A cost analysis of robotic lung resection versus stereotactic radiosurgery

Introduction

Lung resection and stereotactic body radiation therapy (SBRT) are the two most common procedures utilized to treat early-stage lung cancer and oligometastatic diseases within the lung. Minimally invasive lung resection using robotic and video-assisted thoracoscopic surgery (VATS) techniques have been demonstrated to decrease perioperative complications, improve recovery, and lead to decreased pain and length of stay (1,2). Robotic lung resections (RLR) include lobectomy, segmentectomy, and wedge resection; the decision on amount of parenchyma to be resected depends on pathology, location of lesion, pulmonary function, and medical comorbidities. RLRs are preferred for patients who are acceptable operative candidates, whereas SBRT is the preferred treatment for medically inoperable patients (3). Many studies have analyzed these procedures in terms of oncologic success rate and survival, but little is known about the relative costs of these treatment modalities.

Lung resection has generally been demonstrated to offer the most favorable oncologic outcomes when treating early-stage lung cancer, but this can be offset by involving a higher risk of morbidity in comparison to SBRT (4,5). SBRT has proven to be more precise than other forms of radiation therapy and is associated with much improved local control and overall survival rates (6,7). Concerns about higher rates of local recurrence and limited lymph node staging have limited the adoption of SBRT as a primary treatment for patients with low operative risk (8). Studies indicate favorable results for SBRT in the short term. However, when the follow-up range is extended to 5 years, surgical intervention has been shown to offer an 11.5% higher survival rate in comparison to SBRT (9). These reports are further complicated by the likelihood of selection bias affecting the comparison between RLR and SBRT. When this factor is considered, studies report improved survivability with SBRT (10).

The decision for a patient to undergo RLR or SBRT is based on multiple factors such as age, performance status, respiratory function, and comorbidities. Although the optimal treatment choice is often clear, for some patients, deciding between RLR and SBRT may be challenging for both clinician and patient. Cost-benefit analysis does not have a major role in the care of an individual patient but may be valuable for population-wide or system-wide decisions for equivocal cases in a highly resource-constrained setting. The goal of this study is to take the first step in this effort by determining the relative costs of RLR and SBRT. We present this article in accordance with the CHEERS reporting checklist (available at https://ccts.amegroups.com/article/view/10.21037/ccts-23-12/rc).

Methods

Patients and data collection

This study was a retrospective cost-analysis of RLR and SBRT. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the UAB Institutional Review Board for Human Use (IRB-101217008) and individual consent for this retrospective analysis was waived. All patients in the RLR group received a definitive histopathological diagnosis of lung cancer. All patients who received SBRT either had a pre-therapy biopsy that showed lung cancer or received empiric treatment for presumed lung cancer based on imaging findings and clinical suspicion (11). We analyzed consecutive procedures dating from January 2017 to December 2018 using electronic medical record data. A total of 202 patients were analyzed. 103 of those patients were RLRs and 101 were SBRT patients.

Technique: RLR

RLR is performed with a completely portal 4-arm technique that has been previously described (12). The Davinci Xi system (Intuitive; Sunnyvale, CA, USA) with a dual console is used for the operation. The typical instruments used in the operation include Cadiere forceps, curved bipolar dissector, fenestrated bipolar forceps, and tip-up fenestrated grasper. Robotic staple fires (30 mm curved tip and 45 mm standard) are used for dividing vessels, bronchi, and parenchyma in the vast majority of situations during the operation, although occasionally a linear Endo GIA handheld stapler (Medtronic; Minneapolis, MN, USA) is used if necessary. Other major disposable items used during the surgery include an Airseal access port and connecting tubing (Conmed; Largo, FL, USA), a 12 mm Endopath Xcel port for specimen removal (Johnson & Johnson; New Brunswick, NJ, USA), a polytetrafluoroethylene (Gore-Tex) specimen bag, and a 5 mm suction-irrigator device (Stryker; Kalamazoo, MI, USA).

