Relevance of robotic surgery for thymoma: a narrative review
Review Article

Relevance of robotic surgery for thymoma: a narrative review

Masahiro Miyajima, Atsushi Watanabe

Department of Thoracic Surgery, Sapporo Medical University, Sapporo, Japan

Contributions: (I) Conception and design: Both authors; (II) Administrative support: A Watanabe; (III) Provision of study materials or patients: M Miyajima; (IV) Collection and assembly of data: M Miyajima; (V) Data analysis and interpretation: M Miyajima; (VI) Manuscript writing: Both authors; (VII) Final approval of manuscript: Both authors.

Correspondence to: Atsushi Watanabe, MD, PhD. Department of Thoracic Surgery, Sapporo Medical University, Chuo-Ku S1 W16, Sapporo 060-8543, Japan. Email: atsushiw@sapmed.ac.jp.

Background and Objective: Thymectomy with median sternotomy is the gold standard for thymoma and myasthenia gravis, although minimally invasive procedures such as robot-assisted surgery have recently become more common. However, the superiority of these approaches has not been established, and they are infrequently recommended for localized lesions. The International Thymic Malignancies Interest Group warned that despite the perceived reduction in length of hospital stay and pain, the benefits of these approaches compared to the open approach have not been fully substantiated and that prospective collaborative data collection is critical in defining the value of these techniques. Whether thymectomy is necessary for stage I thymomas in the absence of myasthenia gravis or anti-acetylcholine receptor antibodies is also unclear. This study reviews and discusses the literature on this subject.

Methods: A narrative review was conducted using PubMed and Scopus databases. Original research articles comparing robotic to video-assisted thoracic surgery or to open thymectomy for thymomas were included. A comparison of partial resection and total thymectomy (thymothymectomy) for thymomas was also conducted.

Key Content and Findings: Perioperative outcomes such as blood loss, operative duration, complications, and length of hospital stay were better for robot-assisted resection of early-stage thymomas than for open thymoma surgery. It would be premature to consider partial resection as an appropriate treatment option for thymomas.

Conclusions: Robotic thymothymectomy is safe with effective and promising long-term results and oncological and surgical outcomes in patients with thymoma. Robotic thymectomy can become the standard procedure in patients with early-stage thymomas.

Keywords: Robotic surgery; thymoma; da Vinci; thymectomy

Received: 22 August 2023; Accepted: 06 March 2024; Published online: 21 May 2024.

doi: 10.21037/med-23-37

Introduction

Background

Thymomas are rare neoplasms that exhibit a wide range of behaviors, from indolent to fatal (1). However, several unanswered questions require further research. Thymectomy is the standard procedure for thymoma treatment and an important component of multidisciplinary treatment for myasthenia gravis. Although there are several approaches to thymectomy, including minimally invasive approaches, median sternotomy remains the golden standard (2). However, in recent years, treatment methods have changed significantly with the widespread use of minimally invasive approaches. The advent of robot-assisted surgery has led to several innovations. Since Yoshino et al. first performed robotic surgery for thymoma in 2001, various approaches to robotic surgery have been developed (3). Although the use of video-assisted thoracic surgery (VATS) or robot-assisted thoracic surgery (RATS) has increased in recent years, its superiority over conventional open thoracic surgery has not been established, and it is infrequently recommended as an approach for localized lesions (4-6). It is unclear whether thymectomy is necessary for stage I thymomas without symptoms of myasthenia gravis or the presence of anti-acetylcholine receptor antibodies. Although the extent of resection is not of considerable concern with sternotomy, the difficulty of complete dissection has led to a debate that should be resolved as minimally invasive approaches become more popular: whether thymectomy is necessary for localized thymomas or localized resection is sufficient (Figure 1). No coherent reports on this subject have been reported and no definite conclusions have been drawn. Therefore, we review and discuss the literature on this subject.

