Laparoscopic versus robotic adrenalectomy for large adrenal tumours (≥6 cm)

Introduction

Background

Minimally invasive adrenalectomy is the standard of care for adrenal surgery, offering significant advantages over open surgery, including lower complication rates, reduced length of stay (LOS), and improved patient outcomes (1,2). Laparoscopic adrenalectomy (LA) is the gold standard for small, benign adrenal tumours due to its proven safety and efficacy (1-3). However, large adrenal tumours (LATs) (≥6 cm) present unique challenges, such as increased technical difficulty, higher risk of intraoperative complications, and the potential for malignancy which may limit the applicability of conventional laparoscopic techniques (4).

Robotic-assisted surgery has gained traction across various surgical specialties, including urology, gynaecology, and general surgery, due to its enhanced precision, three-dimensional visualization, and improved ergonomics (5,6). In endocrine surgery, however, evidence comparing robotic adrenalectomy (RA) to conventional laparoscopy for LATs remains limited, with few randomised controlled trials (7). Despite this, emerging studies suggest that RA may offer distinct advantages in selected patient populations, including those with a high body mass index (BMI), pheochromocytomas, and larger tumours (8-13).

Rationale and knowledge gap

Descriptive case series have reported benefits of RA such as reduced blood loss, shorter hospital stays, less postoperative pain, and fewer conversions to open surgery (12,13). However, these studies are predominantly limited to large regional centres in Europe, Asia, and the United States, raising questions about the generalisability of their findings (8-13).

In the United Kingdom (UK), the adoption of robotic surgery in endocrine surgery has been slower, primarily due to high costs, limited cost-effectiveness data, and the need for specialised training (14). Despite its technical advantages, the higher upfront costs and longer setup times have limited its widespread use within the National Health Service (NHS), especially for procedures where the benefits over conventional techniques remain unclear. Nevertheless, robotic surgery could lead to long-term quality-adjusted life year (QALY) gains and reduced indirect costs, such as shorter post-op hospital stays, potentially making it cost-effective over time (10,11,15).

Given the growing interest in RA and the lack of robust comparative data, there is a need for studies evaluating the outcomes of RA versus LA in real-world clinical settings, particularly for LATs (16).

Objective

This study aims to analyse the differences in outcomes between elective laparoscopic and RA for LATs (≥6 cm) in a large tertiary referral endocrine surgery centre. By comparing key outcomes-including operative time, LOS, complication rates, conversion rates, and excision margins, this study seeks to provide insights into the comparative feasibility and safety of LA versus RA in the management of LATs. We present this article in accordance with the STROBE reporting checklist (available at https://ales.amegroups.com/article/view/10.21037/ales-25-20/rc).

Methods

This retrospective cohort study utilised a prospectively maintained database to identify all adrenalectomies performed for LATs (≥6 cm) between 2 January 2020 and September 2024 at the Royal Victoria Infirmary, Newcastle, UK. All minimally invasive adrenalectomy (robotic or laparoscopic) for LATs during this period were considered for inclusion.

Exclusion criteria were: (I) patients with strong radiological or biochemical suspicion of malignancy—such as abnormal urinary steroid profiles or imaging features concerning for carcinoma—who were managed with open adrenalectomy; (II) patients undergoing re-do or re-excision adrenalectomies; (III) patients with tumours ≤6 cm. These exclusions ensured the study focused on primary minimally invasive procedures for LATS without suspected malignancy.

All adrenal masses were evaluated based on clinical presentation, imaging findings, and functional status. Functional tumours were identified through standardised biochemical testing, including plasma metanephrines, aldosterone, renin, overnight dexamethasone suppression tests, cortisol, and adrenocorticotropic hormone (ACTH) levels as per local protocol.

Patient allocation to surgical approach was based on multidisciplinary discussions and surgeon judgment, which does introduce an element of selection bias. The RA cohort included patients selected during the early learning curve of robotic implementation, which likely influenced the complexity of cases undertaken. Although propensity score matching was considered, the small sample size limited its feasibility and statistical validity.