Technique: SBRT

Prior to SBRT, electromagnetic navigational bronchoscopy is performed with the superDimension Navigation System (Medtronic). The Edge EWC Firm Tip 180° locatable guide (Medtronic) is navigated to the target lesion, and two SuperLock nitinol coil fiducial markers (Medtronic) are deployed under fluoroscopic guidance. SBRT was performed on an Edge Radiosurgery System linear accelerator (Varian Medical Systems, Palo Alto, USA) using volumetric-modulated arc therapy (VMAT) to deliver a flattening filter free 10 MV photon beam at 2,400 monitor units (MU)/minute to the target. Prior to treatment, patients were immobilized in the supine position with arms up in a custom molded cradle and underwent CT simulation using Real-position Management (RPM; Varian Medical Systems) for respiratory motion assessment using 4D-CT. Target delineation and treatment planning were performed according to published standards (13,14). Peripheral lesions located >2 cm from the proximal tracheobronchial tree and not adjacent to the chest wall were eligible for 3 fractions (on non-consecutive days) SBRT (most commonly 54 Gy in 3 fractions), while most others received 5 fraction SBRT (most commonly 52.5 Gy in 5 fractions). Standard pre-treatment image guidance consisted of paired orthogonal KV X-rays matched to bony anatomy and fiducials, followed by cone beam CT. Intra-fraction imaging was used to confirm accurate localization of fiducial markers.

Costs defined

Only direct costs were examined in this study. Direct cost can be defined as any expense to the hospital resulting from the performance of the procedure plus other incidental costs within 30 days of the procedure. For RLRs, this category is largely comprised of surgical costs, hospitalization fees, staffing expenses, and any instance of intense care unit (ICU) stay. Direct costs of SBRT included clinical expenses of simulating, planning, and delivery of the radiosurgery. This category also involved the cost of navigational bronchoscopy with fiducial marker placement, which was the standard of care for the performance of lung SBRT at our institution. Cost is determined based on the services and procedures provided during the stay, determined from the charge code level data for each patient. These costs were obtained from UAB Hospital’s cost accounting system which utilizes an activity-based costing methodology with costs allocated to individual charge codes based on RVU’s assigned to each charge code.

Indirect costs were not included in this study. RLR procedures are subject to indirect costs such as surgical robot purchase, maintenance, depreciation, and amortization. Indirect costs of stereotactic radiosurgery (SRS) include the price, maintenance, depreciation, and amortization of the SRS linear accelerator. Clinical follow-up visits, radiologic surveillance, and any other expense that exceeded the 30-day period were not included in the total for either RLR or SBRT. The cost of medical care other than the index procedure and hospitalization within 30 days of the date of the procedure was also not included in this analysis. We decided to exclude these costs, as patients may seek medical care in other settings and locations (cost data not available). In addition, it can be difficult to determine with certainty whether or not these costs are related to the procedure itself.

Statistical analysis

The sub-costs of each procedure were allocated into their respective grouping and added together to provide the total cost. These average component costs’ contribution to the overall direct cost per patient depended on the frequency of the component. These total costs were then divided by the number of patients to calculate the average cost per patient. Interquartile range and median costs have also been evaluated. This was completed for both RLR and SBRT. The averages of these costs were analyzed via Welch’s two-sample t-test at 95% confidence interval (P≤0.05) given the unequal cost variances of costs between the two procedures. This test only involved 79 of the 101 SBRT patients due to limitations of cost details imposed by the timing of fiducial marker placement. This test was also employed to compare average direct costs between robotic lobectomies and sub-lobar resection procedures.