Figure 1 Extent of resection. Partial thymectomy removes a portion of the thymus gland with a margin from the tumor (solid line); thymothymectomy removes the same area as a total thymectomy (dotted line).

The curative treatment for thymic epithelial tumors is surgical resection. If thymic epithelial tumors are suspected on imaging and complete resection is possible, surgical treatment is performed without pathological biopsy. The principal surgical technique is thymectomy through median sternotomy. In particular, patients with myasthenia gravis are indicated for extended thymectomy, wherein the fatty tissue below the thyroid gland in the anterior cervical region is resected.

Rationale and knowledge gap

The thoracoscopic approach to stage I–II thymomas is an acceptable technique according to the Japanese guidelines, though the level of evidence is low (4-8). The Japanese guidelines have provided the same level of recommendation as for thoracoscopic surgery. However, minimally invasive surgery is not routinely recommended in the National Comprehensive Cancer Network guidelines because of the lack of long-term results and evidence (9-13).

Objective

The use of robotic surgery for thymomas has increased in recent years. We outline the protocol for robotic surgery for thymoma, and review the literature to clarify the suitability of the robotic surgical approach and the extent of resection that should be performed. In addition, we also consider whether thymectomy is necessary or partial resection is sufficient in cases of localized thymoma. We present this article in accordance with the Narrative Review reporting checklist (available at https://med.amegroups.com/article/view/10.21037/med-23-37/rc).

Methods

Literature search strategy

Thymectomy-specific publication searches were conducted using PubMed and Scopus databases to find relevant publications for this clinical evaluation (Table 1). Publication searches were conducted as listed: (robot[All Fields] OR robot assist[All Fields] OR robotic[All Fields] OR da vinci[All Fields] AND “surgery”[all fields] AND “thymoma”[all fields]).

Table 1

The search strategy summary

Items Specification
Date of search January 1st, 2023 and August 31st, 2023
Databases and other sources searched PubMed, Scopus
Search terms used MeSH: (robot[All Fields] OR robot assist[All Fields] OR robotic[All Fields] OR da vinci[All Fields] AND “surgery”[all fields] AND “thymoma”[all fields])
Timeframe From January 2010 to August 2023
Inclusion criteria and exclusion criteria Inclusion: original articles, review. Exclusion: case report, abstract of meeting
Selection process M.M. and A.W. conducted the selection. Consensus of all authors was obtained

All citations returned from the above searches were exported into an EndNote library. Duplications were removed and titles and abstracts were reviewed by two authors (M.M., A.W.) for inclusion in the library.

Review

Surgery

For reference, we outline the protocol of thymoma surgery used in our department. Since 2018, we have been performing robotic surgery for thymomas using the da Vinci Xi Surgical System (Intuitive Surgical Inc., Sunnyvale, CA, USA) in our department (14). The patient’s position is shown in Figure 2. The robotic 8 mm port was placed between the second and eighth intercostal spaces, according to the patient’s physique. Four robotic arms were placed (Figure 2). Fenestrated bipolar forceps, an 8-mm endoscope, Maryland-type bipolar forceps, and Vessel Sealer Extend (Intuitive Surgical Inc.) were used. The port placed at the sixth intercostal space was used as an assistant port with a 12-mm air-seal port (Medical Leaders Inc., Tokyo, Japan). The intraoperative thoracic carbon dioxide insufflation pressure was set at 8–10 mmHg. The thymus with the thymoma was removed through a 30 mm or larger assistant port or extended port incision. In our department, we performed median sternotomy for tumors larger than 5 cm. However, as we became more proficient with this technique, we expanded its use to include larger tumors.

Figure 2 Port placements. Robotic 8-mm ports were placed in the second, fourth, sixth and seventh intercostal space. Then, an assistant port with a 12-mm air seal port placed in the sixth intercostal space.

