Barnett, Jason C. MD; Judd, John P. MD; Wu, Jennifer M. MD; Scales, Charles D. Jr MD; Myers, Evan R. MD; Havrilesky, Laura J. MD
Endometrial cancer is the most common gynecologic malignancy in the United States with approximately 40,000 new cases diagnosed annually.1 Surgery is both the primary treatment for endometrial cancer and the means for comprehensive staging as recommended by the International Federation of Gynecology and Obstetrics. In the last decade, several studies, including the large randomized controlled LAP2 trial sponsored by the Gynecology Oncology Group, have demonstrated comparable surgical outcomes between laparoscopic and open (laparotomy) surgical approaches.2–7 Robotic-assisted laparoscopic surgery has recently gained popularity as an alternative surgical approach to the treatment of endometrial cancer and early studies show that it is a promising technique with similar efficacy to laparoscopy.8–11
Because most patients with endometrial cancer present at an early stage when surgery is often curative, the costs related to surgery are a large contributor to the economic burden of treatment. Because surgical outcomes appear to be similar between laparoscopic (including robotic) and open surgical techniques, the cost of treatment should also be relevant to the chosen surgical approach, especially in a climate in which cost-conscious medical care is becoming more important. To better inform this discussion, we performed a cost modeling analysis comparing laparoscopic, robotic, and open abdominal hysterectomy for the treatment of endometrial cancer from both a societal and hospital perspective.
MATERIALS AND METHODS
A decision model was constructed using commercially available software (TreeAge Inc, Williamstown, MA) to estimate and compare the costs (in 2008 U.S. dollars) of laparoscopic, robotic-assisted, and open approaches for the treatment of endometrial cancer. The software was used to construct a simple decision model (Fig. 1) that calculated an average cost for each strategy by multiplying the costs associated with each clinical scenario by the probability of occurrence of that scenario. Clinical probabilities were derived from the published literature; the study was exempt from Institutional Review Board review.
Modeling was performed from three different perspectives: 1) the societal perspective model included costs associated with the surgery, acquisition and maintenance of the robot, hospitalization, and lost wages and caregiver costs; 2) the hospital perspective plus robot costs model excluded lost wages and caregiver costs but included all of the other costs described for the societal perspective model, including the costs associated with purchasing and maintaining the robot; and 3) the hospital perspective without robot costs model was identical to the hospital perspective plus robot costs model except that it assumed prior hospital ownership of the robot and excluded this from the model.
Key assumptions of the model were as follows: 1) we assumed that each surgical approach resulted in equivalent cancer-related outcomes; 2) we assumed that hysterectomy, pelvic, and selective aortic lymphadenectomy was performed using each approach; and 3) we assumed that only rates of conversion of minimally invasive approaches to laparotomy and rates of blood transfusion should be incorporated into cost calculations; the rarity of other potential events with cost implications (eg, thromboembolism, intraoperative injuries) precluded their inclusion. The risk of blood transfusion was incorporated into each cohort with each transfusion volume assumed to be two units of packed red blood cells.
Parameter estimates were derived through review of the medical literature and obtained for the following: operative time, risk of conversion (for laparoscopic and robotic hysterectomy), risk of transfusion, length of hospital stay, and return to normal daily activity after surgery (societal perspective model). A PubMed search was performed in November 2009 using the key words “endometrial cancer” combined with “laparoscopic,” “abdominal,” “robotic,” or “robotic-assisted.” Randomized controlled trial data were used when available. Baseline estimates and reasonable clinical ranges of each parameter for sensitivity analysis were obtained from prior prospective and retrospective studies and are listed in Table 1.
Costs were derived in 2008 U.S. dollars using an itemized costing approach (Table 2) and incorporated preoperative, intraoperative, and postoperative components. Whenever possible, the amount paid by the author's hospital to procure each item was obtained from the hospital accounting department and considered to be its cost. In cases in which only charges to the patient were available, like in the charges for operating room time, a multiplier of 0.6 was applied to the charge to approximate costs (the cost-to-charge ratio).12–14 For specific procedures such as surgeons' and anesthesiologists' fees, Medicare reimbursement15 for specific Current Procedural Terminology codes was used to approximate costs.
