP) or robot-assisted RP and by primary health insurance, October 2008 to December 2008 a,b Feature Adjusted costs 95% CI ORP RARP Health insurance Private Medicare Medicaid CI = confidence interval; ORP = open radical prostatectomy; RARP = robotassisted radical prostatectomy. a Hospitalization costs adjusted to 2008 US dollars. b Total hospitalization costs determined for generalized estimating equation adjusted for patient (age, race, Elixhauser comorbidity index, primary health insurance, median income by zip code, year of surgery) and hospital (teaching status, location, region, and annual case volume) covariates. who were privately insured also had higher adjusted costs ($11 160) compared to those patients insured by Medicare ($10 919). Furthermore, patients who were privately insured and undergoing RARP had substantially higher adjusted costs compared with those undergoing ORP ($ vs $9436; p < 0.001). In addition, presence of any complications compared to absence of any complications also yielded higher adjusted costs ($ vs $10 973; p < 0.001) from 2006 to 2008, with similarly higher costs observed for patients experiencing medical ($12 058) and surgical ($12 477) complications when included on multivariable analysis. We also performed a sensitivity analysis among a subset of patients treated during the last quarter of Among the 2728 patients treated with RP during this time period, 1463 (53.6%) and 1265 (46.4%) underwent RARP and ORP, respectively. RARP was also similarly associated with lower median LOS (1 d vs 2 d; p < 0.001) and a lower proportion of patients experiencing any complications (7.4% vs 9.6%; p = 0.04), but also with higher median hospitalization costs ($ vs $9763; p = 0.006). In the sensitivity analysis (Table 5), RARP also correlated with higher adjusted costs compared to ORP ($ vs $9390; p < 0.001). Table 4 Adjusted total hospitalization costs for open radical prostatectomy (RP) and robot-assisted RP and by primary health insurance from 2006 to 2008 a,b Feature Adjusted cost 95% CI ORP RARP Health insurance Private Medicare Medicaid CI = confidence interval; ORP = open radical prostatectomy; RARP = robotassisted radical prostatectomy. a Hospitalization costs adjusted to 2008 US dollars. b Total hospitalization costs determined for generalized estimating equation adjusted for patient (age, race, Elixhauser comorbidity index, primary health insurance, median income by zip code, year of surgery) and hospital (teaching status, location, region, and annual case volume) covariates. 4. Discussion A central finding of this study is that when compared to ORP, RARP is associated with higher total hospitalization costs despite having lower LOS and postoperative complications. Previous studies have reported significant variations in the incremental costs attributable to robotic surgery for RP. For example, Nguyen et al. recently reported that costs for MIRP gradually decreased by 25% from 2002 to 2005 and the differential between MIRP and ORP was, in fact, only $293 among Medicare beneficiaries [8]. Lowrance et al. also found that MIRP cost was only modestly higher at $751 for total Medicare expenditures for 1 yr from of all surgical and medical care related to PCa treatment [28]. However, other retrospective institutional studies described a larger differential ranging from $723 to $1726 per case for RARP [14 16]. More recently, several studies using the NIS from the last

5 EUROPEAN UROLOGY 64 (2013) quarter of 2008 similarly demonstrated that RARP has higher hospitalization costs [18,19]. Yu et al. used propensity score matching to compare robotic, laparoscopic, and open prostatectomy, and demonstrated higher adjusted median costs of approximately $1100 for RARP compared to ORP [18]. Our study further supports that compared to ORP, RARP is associated with higher median and adjusted difference in total costs from hospitalization of $1547 and $2542, respectively. However, there has been a wide variation reported in the health care costs attributable to robotic surgery. For example, previous population-based studies using SEER-Medicare data may have underestimated the cost attributable to robotic surgery in so far as that CMS has not distinguished a difference in reimbursement for RARP, MIRP, or ORP [8,28]. Indeed, Lotan et al. recently reported a detailed economic analysis from a single institution and noted significant variation in reimbursement by type of health insurance, with Medicare having the lowest reimbursement [14]. In our study, we also observed that Medicare was associated with lower total hospitalization costs, which may account for the smaller incremental cost differences observed in SEER-Medicare studies. We also addressed the possible heterogeneity of MIRP by using a different methodology for case ascertainment of RARP. Few studies have also accounted for other key determinants of hospitalization costs for RARP, in particular LOS and postoperative complications. It is possible that the higher costs for RARP shown in previous studies may be confounded by these independent clinical variables, especially since most of these studies occurred during the early adoption of robotic surgery and may be biased by the learning curve for RARP [9]. Moreover, it is well recognized that LOS influences hospitalization costs [5]. Supporting this, Lotan et al. documented from retrospective institutional data that LOS was associated with higher hospitalization costs [15]. Although Trinh et al, using propensity score matching of the NIS data from 2008 to 2009, recently demonstrated that RARP was associated with lower rates of blood transfusion, LOS, and postoperative complications, the relationship of perioperative outcomes and robotic surgery with costs were not examined [10]. We also found that RARP was associated with lower LOS and overall medical or surgical