Comparison of RATS, VATS, and open surgery

Historically, prudence has been required while using minimally invasive approaches to thymic tumors because of the risk of damaging the tumor capsule, which may increase the risk of local recurrence (13,15,16). With the application of minimally invasive surgeries for thymomas, the International Thymic Malignancies Interest Group (ITMIG) proposed several standard policies in 2011. “To ensure an adequate margin of safety, thymomas should be resected with the surrounding normal thymus and fat”. Intact thymic tissue and perithymic fat should be used for tumor grasping and traction in a “no touch” technique that avoids the risk of capsular rupture (17). It should be noted that capsular rupture makes analysis by the pathologist difficult, so to avoid the risk of rupture, the utility incision must be adapted so that the capsule does not rupture in the extraction bag when the specimen is removed. ITMIG warned that despite the perceived reduction in length of hospital stay and pain, the benefits of these approaches in comparison to those of the open approach have not been fully substantiated, and that prospective collaborative data collection is critical in defining the value of these techniques.

Recently, the number of reports on robot-assisted surgery has increased. Perioperative outcomes with robot-assisted surgery are better than with open or thoracoscopic approaches while comparable outcomes to those with thoracoscopic approaches have been reported (16,18-24) (Tables 2,3). Regarding long-term prognosis, the 5-year overall survival did not differ significantly between thoracoscopic and open approaches, although both groups included stage III or higher cases (21,22). Only Yang et al. found the 5-year overall survival difference in minimally invasive cardiothoracic surgery (MICS) vs. open (90.7 vs. 86.9 months, P=0.04), but this difference was lost after propensity score matching (PSM) (89.4 vs. 81.6 months, P=0.2) (22). However, long-term outcomes beyond 10 years remain unclear. Furthermore, open thoracotomy has been compared with thoracoscopic surgery, including robot-assisted surgery, using PSM adjusted for confounding factors, but significant differences in short-term prognosis, long-term prognosis, or perioperative outcomes have not been reported, despite significant differences in length of hospital stay (18,21,23).

Table 2

Study characteristics of thymothymectomy according to robotic, thoracoscopic and open approaches

Author Study year Study design Duration Study arm Sample size Approach Age (years)† Thymoma stage Follow-up interval†
Balduyck (20) 2011 PC 2004–2008 R 14 Rt or Lt multiport 49 [18–63] A: 1, B1: 2, B2: 1, AB: 1 34 mo
O 22 Median sternotomy 56 [23–84] A: 1, B1: 2, B2: 5, B3: 1, AB: 3 50 mo
Burt (18) 2017 ITMIGDB 1997–2012 R 146 NA 56 [15–85] MICS I: 199, II: 186, III: 27, IV: 12 NA
VATS 315 NA NA NA NA
O 2,053 Sternotomy/thoracotomy 54 [8–88] I: 669, II: 654, III: 344, IV: 130 NA
Qian (19) 2017 RC 2009–2014 R 51 Rt or Lt, 3-port 49±13 I: 19, IIA: 21, IIB: 21 421±469 d
VATS 35 Rt or Lt, 3-port 50±13 I: 10, IIA: 14, IIB: 11 701±382 d
O 37 Median sternotomy 47±14 I: 10, IIA: 12, IIB: 15 818±592 d
Ye (16) 2013 RC 2009–2012 R 21 Rt or Lt, 3-port 53±8 I: 21 17 [6–48] mo
VATS 25 Rt or Lt, 3-port 53±5 I: 25 25 [6–48] mo
Marulli (24) 2018 RCC-PSM 1982–2017 R 41 Rt or Lt, multiport 58±11 I: 8, II: 33 28 [18–61] mo
O 41 Mediansternotomy 58±10 I: 9, II: 32 88 [62–116] mo
Yang (22) 2020 NCDB 2010–2014 R 176 NA 59.6±12.7 I-IIa: 203: Iib:77, III: 37 35.9 [24.9–52.2] mo
VATS 141 NA NA NA 40.7 [27.3–56.8] mo
O 906 Sternotomy/thoracotomy 57.4±14.1 I-Iia: 432, Iib: 196, III: 278 NA
Yang (22) PSM 2020 NCDB-PSM 2010–2014 MICS 185 NA 61.6±10.4 I-Iia: 110, Iib: 49, III: 26 36.4 [25.8–55.4] mo
O 185 Sternotomy/thoracotomy 62.6±11.1 I-Iia: 116: Iib: 40, III: 29 35.9 [25.4–50.5] mo
Kamel (23) 2019 NCDB 2010–2014 R 300 NA 63 [54–72] 4.5 (range, 3.1–6.3) cm NA
VATS 280 NA 62 [53–70] 5.0 (range, 3.5–7.8) cm NA
Kamel (23) PSM 1 2019 NCDB-PSM 2010–2014 R 197 NA 62 5.0 cm NA
VATS 197 Sternotomy/thoracotomy 62 5.3 cm NA
Kamel (23) PSM 2 2019 NCDB-PSM 2010–2014 R 272 NA 61 5.1 cm NA
O 272 NA 61 5.1 cm NA