Preoperative costs were derived based on time spent in the preoperative holding area. Intraoperative costs included cost per minute of operative time, fixed operating room and anesthesia setup charges specific to the surgical approach, anesthesia per-minute fees, and surgeon and anesthesia physician professional fees (Table 2 [and the Appendix, available online at http://links.lww.com/AOG/A192] for itemization). Physician reimbursement for each procedure was derived from current national Medicare reimbursement rates: Current Procedural Terminology code 00840 for anesthesia (in which reimbursement is linked to procedure time), surgeon codes 58571 and 38572 for robotic-assisted and laparoscopic approaches, and code 58200 for an open abdominal approach (supplementary data).15 Costs of disposable equipment related to each procedure were incorporated, including drapes, gowns, gloves, single-use instruments, sutures, Foley catheter, electrocautery device, scalpel blades, uterine manipulators, and laparoscopic trocars (Table 2 [and the Appendix, available online at http://links.lww.com/AOG/A192] for itemization). For the robotic-assisted approach, the cost of each reusable robotic instrument was evenly distributed across 10 robotic cases based on 10 lives available for each robotic instrument before it must be replaced. Costs for reusable instruments found in standard laparoscopy and laparotomy sets were not included in the model but were included in the sensitivity analysis.
To determine the cost of conversion to laparotomy, we assumed that conversion from robotic or laparoscopic to open hysterectomy would incur the full surgical cost of the initial procedure as well as the cost of the additional operative time required for the conversion. An assumption was made that the additional operative time necessary for conversion would be 30 minutes, and this estimate was varied in the sensitivity analysis.
To account for postoperative care, costs were included for the postanesthesia care unit, hospital room and board, pharmacy, and laboratory tests for the duration of hospital stay. Laboratory test costs, including a complete blood count and basic metabolic panel, were assumed for the initial postoperative day. Pharmacy costs were individualized to the procedure: robotic and laparoscopic hysterectomy included only oral pain medication every 6 hours, whereas open hysterectomy included one 30-mg vial of intravenous morphine through patient-controlled analgesia for the initial postoperative day followed by oral pain medication every 6 hours until discharge. Pharmacy costs additionally included a daily stool softener and assumed one dose each of intravenous and oral antiemetics (odansetron and promethazine). Postoperative intravenous fluid estimates were identical among the three approaches at 1 L for the initial postoperative evening. Estimates for intravenous pharmacy costs were obtained from the Medicare Part B maximum allowable charge, whereas oral medication charges were derived from the lowest advertised price on www.drugstore.com. The costs for hospital room and board as well as transfusion and packed red blood cell unit cost were obtained from the hospital accounting department at the authors' institution.
For the societal perspective and hospital perspective plus robot costs models, the cost of the purchase and maintenance of the daVinci Robotic Surgical System were based on the daVinci S HD system (Intuitive Surgical, Inc, Sunnyvale, CA) and obtained from Intuitive Surgical. Mean purchase price was $1.65 million with an annual maintenance cost of $149,000 per year for years 2–7. The model factored the initial cost and assumed maintenance over a 7-year lifespan. A total purchase and maintenance cost of $2,544,000 was amortized over 7 years at an interest rate of 5% and distributed to each case performed. The baseline estimate for the number of cases per month was based on a hypothetical ideal single robot target use rate of 27 cases per month (Intuitive Surgical, Inc, personal communication), and this was varied from five to 60 cases in the sensitivity analysis.
In the societal perspective model, lost wages and caregiver estimates were included. These data were derived using Bureau of Labor Statistics and average return to normal daily activity found in the literature for each surgical approach (Table 1). Based on the median weekly female wage figure for women aged 16 years and older, $638 per week was used for lost wages with an employment rate of 62.2% (U.S Bureau of Labor Statistics; www.bls.gov). A caregiver was assumed to be present during 50% of the recovery time with the same weekly wage estimates.
One-way sensitivity analyses were used to assess the effects of varying each clinical parameter over ranges reported in the literature (Table 1). Costs were generally varied between 50% and 200% of the original estimate (Table 2); disposable equipment costs were varied over wider ranges for exploratory purposes. Key parameters varied for sensitivity analysis included length of hospital stay, operative time, rate of conversion (laparoscopic and robotic approaches), effect of conversion to laparotomy on total operative time (varied from −30 to 90 minutes), transfusion rate, cost of disposable equipment, total number of robotic cases performed monthly (varied from five to 60 cases), the amount of time until return to normal daily activity (societal perspective model), weekly lost wages of patient and caregiver (societal perspective model; varied from $500 to $1,000/week), and the cost-to-charge ratio (varied from 0.5 to 0.7).