A propensity-matched analysis was used to compare costs between the RLR and SBRT groups. Logistic regression was used to model the likelihood of undergoing robotic surgery, incorporating all preoperative characteristics, including demographics [age, gender, race, body mass index (BMI)], comorbidities [history of hypertension, chronic obstructive pulmonary disease (COPD), coronary artery disease (CAD), congestive heart failure (CHF), stroke, diabetes], clinical tumor size and histology, and disease-related measurements [ZUBROD score, diffusing capacity for carbon monoxide (DLCO), forced expiratory volume in one second (FEV1), and cigarette pack-years]. The calculated propensity scores were then used to match robotic and open surgical cases into pairs if the absolute difference between their scores was <0.05. A case was allowed to be matched multiple times as long as it met the matching criteria. The propensity score-matched cohort included unique cases that had been matched.

Results

Not surprisingly, compared to patients in the RLR group, patients in the SBRT group were older (mean age 70 vs. 65 years, P<0.001), had a more extensive smoking history (never smokers 12% vs. 26%, P=0.01), worse functional status (Zubrod 0 of 7% vs. 30%, P<0.001), worse pulmonary function testing (FEV1 % predicted of 64% vs. 80%, DLCO % predicted of 56% vs. 76%, P<0.001 for both comparisons) and more comorbidities (COPD 58% vs. 27%, P<0.001, CHF 17% vs. 3%, P<0.001, CAD 32% vs. 18%, P=0.02). Patients in the SBRT group were more likely to be male (58% vs. 43%, P=0.003) and have a lower BMI (26.5 vs. 28.5 kg/m², P=0.02), although the latter is not likely clinically significant. Patients in the RLR group had larger sizes of tumor (2.8 vs. 2.4 cm, P=0.03) and fewer T1aN0 cancers (9% vs. 20%, P=0.04), and a higher percentage of adenocarcinomas (59% vs. 48%, P=0.009) than patients in the SBRT group. These discrepancies are summarized in Table 1.

The total direct costs recorded for overall RLR procedures amounted to $1,256,284.82. This value was divided by the total number of RLR patients to yield a direct cost per patient of $12,197. The total direct costs recorded for overall SBRT procedures amounted to $508,187.65. This value was divided by the total number of SBRT cases to yield a direct cost per patient of $8,933. The total direct costs of RLR were 36% greater than that of SRS. RLR was also revealed to have a median cost of $11,133 per patient compared to SBRT’s median cost of $5,290 per patient. Tables 2,3 summarize these findings. The paired-sample t-test indicates a significant difference between the two averages of SBRT and RLR cost (t=4.80, 132 df, P<0.001). Of the evaluated RLRs, 7% of the procedures were segmentectomies, 22% were wedge resections, and 71% were lobectomies. Of RLR costs, lobectomies had an average direct cost of $12,932 while sub-lobar resections displayed an average cost of $9,329. There was also a statistically significant difference found between these two sub-group averages (t=3.33, 58 df, P=0.002).

After propensity matching according to likelihood of undergoing robotic surgery, there were 21 patients in SBRT group and 92 patients in the RLR group. The direct cost of RLR was $11,882, whereas the direct cost of SBRT was $5,194; this was similar to the direct costs in the unmatched groups ($12,197 for RLR vs. $5,032 for SBRT). The unpaired-sample t-test indicates a significant difference between RLR and SBRT cost in the propensity matched groups (t=6.9944, 111 df, P<0.0001).

As seen in Table 4, which documents individual costs, the most significant contributors to SBRT costs are made up almost entirely by radiation oncology ($5,032/patient) and fiducial marker placement ($3,901/patient). The highest component direct costs for RLR patients consisted of surgery ($6,591/patient) and ICU fees ($9,241/patient). While the cost of ICU care was the highest, lab expenses ($1,458/patient) and nursing costs ($1,524/patient) contributed more to overall cost per patient considering only 3% of RLR patients received ICU care. Discrepancies in cost occur when only applied to a smaller subset of patients.

Radiation oncology costs were further broken down: the raw cost contributors were designated to consultation, simulation, and treatment radiation oncological costs as shown in Table 5. As expected, treatment costs ($3,883/patient) were the main contributor to radiation oncology costs, also making it the main contributor to overall SBRT costs. Consultation costs ($1,099/patient) proved to be the second largest expense followed by simulation costs ($59/patient).