All surgeries were performed by one of three endocrine surgeons at a high-volume hospital: Richard Bliss (20 years’ consultant experience), P.T. (10 years), and J.R. (5 years).

Notably, estimated blood loss (EBL) was assumed to be minimal, as no specific data on blood loss were recorded in the operative notes unless significant blood loss occurred. Obesity was defined as a BMI ≥30 kg/m², in accordance with the World Health Organization (WHO) classification.

Data collected included patient demographics (age, gender, and BMI), American Society of Anaesthesiologists (ASA) grade, comorbidities (e.g., diabetes, hypertension), surgical indication (e.g., Conn’s syndrome, Cushing’s syndrome, pheochromocytoma, metastases, or indeterminate lesions), and tumour size. Outcomes assessed included operative time, conversion rates, length of hospital stay (LOS), postoperative complications, and surgical margin status. Three patients had missing BMI values, which were imputed using the median BMI from the study population to minimise bias and maintain sample size.

Statistical analysis

Statistical analysis was performed using R Studio (version 2024.12.1) and Microsoft Excel. Continuous variables were expressed as medians with interquartile ranges (IQRs), while categorical variables were expressed as absolute numbers or percentages. Univariate analyses included the Mann-Whitney U test for non-normally distributed continuous variables and Chi-squared or Fisher’s exact test for categorical variables. Multivariable linear regression was used to assess the relationship between operative time and covariates, including surgical approach, age, BMI, ASA grade, comorbidities, tumour size, and surgical indication. Multivariate logistic regression was employed to evaluate predictors of binary outcomes, such as complications and conversion rates. Interaction terms (e.g., surgical approach × tumour size) were included to explore differential effects between laparoscopic and robotic groups. Model assumptions were verified using diagnostic plots, and multicollinearity was assessed using the variance inflation factor (VIF). A P value of <0.05 (two-tailed) was considered statistically significant.

Ethical statement

This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. In accordance with our institution’s policies (Royal Victoria Infirmary) for non-experimental studies, this study was exempt from formal registration with a study registry. This was a retrospective audit using anonymised data, and individual patient consent was not required.

Results

Demographics

A total of 61 patients underwent elective adrenalectomy for LATs (≥6 cm) (Figure 1). The laparoscopic database initially included 160 cases; after excluding open surgery (n=31), redo/re-excision (n=2), and tumours ≤6 cm (n=83), 44 patients remained. The robotic cohort included 84 cases, of which 17 met the inclusion criteria after excluding those with tumours ≤6 cm (n=67).

Figure 1 Patient cohort selection. Open surgeries were included exclusively in the laparoscopic dataset. Robotic adrenalectomies were recorded in a separate database. “Open surgery” refers to procedures intended as open from the outset, rather than minimally invasive. n indicates the number of patients in each group.

The majority of patients were female: 55% (n=24) in the laparoscopic group and 65% (n=11) in the robotic group. The median age was 63 years (range, 31–86 years) in the laparoscopic group and 59 years (range, 22–76 years) in the robotic group. The median BMI was 29.7 kg/m² (range, 17.9–60.3 kg/m²) in the laparoscopic group and 27.0 kg/m² (range, 19.0–55.0 kg/m²) in the robotic group, with 37% (n=23) of patients classified as obese or morbidly obese.

Significant comorbidities included type 2 diabetes mellitus (laparoscopic: 30%, n=13; robotic: 65%, n=11), hypertension (laparoscopic: 41%, n=18; robotic: 59%, n=10), and obesity (BMI ≥30 kg/m²; laparoscopic: 41%, n=18; robotic: 35%, n=6). The distribution of ASA grades was largely similar between both groups, with 77% of patients in the laparoscopic group and 76% in the robotic group having an ASA grade of 3 (Table 1).

Surgical outcomes

In this study, all robotic and laparoscopic adrenalectomies were primarily performed using a transabdominal lateral approach. The only exception was a single bilateral case, which was performed retroperitoneally.

The mean docking time for robotic procedures was 5.6 minutes (range, 5.0–7.0 minutes), and the mean console time was 64.4 minutes (range, 31.0–150.0 minutes). Cost data obtained via the Patient Level Information and Costing System (PLICS) showed that the mean total cost for RA was £4,945.19, compared to £6,026.91 for LA. These figures include robotic equipment usage, operating theatre time, complications, medications, and LOS.

