Trans-oral robotic surgery in the management of parapharyngeal space tumors: A systematic review

Oral Oncology 103 (2020) 104581

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Review

Trans-oral robotic surgery in the management of parapharyngeal space tumors: A systematic review

T

Armando De Virgilioa,b, , Andrea Costantinob, Giuseppe Mercantea,b, Pasquale Di Maioc, Oreste Ioccaa, Giuseppe Sprianoa,b ⁎

a

Humanitas University, Via Rita Levi Montalcini, 4, 20090 Pieve Emanuele (MI), Italy Department of Otorhinolaryngology Head and Neck Surgery, IRCCS Humanitas Clinical and Research Center, Via Alessandro Manzoni, 56, 20089 Rozzano (MI), Italy c Department of Otolaryngology-Head and Neck Surgery, Giovanni Borea Civil Hospital, Sanremo, Italy b

ARTICLE INFO

ABSTRACT

Keywords: TORS Parapharyngeal space Robotic surgery Trans-oral Parapharynx

Purpose: To perform a systematic review of studies evaluating Trans-oral Robotic Surgery (TORS) in the treatment of parapharyngeal space (PPS) tumors. Methods: A comprehensive electronic search was performed in PubMed/MEDLINE, Cochrane Library, and Google Scholar databases for appropriate published studies. The last search was conducted on November 9, 2019. Results: Twenty-two studies were included for the systematic review which analyzed a total of 113 patients (median age 53.5, IQR 41.5–58.1). The most common PPS tumor treated with TORS was the pleomorphic adenoma (n = 66; 58.4%). All tumors were successfully resected. The median tumor size was 4.8 cm (n = 73; IQR 3.8–5.4). Combined transcervical (TORS-TC) and transparotid (TORS-TP) approaches were used in 13 (11.5%) and 5 (4.4%) patients, respectively. Capsule disruption was noted in 11 cases (14.5%), while tumor fragmentation was observed in 7 patients (10.3%). The median time of hospitalization was 3 days (n = 79; IQR 2–4.1). Oral diet was possible from the day after surgery in the majority of patients (n = 34, 68%). The most common complication was dysphagia (n = 5, 4.5%). Conclusions: This systematic review confirms the safety and feasibility of TORS in the treatment of PPS lesions. Given the low quality of included studies, further evidence is needed in order to establish clinical guidelines.

Introduction Parapharyngeal space (PPS) tumors are heterogeneous lesions arising from a complex anatomic area [1]. Benign tumors (particularly pleomorphic adenoma and schwannoma), are the most common histologic subtypes encountered in clinical practice2 and surgery is the mainstay treatment in the majority of cases [2,3]. Within the PPS, the presence of the internal carotid artery (ICA), internal jugular vein, lower cranial nerves (IX-XII) and sympathetic chain leads to several concerns during surgical resection [4,5]. Given the commonly benign nature of PPS tumors, avoiding functional and aesthetic sequelae is mandatory [2,6–8]. A multitude of “external” surgical approaches have been extensively described such as the trans-cervical, trans-parotid and trans-mandibular approach, with the trans-cervical being the most widely used [2,7,8]. Each of the aforementioned surgical techniques are related to different degrees of

negative cosmetic and/or functional outcomes. During the last decades, the trans-oral approach has played a marginal role in the surgery of PPS tumors due to the higher risk of tumor rupture, incomplete removal, and/or unmanageable complications. The narrow surgical space together with limited instrument maneuverability made in the past the trans-oral access a surgical strategy to be adopted only in well selected patients. In 2007, the introduction of trans-oral robotic surgery radically changed the management of PPS tumors [9–13]. The improved fine motor control, in addition to the tremor filter and the magnified 3D vision offered by TORS, leads to a dissection which is more precise than conventional transoral approaches, despite the narrow non-inclined surgical field [14]. A previous systematic review [15], including 44 patients, highlighted the excellent prospects of this surgical approach due to its safety and feasibility in addition to its success rate; since then many more articles have shown the potential role of TORS in the treatment of PPS

⁎ Corresponding author at: Otorhinolaryngology Unit, Humanitas University, Humanitas Clinical and Research Center-IRCCS, Viale Manzoni 56, Rozzano (Mi), Italy. E-mail address: [email protected] (A. De Virgilio).

https://doi.org/10.1016/j.oraloncology.2020.104581 Received 7 December 2019; Received in revised form 6 January 2020; Accepted 20 January 2020 1368-8375/ © 2020 Elsevier Ltd. All rights reserved.