In this study, we calculated the average costs of RLR and SBRT procedures. The cost of RLR is 36% higher than SBRT per patient on average. Fiducial marker placement made up 44% of SBRT costs while the other 56% was made up of radiation oncology. The main contributor to RLR costs was surgery expenses, which made up 54% of the costs. Lab and nursing expenses followed in terms of contribution to the overall cost per patient with each making up 12% of the overall cost. ICU care for RLR procedures proves to be a substantial expense ($9,241/patient), however, this was a rare occurrence as only 3% of RLR patients required it. If ICU costs were excluded from this study, the average RLR cost would be $11,928 per patient (as opposed to $12,917). The RLR cost per patient would be 34% greater than that of SRS in this scenario, retaining a significant cost difference. In terms of the ICU patients, one patient experienced a postoperative myocardial infarction, ARDS requiring intubation, and acute renal failure requiring dialysis, necessitating a month-long hospital stay. Another patient experienced postoperative hypotension that required vasopressor usage, resulting in a 3-day ICU stay and a 5-day hospital stay. The final patient was reintubated in the operating room after lobectomy and therefore transferred to the ICU. He was extubated on postoperative day 1 but was reintubated on postoperative day 2. He also underwent toilet bronchoscopy for secretions, started antibiotics for pneumonia, and remained in the ICU for 4 days (7-day hospital stay). Most of the patients who experienced ICU stay in this study underwent lobectomies instead of sub-lobar resections. This is likely one of the main contributors to the average direct cost of lobectomies being 39% greater than that of sub-lobar resections. The other contributors to the additional cost of lobectomy would be increased use of disposables such as staple fires during lobectomy vs sublobar resection and increased operative duration.

Discussion

Our study demonstrates that SBRT is less expensive than RLR as a treatment modality. However, price should not be confused with cost-effectiveness. Cost-effectiveness is a metric that reflects the efficacy of a procedure or operation and requires the investigator to determine the success rate of each modality. Prior studies have shown RLR procedures to be associated with an average 0.25% mortality rate within a 30-day post-operative period, a 0.5% mortality rate in a 90-day period, and a morbidity rate of 9.6% (15). Furthermore, local tumor recurrence following RLR has been reported to be as low as 3% (16). RLR also displays a 5-year survival rate of up to 73%, which is largely dependent on the tumor staging (17). For SBRT, publications indicate a mortality rate of 0% within a 30-day post-procedure period. However, SBRT patient survival decreases to 49% within 2 years post-procedure and further drops to 31% within 5 years (18). Additionally, studies indicate a local tumor recurrence rate of 8.4% for post-SBRT patients (19). The discrepancy of patient age and comorbidity across SBRT versus RLR is likely the primary contributor to the post-procedure survival rates.