†, data are presented as mean ± standard deviation or mean [range]. Yang matched: age, sex, race, Charlson-Deyo comorbidity score, regional education levels, tumor size, insurance type, histology, stage, year of diagnosis, distance from facility, and facility type. Kamel matched: age, gender, Charlson comorbidity index, induction therapy, tumor size and tumor extension. PC, prospective study; R, robotic; O, open approach; Rt, right; Lt, left; mo, months; ITMIGDB, International Thymic Malignancy Interest Group Database; NA, not applicable (not reported); VATS, video-assisted thoracic surgery; MICS, minimally invasive cardiothoracic surgery; RC, retrospective cohort; d, days; PSM, propensity score matching; RCC-PSM, retrospective case control study using PSM; NCDB, National Cancer Database; NCDB-PSM, NCDB study using PSM.

Table 3

Outcomes of robotic thymectomy by other approaches

Author Study arm Sample size Operative time (min)† P value Blood loss (mL)† P value In-hospital duration (days)† P value Conversion rate (%) P value 5-year overall survival (%) P value Mortality (in-hospital or 30-day, %) P value R0 resection (%) P value
Balduyck (20) R 14 224.2±66.5 NS NA – 9.6±3.9 NS 7.1 – NA – 0 NS NA –
O 22 243.8±55.5 – NA – 11.8±5.7 – NA – NA – 0 – NA –
Burt (18) O 146 NA – NA – NA – 0 – NA – 0 NS 92 0.2
VATS 315 NA – NA – NA – NA – NA – 0 – 86 –
2,053 NA – NA – NA – NA – NA – – – NA –
Qian (19) O 51 71.2±39.8 – 77.5±69.5 – 4.3±1.1 <0.001 0 – NA – 0 NS NA –
VATS 35 88.5±37.6 – 246±316.5 v 6.6±1.4 – NA – NA – 0 – NA –
37 NA – NA – NA – NA – NA – – – NA –
Ye (16) R 21 97±38 – 61.3±21.9 <0.01 3.7±1.1 <0.01 0 – NA – NA – NA –
O 25 214.5±35.4 – 466.1±91.4 – 11.6±10.4 – NA – NA – NA – NA –
Marulli (24) R 41 132.5 [115–170] <0.001 NA – 3 [3–4] <0.01 3.5 – NA – 0 NS 100 NS
O 41 115 [90–137] – NA – 6 [5–7] – NA – NA – 0 – 100 –
Yang (22) MICS 317 NA – NA – NA – NA – 90.7 0.04 NA – NA –
O 906 NA – NA – NA – NA – 86.9 – NA – NA –
Yang (22) PSM MICS 185 NA – NA – 3 [2–4] <0.001 19 – 89.4 0.2 <10 NS 76.2 0.84
O 185 NA – NA – 4 [3–5] – NA – 81.6 – <10 – 69.7 –
Kamel (23) PSM 1 R 197 NA – NA – 4±5 0.76 23 0.031 93 0.571 1 NS 50 0.47
VATS 197 NA – NA – 4±5 – 11 – 94 – 2 – 57 –
Kamel (23) PSM 2 R 272 NA – NA – 4±8 0.057 NA – 91 0.094 1 NS 32 0.13
O 272 NA – NA – 5±7 – NA – 80 – 2 – 47 –