Univariate analysis showed that RAs had significantly shorter surgical times compared to laparoscopic adrenalectomies (P=0.04). Median surgical time for the laparoscopic group was 1.49 hours [standard deviation (SD) =0.70 hours, IQR =0.66 hours], and 1.03 hours (SD =0.63 hours, IQR =0.90 hours) for the robotic group (Table 2). However, multivariate analysis adjusting for age, gender, ASA score, BMI, diabetes, and hypertension, did not reveal a significant association between the surgical approach (robotic vs. laparoscopic) and surgical time (Table S1 for the main-effects model; Table S2 for the interaction model).

Notably, BMI was significantly associated with surgical time (P=0.02, 95% CI: 0.004, 0.055), with higher BMI leading to longer operative times. A significant interaction effect between the surgical group and BMI was observed, with RA being less affected by BMI compared to LA (P=0.03, 95% CI: −0.125, −0.007). However, the interaction model had poor fit, limiting the confidence in the interpretation of these interaction effects (Tables S1,S2).

Postoperative LOS was significantly shorter in the robotic surgery group compared to the laparoscopic group (P=0.047). The median LOS was 2 days (range, 1–12 days) for the laparoscopic group and 1 day (range, 1–3 days) for the robotic group respectively. Multivariate analysis adjusting for potential confounders such as age, gender, BMI, ASA score, diabetes, and hypertension did not show a significant influence of the surgical approach on the LOS (Table S3 for main-effects model; Table S4 for interaction model). Interestingly, analytical models suggest that diabetes has a significant effect on the LOS (P=0.03), with diabetic patients potentially staying 1.64 days longer than non-diabetic patients. However, this result is borderline and requires further validation.

There was no conversion to open surgery, significant adjacent organ injuries, or mortalities in either group. Two laparoscopic cases were abandoned due to adherence to the inferior vena cava medially. No significant complications (Clavien-Dindo Grade >3) occurred, and intraoperative blood loss was minimal (<50 mL) across all cases. Two patients in the laparoscopic group experienced complications not directly related to the adrenalectomy: one had postoperative surgical emphysema and ileus, and another developed hospital-acquired pneumonia (HAP). Postoperative quality of life was not assessed; future studies should incorporate this important outcome.

Tumour characteristics

Functional tumours accounted for a significant proportion of cases, with the most common tumours being pheochromocytomas in both groups. In the laparoscopic group, 34% (n=15) of cases were pheochromocytomas, 23% (n=10) were Cushing’s syndrome, and 21% (n=9) were adrenocortical adenoma. In the robotic group, 59% (n=10) of cases were pheochromocytomas, 17% (n=3) were adrenocortical adenomas, 12% (n=2) were metastases (Table 3).

Tumour size ranged from 6.0 cm upwards, with a median size of 7.5 cm (range, 6.0–12.5 cm) in the laparoscopic group and 9.0 cm (range, 6.0–12.0 cm) in the robotic group. The Wilcoxon rank-sum test comparing tumour size between the laparoscopic and robotic surgery groups showed a marginally significant difference (P=0.05), suggesting a trend toward a difference in tumour size, although the result does not reach the conventional threshold for statistical significance (P<0.05).

Pathological examination confirmed complete tumour resections with negative margins (R0) in 71% (n=30) of laparoscopic cases and 82% (n=14) of robotic cases. In the laparoscopic group, 29% (n=12) of cases had incomplete margins due to specimen disruption or fragmentation. In the robotic group, 18% (n=3) of cases demonstrated tumour involvement at the resection margin.

Discussion

Adrenalectomy is the third most commonly performed endocrine procedure in the UK. RA is an emerging technique that is increasingly adopted internationally, offering potential advantages such as enhanced dexterity, reduced operative time, and shorter LOS (15,17-19). By assessing key perioperative outcomes, our findings aim to inform the feasibility and potential role of RA in the surgical management of LATs.