Our study highlighted the various components of cost for RLR and SBRT and their relative impact. Our median hospital length of stay after RLR was only 2 days, which already compares quite favorably to the literature (20,21). Recent studies suggest RLR day-1 post operative chest tube removal is safe and growing more frequent with an incidence as high as 93% (22). This trend can result in shorter hospital stays, making RLR post-operative day-1 discharges more feasible (23). Generalizing our cost analysis to other institutions that typically experience a longer length of stay after robotic lung surgery may understate the cost advantages of SBRT. Regardless, decreasing this length of stay further would reduce nursing, lab, respiratory, and pharmacy costs. This is important to note when considering RLR in comparison to other surgical methods. RLR retains the highest direct costs relative to its counterparts. Despite these costs, RLR may be associated with shorter hospital stay and superior lymph node dissection when compared to open or video-assisted lobectomies (24). Hospital day 1 discharge has become increasingly common following lung resection (25). This could be linked to the rapidly increasing rate of RLR implementation and its unique advantages (26). This trend can be expected to continue given RLR usage has increased to 18% of all lobectomies while open lobectomy has dropped down to 26%, VATS remains the most common modality at 54% (27). Currently, we estimate that 20–30% of our patients are discharged on postoperative day one following robotic lobectomy, a proportion that has increased since the time of this study and may further reduce costs associated with RLR. Minimizing the use of laboratory tests could also significantly reduce cost after RLR (28). Although our study did not examine the duration of procedure and/or OR time, increasing the efficiency of the operating room could lead to decreases in both of these parameters and presumably decreased costs as well. In one of our prior studies, we calculated an operative time from the initial marking of ports to the final specimen bagging to be around 80 minutes. This time is increased by 37 minutes in the form of efficient preoperative measures (29). Given that a recent publication reported an optimized robotic lobectomy to cost around $9,912, this translates to OR costs of roughly $85/minute (16). A decrease of 30 minutes per RLR could theoretically lead to a decreased cost of $2,550/case if the above-cited estimate of operating room cost is used. Decreasing the utilization of instruments and staplers could also potentially decrease the cost of RLR (30). Finally, minimizing the occurrence of complications and/or ICU admission with improved patient selection, surgical technique, and/or postoperative care would impact resource utilization and decrease the cost of RLR.

With regards to SBRT cost, radiation oncology charges and the cost associated with fiducial marker placement accounted for 99% of the total cost of SRS. These main SBRT cost contributors give an especially accurate portrayal of procedure costs given their consistent utilization from patient to patient. The RLR model is hindered in this regard as ICU stay, the largest cost contributor, is only observed in 3 patients resulting in moderately skewed RLR costs. One way to mitigate the cost of SBRT could include decreasing the number of fractions delivered to each patient (higher dose for fewer fractions for a similar total dose). At our institution, certain patients are selected for a 3-fraction treatment rather than 5-fraction, depending on the size and location of the tumor. Studies indicate 5 fraction treatments can cost up to €9,234, resulting in a cost of €1,847 per fraction (31). This cost equates to about $2,203 per fraction. With this model, hypothetically, switching from a 5-fraction approach to a three-fraction treatment could save up to $4,406 per patient. Increasing the proportion of patients offered a 3-fraction treatment plan could decrease the overall cost of SBRT. Another way to mitigate the cost of SRS would be to increase selectivity about which patients received fiducial marker placement. Currently, all patients getting SRS receive fiducial marker placement, and tracking of fiducial markers occurs for both gated and non-gated treatments. Upper lobe tumors tend to have less motion than lower lobe tumors; fiducial marker placement may potentially be omitted in these patients if trying to prioritize cost savings. In the future, advances in technology may permit the tracking of the tumor volume itself rather than using fiducial markers.

When only considering costs, other analyses suggest SBRT is the more cost-effective treatment (3,4,8). Although some studies are only applicable to marginally inoperable patients, more recent studies suggest SBRT is more cost-effective even for medically operable patients (32). These findings must be interpreted with caution, as cost comparisons between these procedures are still prone to many unknown discrepancies. SBRT is unlikely to be equivalent in terms of RLR in terms of likelihood of recurrence and overall survival (33). Bijlani et al. report RLR exceeding SBRT in average cost by 25% and recognize it as a cost-effective method to treat early-stage lung cancer (34). Others report RLR as being the most cost-effective surgical method at higher willingness-to-pay thresholds, and that RLR can be further optimized through increased efficiency (35). Cost analysis results for these procedures are reasonably clear when comparing them in a 30-day period. However, this period does not account for follow-up visits or costs associated with tumor recurrence. If one procedure observed a higher success rate than the other, then the overall cost-effectiveness may lie in its favor considering the other procedure’s recurring cost would increase substantially. In the past, RLR procedures have been associated with more positive long-term results while SBRT is designated with an inferior life expectancy (24). This perspective may be skewed, however, when considering SBRT is typically designated to older patient populations who are considered inoperable. This suggests that the patient already has a degree of unrelated comorbidities that indicates the risk of harm from surgery does not outweigh the potential benefits (36). This makes it difficult to differentiate whether the lower quality of life associated with post-treatment SBRT is due to the treatment itself or is instigated by unrelated illnesses. To develop this concept, future studies, whether analyzing cost-effectiveness or clinical outcomes, should target patients who fall in the middle of being clearly operable or completely inoperable.