†, data are presented as mean ± standard deviation or mean [range]. R, robotic; O, open approach; NS, not significant; NA, not applicable (not reported); VATS, video-assisted thoracic surgery; MICS, minimally invasive cardiothoracic surgery; PSM, propensity score matching.

Perioperative outcomes such as blood loss, operative duration, respiratory complications, and postoperative length of hospital stay were better for thoracoscopy-assisted resection of stage I−II thymic epithelial tumors than for open thoracic surgery (4,5,9). However, there was no significant difference in the R0 resection rate, which was approximately 80% with both techniques (7,8).

Our previous study revealed that RATS offers the advantage of improved postoperative quality of life according to nursing care systems compared with VATS (14). We found no significant differences in pain between patients with either of the two techniques, at the first and second follow-up visits, although RATS involved the use of more ports and intercostal space access than VATS (14). Şehitogullari et al. reported no significant differences in postoperative pain between patients with RATS and VATS (25). Kamel et al. found the differences in conversion rates in VATS and RATS (23% vs. 11%, P=0.031) (23).

However, many other references report no or little difference. This may be due to differences in facility criteria for conversion.

In recent years, the RATS approach has been used in patients with large thymomas. However, data are scarce. In the existing literature, most investigators warn against the routine use of RATS for thymomas larger than 4 cm (26). How far can the surgeons push the limits of robot-assisted surgery?

Kneuertz et al. performed the single institution retrospective study to compare the safety and feasibility of RATS (n=20) and open approach (n=34) for thymoma larger than 4 cm using the PSM (27). They demonstrated that robotic assisted thymectomy is a safe and effective approach even for patients with large thymomas, which can be performed in similar radical fashion and with a high rate of complete resection compared with the traditional open procedure (complication rate: 15% vs. 24%, P=0.45; R0: 90% vs. 85%, P=0.62).

Bongiolatti et al. retrospectively reviewed 106 thymectomies from 2010 to 2020, creating two groups based on the surgical approach (open or RATS) and size (28). Kaplan-Meier and Cox regression were used to estimate and identify risk factors of oncological outcomes. To perform a well-balanced analysis, a PSM analysis was conducted for large thymomas. They performed 54 RATS thymectomies and 46.3% (n=24) were large thymomas (larger than 5 cm). All patients had a complete resection. The median and the overall survival rate for larger tumor were similar between RATS and open (109 vs. 67 months, 92% vs. 83%, P=0.95).

Extent of resection for thymoma surgery

Because of the need for complete resection and the high incidence of myasthenia gravis, thymoma treatment is usually total thymectomy or complete tumor resection. However, in recent years, improvements in minimally invasive thoracic surgery (video- or robot-assisted) have encouraged thoracic surgeons to treat smaller thymomas by performing partial resections rather than resecting the entire thymus gland and thymoma (29-33) (Tables 4-6).