In the societal perspective model, in the base case, laparoscopy was the least costly approach with an average cost of $10,128 per case compared with robotic ($11,476) and open hysterectomy ($12,847) (Table 3). This indicates that laparoscopy was associated with a cost savings of $1,347 over robotic hysterectomy and $2,719 over open hysterectomy.
The societal perspective model was sensitive to the cost of disposable robotic equipment and the total recovery time from robotic surgery (Fig. 2). When the cost of robotic disposable equipment was decreased from the baseline estimate of $2,394 to $1,046 per case or less, robotic hysterectomy became the least costly approach. Alternatively, if return to normal daily activity was less than 12.1 days (baseline estimate 24.1 days) after robotic surgery, robotic hysterectomy also became the least costly approach. Scenarios in which robotic surgery become the most expensive approach were: 1) return to normal daily activity after robotic hysterectomy was longer than 37 days; or 2) fewer than 13 total robotic cases were performed per month (baseline estimate 27). The societal perspective model was relatively insensitive to the addition of initial acquisition costs for laparoscopic equipment (monitors, CO2 insufflator, light source, etc) with no change in cost rankings. Variation of the following parameters over their reported ranges resulted in no change in the relative cost rankings of each approach: length of hospital stay after each approach, variations in lost wages or caregiver costs per week, the cost-to-charge ratio, operative time for each approach, rate of conversion to laparotomy for laparoscopic or robotic approaches, effect of conversion to laparotomy on total operative time, or transfusion rate for each approach.
In the hospital perspective plus robot model, in the base case, laparoscopy was the least costly surgical approach at $6,581 per case compared with open ($7,009) and robotic hysterectomy ($8,770) (Table 3). Laparoscopy was cost-saving by $428 over open hysterectomy and $2,189 over robotic hysterectomy in this model.
In sensitivity analysis for the hospital perspective plus robot costs model (Fig. 3), reducing the cost of robotic disposable equipment to $625 or less resulted in a lower cost for robotic compared with open hysterectomy. Scenarios in which open hysterectomy became the least expensive approach were: 1) length of stay after open surgery was less than 3.6 days (baseline estimate 4.4 days); 2) length of stay after laparoscopy was longer than 2 days (baseline estimate 1.2 days); 3) laparoscopic hysterectomy operative time was longer than 246 minutes (baseline 213 minutes); and 4) open hysterectomy operative time was shorter than 113 minutes (baseline 147 minutes). The hospital perspective plus robot costs model was relatively insensitive with no change in base case cost rankings to variations in the number of robotic cases performed monthly, the cost-to-charge ratio for each approach, rate of conversion to laparotomy for laparoscopic and robotic approaches, effect of conversion to laparotomy on total operative time, or transfusion rate for each approach.
In the hospital perspective without robot costs model, in the base case, laparoscopic hysterectomy was the least costly surgical approach ($6,581) compared with open ($7,009) and robotic hysterectomy ($7,478) (Table 3) with a cost savings for laparoscopic over open and robotic hysterectomy of $428 and $897, respectively.
In sensitivity analyses for the hospital perspective without robot costs model (Fig. 4), when the cost of robotic disposable equipment (baseline $2,394) was reduced to $1,885, robotic became less expensive than open hysterectomy and when reduced to less than $1,496, robotic hysterectomy became the least expensive approach. Scenarios in which open hysterectomy became the least costly approach were: 1) length of stay after laparoscopic hysterectomy was longer than 2 days (baseline estimate 1.2 days); 2) length of stay after open hysterectomy was less than 3.6 days (baseline estimate 4.4 days); 3) laparoscopic hysterectomy operating room time was longer than 247 minutes (baseline 213 minutes); and 4) open hysterectomy operative time was shorter than 113 minutes (baseline 147 minutes). Robotic became less costly than open hysterectomy if length of stay after open hysterectomy was longer than 5.3 days (baseline estimate 4.4 days). The hospital perspective without robot costs model was relatively insensitive with no change in base case cost rankings to variations in the rate of conversion to laparotomy for laparoscopic or robotic approaches, effect of conversion to laparotomy on total operative time, and transfusion rate for each approach.