One major limitation of this study is that it examines only the cost of the procedure itself and does not consider the costs of surveillance, additional procedures or studies, or disease recurrence. In addition, this study does not consider indirect costs, which contribute significantly to the total cost for both RLR and SBRT (cost of robotic platform and radiosurgery platform, respectively). As a single institution study, the costs of RLR and SBRT may not be generalizable to other centers, especially those outside of the United States. Centers with a higher percentage of VATS lung resections, which has been shown to cost 13% less than RLR, likely will have a lower cost differential between minimally invasive lung resection and SBRT than what was revealed in our study (37). From the perspective of SBRT, our institution utilizes fiducial marker placement for nearly all patients, which adds significantly to cost and may not be the standard at other centers. In addition, as Table 1 shows, the characteristics of patients who receive RLR and SBRT differ significantly—namely patients receiving SBRT have worse pulmonary function and more comorbidities than those who receive RLR; therefore, the difference in cost between the techniques described by our study may underestimate what would occur in the real-world if these groups were more similar, as older/sicker patients are more likely to experience complications after surgery and therefore incur additional costs. In addition, the RLR group contained patients undergoing a variety of lung resections, ranging from wedge resection to lobectomy. Recent literature indicates SBRT results in a significantly higher local tumor recurrence rate when compared to wedge resections (38). Other studies further suggest wedge resections boast a higher overall survival rate than SBRT (39). It is important to note, however, that SBRT patients tend to present with a higher incidence of comorbidities, which can directly impact survival rates. Wedge resections and SBRT display similar cause-specific survival outcomes when this discrepancy is accounted for (39,40). We decided to include all types of resections in this study because lung cancer patients may not necessarily be a candidate for wedge resection due to the location and/or size of the tumor. We therefore felt that studying all types of RLR versus SBRT would be a more appropriate comparison than robotic wedge resection only versus SBRT. Finally, survival and patient quality of life were not considered for this study. A meaningful cost-effectiveness analysis would have to consider differences in life expectancy and cancer recurrence rate between patients undergoing RLR versus SBRT. Given that the patients who undergo RLR and SBRT are likely to be qualitatively different, however, this may be a difficult comparison to make. It is important to remember that the decision with regards to choosing RLR vs. SBRT in a particular case is based on medical factors and patient preference, and not cost. Differences in cost between the two modalities have definite implications for health systems and payors, but cost-effectiveness rather than cost alone should be considered a more important metric for these entities.

Conclusions

Our data indicates SBRT has a lower direct cost per patient. It remains unclear, however, if it is the more cost-effective strategy for medically operable patients. Strategies to minimize RLR costs should target the efficiency of robotic involvement and reduce the utilization of ancillary services. Decreasing SBRT cost could focus on a more selective approach to fiducial marker placement. To better understand the relative cost-effectiveness of these treatments, long-term effects, and costs should be considered in the context of a propensity-matched group of patients receiving RLR and SBRT. Cost minimization strategies and studies regarding costs not typically considered are needed to better understand the cost-effectiveness of these procedures.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CHEERS reporting checklist. Available at https://ccts.amegroups.com/article/view/10.21037/ccts-23-12/rc

Data Sharing Statement: Available at https://ccts.amegroups.com/article/view/10.21037/ccts-23-12/dss

Peer Review File: Available at https://ccts.amegroups.com/article/view/10.21037/ccts-23-12/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://ccts.amegroups.com/article/view/10.21037/ccts-23-12/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the UAB Institutional Review Board for Human Use (IRB-101217008) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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