Table 4

Study characteristics of partial thymectomy and thymothymectomy for thymoma

Author Study year Study design Duration (year) Study arm Sample size, open Age (years), mean ± SD Diagnosis Thymoma stage Follow-up interval [range], mo
Narm (29) 2016 RC 2000–2013 Limited 295 49±13 Masaoka-Koga I: 161, IIA: 70, IIB: 64 48 [0.3–189]
Total 467 52±12 Masaoka-Koga I: 241, IIA: 147, IIB: 79 50 [0.2–178]
Narm (29) PSM 2016 RCC-PSM 2000–2013 Limited 141 50±14 Masaoka-Koga I: 80, IIA: 34, IIB: 27 48 [0.3–189]
Total 141 50±12 Masaoka-Koga I: 88, IIA: 28, IIB: 25 50 [0.2–178]
Nakagawa (30) 2016 RC 1991–2010 Limited 289 61.1±13.2 Masaoka I: 174, II: 115 NA
Total 997 57.0±13.2 Masaoka I: 479, II: 518 NA
Nakagawa (30) PSM 2016 RCC-PSM 1991–2010 Limited 276 60.6±13.2 Masaoka I: 161, II: 115 48
Total 276 61.0±11.9 Masaoka I: 158, II: 118 59
Gu (31) 2016 RC 1994–2012 Limited 251 52.3±11.9 Masaoka I: 178, II: 73 38
Total 796 50.9±12.2 Masaoka I: 523, II: 273 38
Guerrera (32) 2021 RC 1994–2012 Limited 30 65.9±10.8 Masaoka T1a: 26, T1b: 4 37 [17–72]
Total 441 60.9±13.0 Masaoka T1a: 388, T1b: 53 37 [17–72]
Guerrera (32) PSM 2021 RCC-PSM 1994–2012 Limited 30 65.9±10.8 Masaoka T1a: 26, T1b: 4 37 [17–72]
Total 90 65.0±11.3 Masaoka T1a: 79, T1b: 11 NA
Yano (33) 2017 PC 2007–2011 Limited 36 61±12 Masaoka I: 22, II: 14 63.1

Narm matched: age, sex, surgical approach, tumor size, WHO histology type, Masaoka-Koga stage, and adjuvant radiotherapy. Nakagawa matched: age, sex, tumor size, WHO histologic subtype, Masaoka stage, and adjuvant radiotherapy. Guerrera matched: age, gender, cardiac comorbidity, other comorbidities, thymoma size, surgical approach, WHO histology and pathological TNM. SD, standard deviation; mo, months; RC, retrospective cohort; PSM, propensity score matching; RCC-PSM, retrospective case control study using PSM; NA, not applicable (not reported); PC, prospective cohort; WHO, World Health Organization.

Table 5

Outcomes of partial thymectomy and thymothymectomy for thymoma

Author Study arm Sample size Operative time (min), mean [range] P value Blood loss (mL), mean [range] P value Complication rate (%) P value In-hospital duration (days) P value MICS rate (%) P value
Narm (29) Limited 295 NA – NA – NA – NA – VATS: 71.9; sternotomy: 17.3; *others: 10.8 <0.01
Total 467 NA – NA – NA – NA – VATS: 18.2; sternotomy: 73.2; *others 8.6 –
Narm (29) PSM Limited 141 110 [72–136] <0.01 50 [0–200] <0.01 7 0.55 5 0.95 VATS: 51.1; sternotomy: 34.0; *others: 14.9 0.44
Total 141 133 [112–165] – 150 [35–300] – 5 – 5 – VATS: 53.9; sternotomy: 33.3; *others: 12.8 –
Nakagawa (30) PSM Limited 276 NA – NA – 12 0.0397 NA – NA –
Total 276 NA – NA – 23 – NA – NA –
Gu (31) Limited 251 NA – NA – NA – NA – VATS: 22.8; thoracotomy: 68; sternotomy: 9.2 <0.001
Total 796 NA – NA – NA – NA – VATS: 27.6; thoracotomy: 9.8; sternotomy: 62.6 –
Guerrera (32) Limited 30 NA – NA – 62 0.079 NA – MICS: 70 <0.001
Total 441 NA – NA – 4 – NA – MICS: 25.4 –
Guerrera (32) PSM Limited 30 NA – NA – NA – NA – MICS: 70 0.91
Total 90 NA – NA – NA – NA – MICS: 71 –
Yano (33) Limited 36 NA – NA – NA – NA – VATS: 29, sternotomy: 5, thoracotomy: 2 –

*others = missing data. MICS, minimally invasive cardiothoracic surgery; NA, not applicable (not reported); VATS, video-assisted thoracic surgery; PSM, propensity score matching.