Minimally invasive surgical techniques are increasingly prevalent in the treatment of endometrial cancer. Several studies, including the Gynecologic Oncology Group LAP2 randomized controlled trial, have built support for laparoscopic surgical approaches as an equivalent if not improved surgical approach with significantly lower moderate to severe postoperative complications when compared with laparotomy.2 From an economic perspective, our results lend fiscal credence to these findings, because laparoscopy is the least costly approach in all three of the models used in our study. The shorter hospital length of stay and overall recovery time associated with minimally invasive approaches is reflected in the lower cost of both robotic and laparoscopic approaches compared with an open approach when examined from a societal perspective (societal perspective model).
The societal perspective model takes into account the costs related to lost wages experienced by the patient and the patient's caregiver during the recovery time after surgery. Primary benefits of minimally invasive surgery include decreased hospital stay, shorter recovery, and quicker return to normal daily activity after surgery.2–11,16 Although it is difficult to quantify the true impact of surgical recovery on societal costs, we have incorporated lost wages and caregiver costs using Bureau of Labor Statistics data. Although the costs associated with lost wages may not intuitively seem to affect the average woman with endometrial cancer, according to Bureau of Labor Statistics' figures, 62.1% of women aged 55–64 years are employed (median age for endometrial cancer is 60 years old) with a weekly median salary of $711 per week. Because women with endometrial cancer have a broad age range, to simplify, we used statistics representing the median weekly wage for all working women in the United States (women aged 16 years and older). Our figures are comparable to or lower than other estimates found in the literature for lost productivity costs so that minimally invasive techniques may provide even more societal cost savings than we included in our model.16 The current model does not account for costs to employers for lost work time by the patient or caregiver, which, if included, would further favor a minimally invasive approach. Even using modest cost estimates, minimally invasive surgical techniques were cost-saving when viewed from a societal perspective.
In the hospital perspective models, costs related to lost wages and caregiver expenses were removed. When the societal cost of recovery time is not taken into account, all three strategies are closer to each other in cost such that the relative cost rankings are more subject to change over the parameter ranges explored for sensitivity analysis. In particular, open hysterectomy became the least expensive approach when hospital stay and operative time using this approach were at the favorable end of their ranges. Because one criticism of robotic surgery is the perceived high cost associated with acquisition of the robot, these costs were retained in the hospital perspective with robot costs model. Not surprisingly, robotic surgery was the most expensive approach, costing $2,189 more than laparoscopy and $428 more than laparotomy per case. However, if robotic disposable equipment was kept less than $625 per case, robotic surgery became less expensive than laparotomy. Because laparoscopy was the least expensive surgical approach in all three models, one might argue that laparoscopy maintains the benefits of minimally invasive surgery without the increased costs associated with the robot. Nonetheless, robotic-assisted laparoscopy has significant benefits, including enhanced ergonomics, greater surgeon comfort, greater ease of performing more complicated surgeries such as radical hysterectomy as a result of the enhanced ability of the robot to mimic “wristed” motion, and potentially improved surgeon longevity17—all of which are intangibles that are not included in our model. Additionally, in the morbidly obese patient, robotic surgery may enable more patients to be comprehensively staged using a minimally invasive technique when compared with laparoscopy.18
Many hospitals already own one or more robotic units and some view the initial cost of the robot as a one-time investment. In the hospital perspective without robot costs model, we excluded the initial purchase cost of the robot to reflect this view. Costs among the three approaches were much more comparable from this perspective, and the primary determinant of cost in this model was related to the costs of disposable equipment. In fact, when the cost of robotic disposables was decreased to $1,496 per case, the robotic approach became the least expensive. Interestingly, this is similar to initial studies comparing the costs between laparoscopic-assisted vaginal hysterectomy and abdominal hysterectomy for benign disease, which showed laparoscopic-assisted vaginal hysterectomy to be more expensive than open surgery, primarily because of costs associated with the use of disposable equipment.19 As hospitals that already own a robot seek to maximize the cost efficiency of their purchase, minimizing costs associated with disposable equipment appears to be paramount.