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Fig. 1. PRISMA 2009 flow diagram.

lesions. Therefore, according to the increasing spread of this procedure, we aimed to perform an updated systematic review of PPS tumors managed with TORS, emphasizing the clinical outcomes and analyzing procedure complications as well as the post-operative course of patients.

Selection of studies and eligibility criteria Two independent authors (A.C. and A.D.V.) separately conducted the study searches. All articles were initially screened by title and abstract. Then, studies which were believed to be relevant to our search were downloaded and the full-text manuscripts reviewed to determine eligibility. The conflict between reviewers was resolved by consensus. All studies describing the treatment of PPS tumors with TORS were included. PPS tumors treated with combined surgical approaches including TORS were also included. Clinical studies were excluded if patients were younger than 18 years. In case of studies including data related to several surgical approaches or tumor locations, only data of patients who met the inclusion criteria were extrapolated. If this was not possible, the corresponding studies were excluded.

Methods The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [16]. Data source and study searching A comprehensive electronic search was performed on PubMed/ MEDLINE, Cochrane Library, and Google Scholar databases. Relevant keywords, phrases, and MeSH terms were searched. An example of a search strategy is the one used for PubMed/MEDLINE: “parapharyngeal” OR “parapharynx” AND “robot” OR “robotic surgery” OR “TORS”. The searches in the remaining databases were adjusted to fit the specific requirements. The “cited by” function on Google Scholar was used in order to identify additional articles, and a cross-reference search of the included studies was performed after the electronic search to minimize the risk of omitting relevant data. The last search was performed on November 9, 2019.

Study quality assessment Case series and case report studies are prone to be affected by various types of bias, and no validation tools to assess the methodological quality (risk of bias) are available. Therefore, the modified Newcastle-Ottawa Scale (mNOS) was employed to assess the methodological quality of included studies, as previously performed in several systematic reviews [15–17]. The items related to comparability and adjustment were removed from the Newcastle-Ottawa Scale (NOS) [18] due to absence of comparative studies included in our review. The resulting five items were presented as questions with binary responses 2

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(yes/no) in order to assess the methodological quality. Patient enrollment was considered consecutive only if an explicit statement was found in the manuscript, as suggested by the National Institute for Health and Clinical Excellence (NICE) quality assessment tool [19–21]. The overall risk of bias for each study was considered low (5 criteria), moderate (4 criteria), or high (3 or less criteria) depending on how many criteria were fulfilled. The quality of each study was independently assessed by two authors (A.C. and A.D.V.) and any conflicts were resolved by consensus.

Table 2 Parapharyngeal space tumors histology.

Data synthesis and analysis Given the limited number of patients included in each study and the heterogeneity among these studies, formal meta-analysis could not be appropriately performed. The data from each study was transcribed in tabular form and these were summarized using descriptive statistics. Dichotomous variables were reported as counts and percentages, while continuous variables as mean ± standard deviation, or median ± IQR (interquartile range) if the values were not normally distributed. Results Search results and studies description

Benign tumors

No. of patients (%)

Malignant tumors

No. of patients (%)

Pleomorphic adenoma

66 (58.4%)

4 (3.5%)

Schwannoma

12 (10.6%)

Benign cyst

4 (3.5%)

Benign vascular malformation Lipoma

4 (3.5%)

Ca. ex pleomorphic adenoma Adenoid cystic carcinoma Mucoepidermoid carcinoma Papillary thyroid cancer

Elongated styloid Basal cell adenoma Lymphoepitelial cyst Oncocytoma Cystadenoma Calcified hematoma Brachial cleft cyst Plasmocytoma Myoepithelioma Rhabdomyoma TOT

2 (1.8%) 2 (1.8%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 102 (90.3%)

4 (3.5%)

Metastatic medullary thyroid carcinoma Adenocarcinoma TOT

2 (1.8%) 2 (1.8%) 1 (0.9%) 1 (0.9%) 1 (0.9%) 11 (9.7%)

Fig. 1.

