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Page 4 of 10 Nishimura et al. Mini-invasive Surg 2020;4:11 I http://dx.doi.org/10.20517/2574-1225.2019.48

costs, direct costs, and/or indirect costs. Details on operating room (OR) charges and costs were provided
by some studies. Professional fees were included in some studies, but not all. The micro-costing method
[11]
[7]
was used to assess costs in the studies by Kaur et al. and Gondé et al. Relative cost, rather than absolute
[12]
cost, was reported in the study by Park .
Total costs were reported as the sum of indirect and direct costs in the study by Nasir et al. . Direct
[13]
cost was defined as the cost of any items used and services provided in the care of the patient during the
hospitalization. This included all operating room disposable equipment and supplies; staplers; laboratory
tests; imaging studies; pharmacy items and medications; and salaries and benefits of personnel who
delivered care to the patient. Indirect cost was defined as overhead cost and amortization of capital
equipment and supplies and maintenance.

Robotic specific costs were defined and reported by many studies and included direct costs such as
disposable instruments, drapes, and other supplies. Other robotic specific costs provided included amortized
[14]
cost/capital depreciation and maintenance costs. Robot depreciation in the study by Novellis et al. was
estimated from capital cost of 2 million euros plus annual maintenance of 200,000 euros divided by the
[15]
number of procedures per year (400 cases) over eight years. Deen et al. calculated capital depreciation
and service cost of 1200 USA dollars (USD) per case by considering four robots priced at two million USD
[7]
each, performing 2403 procedures in a 22-month period. Gondé et al. calculated capital depreciation by
dividing the sum of the purchase price and maintenance cost by the number of surgical procedures per year
[16]
multiplied by the depreciation period. In the study by Nelson et al. , the depreciation was calculated over
five years. Some studies included these costs in the total hospitalization cost, while others did not. In the
[11]
study by Kaur et al. , these costs were excluded since they were reported to be covered by philanthropic
subsidies and assumed no extra cost to the public health system of Canada. In the population-based study
[9]
by Swanson et al. , the cost that they reported incorporated the cost of the procedure to the hospital, but
not the acquisition and annual maintenance cost of the robot.

In the prospective study by Gondé et al. , total cost was defined by length of stay related costs (clinical
[7]
expense, medical logistics, general logistics, and buildings) and costs independent of length of stay (direct
charges including medical supplies and medico-technical expenses including capital depreciation).
Part of the cost calculations in this study was based on the French National Cost Study database. In
two population-based studies, Subramanian et al. and Paul et al. estimated costs by using total
[1]
[10]
hospitalization charges and applying hospital-specific cost-to-charge ratios. It is unclear how cost was
[8]
derived in the study by Glenn et al. , another population-based study, which had the highest total cost
[14]
(102,057 USD) reported of all studies. In the study by Novellis et al. , estimated cost was reported as
percentage of regional health service reimbursement. This was derived from using actual costs as well as
estimated costs.

Cost comparison of robotic lobectomy to vats and open lobectomy
Six of 16 studies compared the cost of robotic lobectomy to both VATS and open approaches [Table 2] [1,12,14-17] .
Two studies found no significant difference in adjusted costs when comparing robotic approach to either
VATS or open approach for the total hospital stay [16,17] ; however, one of these studies noted that it may
[16]
have been underpowered to detect a difference between groups . Both studies used propensity score
[17]
adjustment by inverse probability of treatment weighting. The study by Kneuertz et al. did not find a
difference in OR costs when comparing robotic to VATS (USD 9912 vs. USD 9491; P = 0.44); however, open
approach had lower operating room costs than robotic (USD 8698 vs. USD 9912; P < 0.01). They observed
[15]
an inverse relationship between OR related costs and postoperative related costs. Deen et al. found that
the overall cost for robotic approach was significantly higher than VATS ($17,011 vs. $13,829; P < 0.001),
but did not find a significant difference when compared to open approach ($17,011 vs. $15,036; P = 0.058).