In a prior cost analysis of surgical approaches to the treatment of endometrial cancer, Bell et al16 compared the outcomes and expenses associated with 40 robotic, 30 laparoscopic, and 40 open surgeries. This study supported the cost savings associated with minimally invasive approaches, because the average costs of laparoscopic and robotic surgery were lower than the cost of laparotomy. Hospital length of stay was the most influential determinant of cost in this prior study. Bell et al performed detailed reporting of the average hospital costs associated with each approach and the incorporation of both direct and indirect costs. Because this prior study used lost wages and lost household productivity estimates, it is most similar to the societal perspective model in our present study and supports our findings that laparoscopic and robotic approaches are the least expensive approaches when viewed from a societal perspective. Although the prior study found the primary driving force behind cost to be hospital length of stay, our model additionally demonstrated the significant contribution of disposable equipment to the costs of robotic surgery. Our model also allowed us to view cost from several different perspectives as compared with the retrospective analysis performed in this previous report.
There are several limitations to our study. Although modeling provides a means to predict and compare expenses, it is difficult to identically replicate all the costs associated with real-world scenarios. In a large robotic surgery program, a hospital may own several robotic units, allowing for higher numbers of robotic cases per month and shared use of the robot between several different surgical services. Our model used 27 cases per month as the baseline estimate with the assumption that only one robot was owned by the hospital. More than 27 cases per month could potentially be performed if two to three cases were performed daily during a normal business week (40–60 cases per month), but it is unlikely that even the busiest gynecology oncology practice would have this many endometrial cancer cases. In fact, most gynecologic oncologists who perform robotic surgery likely use the robot for more than just endometrial cancer surgery and this was not taken into account in our model. Alternatively, for a hospital expecting a very low robotic case volume (less than 13 cases monthly), the current model indicates that a robotic approach is less economically attractive. Another limitation is that we did not incorporate complication or readmission data in the model. Overall, the individual complication rate is so low that it would be difficult to reliably model these variables, but we acknowledge that a serious complication could add substantial cost to an individual case. Additionally, as reported in the LAP2 trial, there was no difference in intraoperative complication rate between open and laparoscopic surgery (8% compared with 10%, respectively)2; this suggests that costs associated with catastrophic intraoperative complications would unlikely affect the overall cost rankings. However, inclusion of other complications such as wound infections could affect overall costs in the model, especially from a societal perspective. An additional potential limitation is that most of our baseline clinical parameter estimates were determined primarily using published data from one institution.8 We used the largest comparative study that included all three approaches, because this allowed for control of potential confounding variables that may come from differences in institutional practice patterns (ie, operative time, discharge practices). However, these parameters may reflect a publication bias because published results often demonstrate the optimal experience of a surgical team especially proficient in the reported technique and not necessarily exemplify the broad experience of the surgical community. Our sensitivity analyses, however, included a full spectrum of estimates from the literature, including the values published in the multicenter LAP2 trial,2 which strengthens the validity of our analyses.
Robotic surgery will likely grow in popularity. Long-term data on the use of robotic surgery for the treatment of endometrial cancer are not yet available and adverse events or other drawbacks may eventually emerge challenging its appropriateness. If equivalent efficacy is assumed, there are likely intangible benefits not included in our model that may support the use of this approach. Moreover, as the cost of disposable equipment is minimized, robotic surgery approaches laparoscopy in cost savings. With technologic advances and market competition, the price for acquisition and maintenance of a surgical robot may eventually decrease. Likewise, the addition of robotic capability to a hospital's operative armamentarium may result in improved referral rates and higher clinical volume. However, because the use of the robot may affect room turnover time, operating room capacity, personnel costs related to robot setup and disassembly, and potentially lost surgeon “opportunity costs” related to the extra time needed for robotic surgery, future studies need to assess the impact of robot use on overall surgical volumes. Looking for ways to minimize cost, possibly through reduction in the price of disposable equipment or development of strategies to optimize operating room resource use, is important as more patients with endometrial cancer request minimally invasive surgery and many surgeons prefer it. Additionally, future studies evaluating the full breadth of robotic surgery, including contributions of several different surgical subspecialties, will likely better demonstrate the cost utility of robotic surgery.
In summary, this cost model estimates that laparoscopic surgery is the least costly surgical approach from both a hospital and societal perspective when compared with robotic and open surgery. Assuming equivalent efficacy, quantification of the cost associated with different surgical techniques should have a contributing role in determining the optimal surgical approach to endometrial cancer. As robotic surgery becomes more popular in the treatment of endometrial cancer, cost-minimization strategies such as decreasing the costs associated with robotic disposable equipment should improve the economic attractiveness of this approach.
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© 2010 by The American College of Obstetricians and Gynecologists.