A flow chart of the study identification process is shown in Fig. 1. The search strategy yielded 376 articles after duplicates were removed. After title and abstract review, 336 articles were rejected and full-texts of the remaining 41 papers were obtained and reviewed. Once the inclusion criteria was applied, 22 studies [12,15,22–41] performed between 2007 and 2019 were included in our systematic review (Table 1). Given that a widely accepted definition of case report/case series is not available, we considered a case series if more than 4 patients were enrolled [42]. As a consequence, we included 14 case reports and 8 case series in our review. There were no clinical trials identified in the literature. The reasons behind the exclusions of 19 studies are shown in

Methodological quality of included studies All included studies were case series/reports, which are at the lowest level in the evidence pyramid [43]. The results of risk of bias assessment (mNOS) of included studies are shown in Table 1. The majority of studies, including 69 patients (61.1%), were considered to have a moderate risk of bias (n = 14, 63.6%). Only five (22.7%) and three (13.6%) studies were found to have a low and high risk of bias, including 38 (33.6%) and 4 (3.5%) patients, respectively.

Table 1 Modified Newcastle-Ottawa Scale quality assessment results. Author, year

Question 1

Question 2

Question 3

Question 4

Question 5

Risk of bias

O'Malley, 2007 Desai, 2008 O'Malley, 2010 Arshad, 2012 De Virgilio, 2012 Kim, 2012 Lee, 2012 Park, 2013 Chan, 2014 Ansarin, 2014 Mendelsohn, 2015 Meccariello, 2015 Samoy, 2015 Boyce, 2016 Granell, 2016 Duek, 2017 Chabrillac, 2018 Duek, 2018 Maglione, 2018 Lajud, 2019 Panda, 2019 Chu, 2019

No No No No No No No No No Yes No No No Yes No No Yes Yes Yes No No No

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

No No Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

High High Moderate Moderate Moderate High Moderate Moderate Moderate Low Moderate Moderate Moderate Low Moderate Moderate Low Low Low Moderate Moderate Moderate

Questions 1–5 comprise the tool for risk of bias assessment of case reports and case-series as follows: 1. Did the patient(s) represent the whole case(s) of the medical center? 2. Was the diagnosis correctly made? 3. Were other important diagnoses excluded? 4. Were all important data cited in the report? 5. Was the outcome correctly ascertained? 3

1 (0) 10 (2)

Case report Prospective case series

Case report

Prospective case series

Case report

Case report

Arshad, 2012

De Virgilio, 2012

Kim, 2012

Lee, 2012

4

4 (2)

Case report

Case report

Case report

Mendelsohn, 2014 Meccariello, 2015 Samoy, 2015

Retrospective case series

1 (0)

Case report

Ansarin, 2014

Boyce, 2016

1 (1)

Case report

Chan, 2014

17 (9)

2 (1)

4 (1)

Prospective case series

Park , 2013

11 (5)

2 (2)

2 (2)

10 (8)

3 (3)

1 (1)

Case report

O'Malley, 2007 Desai, 2008 O'Malley, 2010

No. (Male)

Study design

Author, year

Table 3 Systematic review main clinical outcomes.

52 (range 34–66) 61.6 (range 21–80)

54

56

59 (range 40–78) 25 (range 10–31) 42 (range 21–47) 41 (range 34–51) 42 (range 39–45)

57.3 (range 46–68) 39.2 (range 25–56)

68 53.5 (range 31–75)

N/A

Age

TORS (n = 15); TORS-TC (n = 2)

TORS

TORS

TORS

clinical (n = 17): 10.5 (range 0–50); radiologic (n = 7): 18.6 (range 9–31)

14.5 (range 9–24)

N/A

12

6 (range 5–7)

8 (range 1–15)

TORS TORS

17.7 (range 8–42)

8.5 (range 7–10)

TORS TORS

N/A

20 (range 8–33)

4.3 (range 1–6)

1 29.9 (range 12–40)

N/A

Follow-up (months)

TORS (n = 3); TORS with coblation (n = 2); TORS-TP (n = 5) TORS

TORS

TORS TORS (n = 9); TORS-TC (n = 1)

TORS

Surgical appraoch

Pleomorphic adenoma (n = 2); schwannoma (n = 1); angioma (n = 1) Pleomorphic adenoma (n = 11); schwannoma (n = 1); basal cell adenoma (n = 1); mucoepidermoid carcinoma (n = 1); lipoma (n = 1); oncocytoma (n = 1); cavernous hemangioma (n = 1).

Pleomorphic adenoma

Lipoma

Pleomorphic adenoma (n = 2); basal cell adenoma (n = 1); lymphoepitelial cyst (n = 1). Schwannoma

Pleomorphic adenoma (n = 9); elongated styloid (n = 2)

Schwannoma

Pleomorphic adenoma

Lipoma (n = 1); pleomorphic adenoma (n = 1); Adenoid cystic carcinoma (n = 1). Pleomorphic adenoma (n = 8); schwannoma (n = 2)

Benign vascular malformation Pleomorphic adenoma (n = 7); benign cyst (n = 3)

Benign cyst

Pathology

3.8 (range 2.2–7)

4.8 (range 2.9–6.0)

2.5

5.6

Hematoma (n = 1); phlegmon (n = 1); trismus (n = 1).