Table 6

Long-term outcomes of partial thymectomy and thymothymectomy for thymoma

Author Study arm 5-year DFS P value 10-year DFS P value 5-year OS P value 10-year OS P value Mortality (%) P value R0 (%) P value Recurrence rate (%) P value
Narm (29) Limited NA – NA – NA – NA – NA – NA – 11 0.1
Total NA – NA – NA – NA – NA – NA – 19 –
Narm (29) PSM Limited 96.3% 0.86 89.7% 0.86 94.1% 0.82 86.8% 0.82 17 0.65 96.5 0.76 7 >0.99
Total 97% – 85% – 96.9% – 86.0% – 23 – 95.7 – 5 –
Nakagawa (30) PSM Limited 93.8% 0.588 NA – 97.3% 0.487 NA – 1 NS 97.8 0.142 11 0.102
Total 94.9% – NA – 96.9% – NA – 1 – 99.3 – 5 –
Gu (31) Limited NA – NA – NA – 89.4% 0.732 1 NS 98.4 0.267 Stage I: 1.4; stage II: 14.5 Stage I: 0.259
Total NA – NA – NA – 90.9% – 1 – 98.7 – Stage I: 3.1; stage II; 2.9 Stage II: 0.001
Guerrera (32) Limited 79% <0.001 NA – 55% 0.002 NA – 2 0.23 94.6 0.83 NA –
Total 96% – NA – 89% – NA – 12 – 93.7 – NA –
Guerrera (32) PSM Limited 79% 0.025 NA – 49% 0.144 NA – NA – NA – NA –
Total 98% – NA – 80% – NA – NA – NA – NA –
Yano (33) Limited 94.1% – NA – 94.1% – NA – 2 – NA – 0 –

DFS, disease free survival; OS, overall survival; NA, not applicable (not reported); PSM, propensity score matching; NS, not significant.

In 2016, three articles based on a large national thymus database reported the results of a comparative analysis between partial thymectomy and thymothymectomy. Narm et al. used data from the Korean Association for Research on the Thymus Registry. They did not report a significant difference in the recurrence rate of thymoma (29). PSM analysis was performed on data pertaining to 141 patients selected from each group. The 5- and 10-year recurrence-free rates in the partial thymectomy group were 96.3% and 89.7%, respectively, whereas those in the thymothymectomy group were 97.0% and 85.0%, respectively (P=0.86).

In contrast, an analysis of The Japanese Association for Research on the Thymus (JART) database, a prospective study conducted by the Japanese Thymus Study Group (30), and the Chinese Alliance for Research in Thymoma reported a higher recurrence rate in the partial resection group (31). In the JART study, 276 pairs of patients with stage I (T1N0M0) thymomas were compared using PSM. The 5-year overall survival rate was 97.3% in the partial thymectomy group and 96.9% in the thymothymectomy group (P=0.487); hence, local recurrence in the partial thymectomy group was more frequent than in the thymothymectomy group (2.2% vs. 0.4%, P=0.0613). The Chinese Alliance for Research in Thymomas enrolled patients with stage I and II thymomas. They reported similar 10-year overall survival between the two groups (90.9% after thymothymectomy and 89.4% after partial thymectomy, P=0.732). Overall, the recurrence rates were 3.1% after thymothymectomy and 5.4% after partial thymectomy, with no significant difference between the two groups (P=0.149). However, this study had some limitations. In the case of partial thymectomy, the possibility of incomplete resection was high, particularly in patients with stage II disease (2.9% vs. 14.5%) (31).