Key findings

In univariate analyses, RA was associated with significantly shorter operative times and LOS compared to LA. However, after adjusting for confounding factors—including age, gender, and comorbidities—the surgical approach was no longer a significant predictor of either outcome. This suggests that patient-related variables and other contextual factors may influence these perioperative parameters.

BMI significantly affected operative time in both groups. A higher BMI was correlated with longer surgery duration in LA, whereas this relationship was slightly attenuated in RA. Nevertheless, multivariate analysis indicates that this effect may be confounded by additional variables, limiting its statistical robustness.

No mortalities directly related to either RA or LA were noted. EBL and complications were comparable between groups. Neither group experienced any conversions, limiting evaluation of the impact of surgical technique on conversion rates.

No significant differences were found between RA and LA groups in complication rates or incomplete tumour resections. R0 resection rates were higher in the RA group (82%) compared to the LA group (71%), though this difference did not reach statistical significance.

Strengths and limitations

This study draws on real-world data from a high-volume UK tertiary endocrine surgery centre, comparing RA and LA for LATs (≥6 cm). All but one procedure was performed via transabdominal lateral approach in both groups, minimising heterogeneity and thus enhancing internal validity. Furthermore, all procedures were performed by a specialised endocrine surgical team who followed consistent pre-, peri-, and post-operative protocols.

However, several limitations must be acknowledged. The retrospective, single-centre design limits causal inference and may introduce selection bias, thereby limiting generalisability of the findings. Allocation to surgical approach was based on multidisciplinary team discussions and surgeons’ judgement, rather than formal randomisation. This may have influenced case complexity and limited comparability between groups. Additionally, the relatively small sample size, particularly given the imbalance between the laparoscopic and robotic groups, limits statistical power to detect subtle differences in outcomes and increases the risk of type II error.

Larger multi-centre randomised controlled trials (RCTs) are needed to confirm these findings and to evaluate the long-term clinical outcomes of RA compared to LA. Despite these limitations, this study contributes valuable data to the ongoing debate about the feasibility, safety, and potential benefit of RA compared to LA for LATs.

Comparison with similar research

Current literature suggests that RA is associated with significantly shorter surgical times compared to LA, particularly in obese patients (7,8,10,15,20). For instance, Isiktas et al. and Zhao et al. reported superior operative times in RA for obese patients, consistent with our findings (7,21). However, conflicting evidence exists. Some studies, such as those by Aksoy et al. and Shalaby et al., found that operative times in RA were either similar or slightly longer than those in LA for obese patients (12,22). Variations in study design, such as the definition of operative time, differences in robotic system setup times (e.g., docking and undocking), and case complexity may explain these inconsistencies. Future studies should better control for these variables to more accurately assess the true impact of BMI on surgical time, thereby facilitating the refinement of patient selection criteria.

Consistent with Agcaoglu et al., we found no significant differences in complication rates or incomplete tumour resection between approaches in obese patients (20).

Our study found that the median postoperative LOS was significantly shorter in the robotic group compared to the laparoscopic group, consistent with previous meta-analyses by Economopoulos et al. and Gan et al., which indicate faster recovery time with RA (10,23). However, after adjusting for factors like age, gender, and comorbidities, there was no significant association between surgical approach and LOS, suggesting that other variables, including patient comorbidities, pre-operative functional status and psychosocial factors, may play a crucial role in postoperative recovery.

Current literature reports comparable conversion rates and EBL between RA and LA, as reflected in our study (10,15,17).

Explanations of findings

In our study, all adrenalectomies were performed via a transabdominal lateral approach except for one bilateral case done retroperitoneally. Retroperitoneal adrenalectomy (RPA) is a recognised technique. However, it is typically reserved for smaller tumours (<4 cm), bilateral disease, patients with favourable BMIs, or those with prior major abdominal surgery in our institution. While robotic RPA is possible, patient selection tends to be more restrictive than with the transperitoneal lateral approach.