Radiologic sequela (n = 1)

No

First bite syndrome (n = 1); left vocal cord palsy (n = 1); Horner's syndrome (n = 1) No

No

5.0 (range 4.0–6.0) 3.9 (range 2.9–4.8)

No

No

N/A

No

No

No Pharyngeal deiscence (n = 2).

No

Complications

N/A

5.4 (range 5.0–5.8)

N/A

5.4 (range 3–8.6)

N/A Radiologic 3.5 (range 1.5–5.6); pathologic 3.9 (range 1.5–7.0). 4.1 (range 2.6–6.6)

N/A

Maximal tumour size (cm)

1

N/A

No

N/A

No

4

No

No

N/A

No

No

N/A 1

N/A

Fragmentation

3

2

No

N/A

No

No

No

No

N/A

2

No

N/A 2

N/A

Capsule disruption

N/A

1

N/A

1

1.3 (range 1–2) 1

1

1

N/A

0.66 (range 0–1) 10 (range 5–15)

1 N/A

1

Oral diet

(continued on next page)

1.8 (range 1–7)

3.3 (range 2–5)

3

2

7.5 (range 7–8)

4.3 (range 1–7)

2.6 (range 2–3)

5.5 (range 5–6)

N/A

N/A

0.66 (range 0–1)

2 3.3 (range 1–5)

2

Hospitalization days

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Study design

Case report Case report

Retrospective case series

Retrospective case series

Case report

Case report

Retrospective case series

Retrospective case series

Author, year

Granell, 2016 Duek, 2017

Chabrillac, 2018

Duek, 2018

Maglione, 2018

Lajud, 2019

Panda, 2019

Chu, 2019

Table 3 (continued)

17 (13)

5 (4)

1 (1)

4 (2)

7 (3)

8 (4)

1 (1) 1 (1)

No. (Male)

35 (range 23–63) 51 (range 18–81)

38 (range 23–62) 66

56 (range 35–72) 54.6 (range 30–78)

60 42

Age

TORS (n = 14); TORS-TC (n = 3)

TORS

TORS-TC

TORS

TORS (n = 2); TORS-TC (n = 5)

TORS

TORS TORS-TC

Surgical appraoch

21.9 (range 3–58)

21.6 (range 1–48)

N/A

32 (range 11–42)

N/A

N/A

12 4

Follow-up (months)

Pleomorphic adenoma (n = 7); schwannoma (n = 2); rhabdomyoma (n = 1); brachial cleft cyst (n = 1); myoepithelioma (n = 1); adenoid cystic carcinoma (n = 1); mucoepidermoid carcinoma (n = 1); plasmocytoma (n = 1); papillary thyroid cancer (n = 1); ca. ex pleomorphic adenoma (n = 1).

Metastatic medullary thyroid carcinoma Pleomorphic adenoma (n = 3); schwannoma (n = 2)

Cavernous hemangioma Carcinoma ex pleomorphic adenoma Pleomorphic adenoma (n = 6); cystadenoma (n = 1); calcified hematoma (n = 1). Pleomorphic adenoma (n = 4); carcinoma ex pleomorphic adenoma (n = 2); adenocarcinoma (n = 1) Pleomorphic adenoma (n = 3); lipoma (n = 1)

Pathology

N/A

Radiologic 3.2; pathologic 4 5.4 (range 4.4–7.1)

6.0 (range 5.0–7.2)

N/A

4.4 (range 2.5–6)

N/A 6

Maximal tumour size (cm)

Secondary haemorrhage (n = 1); Horner's syndrome (n = 1) Laryngeal paralysis (n = 1); Horner's syndrome (n = 1); first bite syndrome (n = 1); secondary haemorrhage (n = 1); cervical emphysema (n = 1).