complications, although relative differences in perioperative outcomes were not our primary end point and it is arguable whether these observed differences are not confounded by selection bias by the patient, surgeon, or hospital characteristics. Nonetheless, RARP is associated with a higher incremental cost on multivariable analysis and this difference in higher differential costs was observed whether LOS and complications were either included or excluded on multivariable regression. Therefore, one plausible reason that may explain the higher hospitalization costs for RARP compared with ORP is that hospitals may be billing more to recoup costs from the upfront capital investment to purchase and annual maintenance of the robot. There are several limitations in our study. First, our methodology to estimate hospitalization costs may be biased by the assumption that all patients treated at a hospital with robotic surgery received RARP. However, this assumption likely minimizes the cost difference between the two surgical approaches for RP. More importantly, our sensitivity analysis from the last quarter of 2008, when a procedure-specific code for robotic surgery was made available, supports our primary finding. As a result, a possible inference is that the presence of robotic surgery at a hospital led to higher hospitalization costs irrespective of the type of RP performed. Second, our results may be limited in that our cost estimates are only as accurate as the cost-tocharge ratio provided in the NIS. Greater transparency from multi-institutional data regarding direct costs of robotic surgery and the reimbursement received, in particular for private health insurance, may resolve this controversy and elucidate the magnitude in the difference of actual health care costs with respect to RARP and ORP. Moreover, the costs estimates from the NIS fail to directly capture other areas responsible for higher health care costs, such as the acquisition and maintenance of robotic surgery. Furthermore, our study relied on the NIS in using the cost-to-charge ratio as the means to estimate the hospitalization costs. We acknowledge that our primary outcome relies on estimates of the hospitalization costs for RP from the NIS. Third, the merged data from NIS and AHA do not provide identifying information about the surgeon or tumor stage and grade. Therefore, we were unable to assess whether surgeon volume or tumor characteristics may have modified the costs attributable to robotic surgery. Fourth, any inferences about the higher hospitalization costs associated with robotic surgery are limited to patients, urologic surgeons, and policymakers in the United States. There are limited claims data available from Europe to fully evaluate this policy question, although a previous study suggests significant variation across European countries in the health care costs for PCa [29]. Last, the cost differential may be explained in part by selection bias in choosing ORP in more complicated patients, such as those who had prior abdominal surgery, and this is not captured in claims data. Nonetheless, our results have important policy implications regarding CER to best inform patients, physicians, and key stakeholders with respect to treatment decisions for better patient-centered outcomes and cost-effective medical care. Although observational studies have suggested potential benefits of RARP [8,9,11], it is of concern that there have not been any randomized trials of ORP versus RARP. Additionally, acquisition of robotic surgery may further add incentive to perform RP, in part, to cover the large, upfront, capital investment needed for the robot, annual maintenance fees, and equipment costs [12]. Furthermore, due to the absence of level 1 evidence showing the relative merits of RARP and previous studies suggesting that the rapid adoption may be due hospitals and physicians gaining market share [22,30], ongoing study is warranted. 5. Conclusions We observed that, in the United States, RARP costs approximately $2500 more per case on average in total hospitalization costs compared with ORP. These results have important implications regarding the rapid adoption

6 16 EUROPEAN UROLOGY 64 (2013) of RARP in the face of higher costs and greater emphasis on CER to demonstrate improved outcomes and health care value for patients and urologists. Author contributions: Simon P. Kim had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Kim, Shah, Thompson. Acquisition of data: Shippee, Han. Analysis and interpretation of data: Shah, Shippee. Drafting of the manuscript: Kim, Shah, Thompson. Critical revision of the manuscript for important intellectual content: Boorjian, Smaldone, Frank, Gettman, Tollefson. Statistical analysis: Shah, Shippee. Obtaining funding: Kim. Administrative, technical, or material support: Han. Supervision: Shah. Other (specify): None. Financial disclosures: Simon P. Kim certifies that all conflicts of interest, including specific financial interests and relationships and affiliations relevant to the subject matter or materials discussed in the manuscript (eg, employment/affiliation, grants or funding, consultancies, honoraria, stock ownership or options, expert testimony, royalties, or patents filed, received, or pending), are the following: None. Funding/Support and role of the sponsor: Funding for this study was received from the Healthcare Delivery and Research Scholars Program, Mayo Clinic. References [1] Martin AB, Lassman D, Washington B, Catlin A. Growth in US health spending remained slow in 2010; health share of gross domestic product was unchanged from Health Aff 2012;31: [2] Garber AM, Sox HC. The role of costs in comparative effectiveness research. Health Aff 2010;29: [3] Miller DC, Gust C, Dimick JB, Birkmeyer N, Skinner J, Birkmeyer JD. 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