In our cohort, RA was associated with significantly shorter surgical times compared to LA. This is likely attributable to the advanced capabilities of robotic systems, which provide fine-tuned articulating instruments, high-definition three-dimensional visualisation, and enhanced camera platforms (11,15). These features may facilitate more efficient dissection and improved access to challenging anatomical structures (8,10,12,20). However, after adjusting for confounding factors such as age, gender, ASA score, BMI, diabetes, and hypertension, multivariate analysis showed no significant association between surgical approach and operative time. These results suggest that factors beyond the surgical approach, such as surgeon experience, case complexity, and patient body habitus, may influence operative time (4,10,21).

Our study demonstrated that BMI significantly influenced surgical time for both LA and RA. Higher BMI was associated with longer surgical durations in laparoscopic procedures, whereas this relationship was less pronounced in robotic surgeries. This suggests that the RA’s enhanced dexterity and precision may better mitigate the challenges of higher BMI than LA. However, the regression model assessing this interaction had low explanatory power, indicating limited ability to fully capture the relationship. Unmeasured confounding variables or noise in the data may contribute to this finding, which warrants cautious interpretation.

In our cohort, neither the robotic nor the laparoscopic surgery group experienced any conversions, precluding any meaningful conclusions about the impact of surgical technique on conversion rates. However, current literature reports comparable conversion rates between RA and LA (10,15,17). Additionally, while EBL was not explicitly recorded in our surgical notes, available literature evidence suggests minimal differences in EBL between RA and LA, as EBL in LA is already minimal at baseline (10,15). This supports the notion that both surgical techniques are effective in controlling intraoperative bleeding and ensuring patient safety.

A marginally significant difference in tumour size was observed between the groups, with the robotic group having slightly larger tumours. This suggests that the enhanced manoeuvrability and visualisation offered by RA may confer advantages when resecting larger and more complex tumours (8-11). Despite this trend, further research with larger sample sizes is required to definitively establish the relationship between tumour size, surgical approach, and surgical outcomes.

In terms of surgical margins, R0 resection was achieved in 82% of robotic cases compared to 71% of laparoscopic cases. Although this difference did not reach statistical significance, it suggests a trend towards better margin clearance with robotic surgery. However, in the laparoscopic group, incomplete margins were primarily due to specimen disruption or fragmentation (29%), which could introduce bias in the assessment of margin status. Therefore, these results should be interpreted with caution. Overall, while the data suggests that RA may facilitate more precise tumour dissection, particularly in complex anatomical areas, the lack of a statistically significant difference between the two groups indicates that the high efficacy of laparoscopic surgery in the hands of experienced surgeons may mitigate the potential advantages of RA.

Implications and actions needed

Our results support both RA and LA as safe, effective options for managing LATs. RA may offer advantages in operative time and precision, particularly in obese patients, although these outcomes were not independently associated with surgical approach after adjustment for confounding variables.

Prospective, adequately powered studies are required to evaluate the long-term outcomes of RA versus LA, particularly regarding oncological safety, cost-effectiveness, and quality of life. Standardising the definitions and the measurement of key outcomes such as docking, console times for RA, EBL, and margin status will enhance comparability across studies.

Conclusions

This study demonstrates that RA can be a feasible and effective alternative to LA for patients with LATs (≥6 cm). While RA was associated with shorter operative time and LOS in univariate analysis, these differences were not statistically significant after adjusting for confounders. Importantly, however, RA appeared less affected by increasing BMI, suggesting a potential benefit in patients with higher BMI. Future RCTs should compare robotic and laparoscopic adrenalectomies in larger, more diverse cohorts, with an emphasis on long-term outcomes, cost-effectiveness, and identifying specific patient populations that would benefit most from RA.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://ales.amegroups.com/article/view/10.21037/ales-25-20/rc

Data Sharing Statement: Available at https://ales.amegroups.com/article/view/10.21037/ales-25-20/dss

Peer Review File: Available at https://ales.amegroups.com/article/view/10.21037/ales-25-20/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://ales.amegroups.com/article/view/10.21037/ales-25-20/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 and its subsequent amendments. In line with institutional policies of Royal Victoria Infirmary for non-experimental studies, formal registration with a study registry was not required. Patient data were anonymised to ensure confidentiality. Individual patient consent was not required.

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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