In 2021, Guerrera et al. published a study comparing short- and long-term outcomes of partial thymectomy and thymothymectomy in patients with non-myasthenia gravis stage I thymoma using the European Society of Thoracic Surgeons Thymic Database. The 5-year overall survival (55% vs. 89%) and 5-year disease-free survival (79% vs. 96%) of patients who underwent partial thymectomies were worse than those of patients who underwent thymothymectomies (32). This result suggests that we cannot perform partial resection for thymoma with impunity. Future prospective randomized studies are needed to evaluate the extent of resection in early-stage thymoma surgery.

In 2017, Yano et al. evaluated the efficacy of partial or subtotal thymectomy for early-stage thymoma in the prospective study (33). Thirty-three out of 36 patients underwent partial resection of the thymus and all patients remained recurrence-free with the mean follow-up of 63 months. According to the authors, preserving the thymus could benefit the rest of one’s life as an immunological supplement against future diseases. Some surgeons believe that thymomas behave docilely and complete resection is not required. Choe et al. performed a retrospective study of 72 patients who underwent resection of thymic epithelial tumors with de novo metastasis to the pleura or pericardium (34). Patients with negative or microscopically positive R0 or R1 resection margins were compared with those with grossly positive margins (R2). The overall survival was 11.8 vs. 5.5 years, respectively. In the present study, incomplete resection was identified as a major negative predictive factor for overall survival. Therefore, it would be premature to consider partial thymectomy as an appropriate treatment for thymoma.

Drawbacks of robotic surgery

Robotic surgery has several limitations including the high cost, lack of tactile sensation, annual maintenance costs, and expensive disposable robotic equipment. However, some of these limitations can be countered by the interdisciplinary use of robots (35). The interference of surgical instruments in the narrow mediastinum, which was a problem with VATS, has been eliminated with RATS, coupled with the expansion of the surgical field by CO2 insufflation. Furthermore, in recent years, robots with tactile senses have been developed and proven to be effective, yet robots currently in widespread use do not have antennae (36). It should also be noted that it can take time to respond to unexpected injuries or bleeding from the innominate vein.

Drawbacks of partial thymectomy

Some studies claim that partial thymectomy has a lower complication rate, less operative time and less blood loss. However, consideration should be given to the increased likelihood of incomplete resection with limited resection of the thymus, especially in stage II, as shown in a study by the ChaRT study (2.9% vs. 14.5%) (31). In addition, partial resection of the thymus could not secure the safe anatomic margins and eventually could lead to leave behind multifocal thymic epithelial tumors (37,38). The final stage is established on the pathological examination of the specimen, sometimes the diagnosis is corrected compared to preoperative imaging. We should keep in mind these drawbacks when considering the partial thymectomy for thymoma. Furthermore, it is important to note that performing partial resection does not allow node removal following the 2015 ITMIG recommendations (39).

Limitations

Our narrative review has some limitations. First, considering the advances in RATS technology, we basically excluded an article published before 2010. This may have resulted in selection bias. Furthermore, there is still a lack of sufficient long-term outcome data to analyze the survival rates of RATS and Open approaches for early-stage thymoma.

Conclusions

Robotic thymectomy is a proven procedure performed at many centers. Current data indicate that it is safe with effective and promising long-term results and oncological and surgical outcomes in patients with thymoma. Future prospective randomized studies are needed to evaluate its superiority over the standard thoracoscopic techniques. Robotic thymectomy can become the standard procedure in patients with early-stage thymomas. Furthermore, it is premature to consider partial thymectomy as an appropriate treatment for thymomas.

Acknowledgments

We would like to thank Editage (www.editage.jp) for English language editing.

Funding: None.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://med.amegroups.com/article/view/10.21037/med-23-37/rc

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Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-23-37/coif). The authors have no conflicts of interest to declare.

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doi: 10.21037/med-23-37
Cite this article as: Miyajima M, Watanabe A. Relevance of robotic surgery for thymoma: a narrative review. Mediastinum 2024;8:29.

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