No

Dysphagia (n = 4)

Hematoma (n = 1); dysphagia (n = 1); trismus (n = 1). No

No No

Complications

N/A

1

No

N/A

N/A

N/A

No No

Fragmentation

N/A

1

No

1

N/A

N/A

No No

Capsule disruption

N/A

N/A

2

3 (range 1–5)

4 (range 3–8)

7.5 (range 2–13)

3 3

Hospitalization days

7.6 (range 3–14) N/A

N/A

1

N/A

N/A

1 1

Oral diet

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Patient characteristics

histology consideration. From the literature analysis, emerged a general consensus against the use of TORS in malignant PPS tumors, although it has been proposed for selected malignant lesions when a lateral neck dissection was not needed [35]. In this regard, the data of our review shows that the majority of lesions (n = 102, 90.3%) were benign, while only eleven (9.7%) were malignant. In addition, among benign tumors pleomorphic adenomas was the most frequent (n = 66, 58.4%), followed by Schwannomas (n = 12, 10.6%). TORS is not indicated for the treatment of all PPS tumors, and currently, there are no systematic reviews comparing the different surgical approaches to the PPS. Two relevant papers with more than 1000 cases each have been published [2,3], but there is no data that is able to clarify the specific surgical indications for each approach. In our opinion, the main aspects that should be clarified are: (1) when is TORS alone indicated, (2) when is TORS contraindicated and (3) when should TORS be performed in combination with an open approach. We tried to systematically organize the available data in order to describe the clinical scenarios in which TORS has been used alone or in combination with other approaches. Unfortunately, the majority of included studies did not report whether the tumor was a pure PPS tumor or deep parotid lobe tumor. In fact, distinguishing tumors arising from the pre-styloid or from the post-styloid compartment is crucial for an accurate indication. In addition, we did not find any study that compared TORS to the trans-cervical or any other surgical approaches. As a consequence, the choice of a specific technique and/or approach is nowadays customized to the patient based on the surgeons’ preference and experience [49]. As a general rule, if we exclude vascular malformations, tumors originating from the post-styloid compartment can be, theoretically, resected trans-orally due to the its’ proximity to the oropharyngeal mucosa without the interposition of crucial anatomical structures. However, as reported by Duek et al. [35] and Paderno et al. [47], tumors localized to the upper PPS would be better treated with other approaches such as transparotid-transmandibular or infratemporal fossa approach, apart from some highly selected cases. Doubts on the indication arise in cases of post-styloid PPS tumors which extend into the pre-styloid compartment and tumors originating from the deep lobe of the parotid gland which extend into the poststyloid compartment [50]. The authors opinion, as already reported in a previous paper [25], is that tumors arising from the post-styloid area and extending into the pre-styloid compartment through the stylomandibular tunnel can be resected after tumor cavitation using a debrider [51] or a coblator [25]. The possibility to reduce the dimension of the mass has led to a better control of vascular and neural structures, reducing the risk of morbidities [52]. On the other hand, tumors arising from the parotid gland and extending into the post-styloid compartment should be treated using a combined TORS-trans-cervical/trans-parotid approach. In our systematic review, we collected a total of 18 patients treated with a combined approach. TORS was more commonly associated to a trans-cervical approach (n = 13), while a TORS-trans-parotid combined approach (n = 5) was also described. In particular, the combination of TORS with an open approach was proposed for the removal of large benign tumors, or small lesions arising in the high PPS near the skull base [35]. We emphasize that exact tumor location/origin should be reported in future studies in order to identify the appropriate surgical approach to be adopted in different clinical scenarios and to establish evidencebased guidelines. One limit of this review is the absence of published series with longterm follow-ups. We are now able to assess the immediate post-operative outcomes of TORS, while the long-term results of this procedure could not be evaluated. Although a complete surgical resection was achieved, the risk of disease recurrence could not be quantified, and further studies are needed to clarify this potential issue. In particular, we found a moderate rate of capsule rupture (n = 11, 14.5%) and tumor fragmentation (n = 7, 10.3%), which was lower than the values

The one-hundred and thirteen patients from included studies had a median age of 53.5 (n = 112; IQR 41.5–58.1) and a predominance of male sex (n = 66, 56.9%). The most common tumor diagnosed with histologic assessment was the pleomorphic adenoma (n = 66; 58.4%). The frequencies of all tumors treated are listed in Table 2. The median tumor size measured in 73 patients was 4.8 cm (IQR 3.8–5.4). Surgery and clinical outcomes The main data is summarized in Table 3. All PPS tumors were successfully resected (n = 111, 98.2%). TORS was used for diagnostic purposes in two cases, including a recurrence of mucoepidermoid carcinoma and a papillary thyroid cancer [39]. The majority of patients (n = 93, 83.3%) were treated with TORS alone, while combined transcervical (TORS-TC) and trans-parotid (TORS-TP) approaches were used in 13 (11.5%) and 5 (4.4%) patients, respectively. In the remaining 2 cases (1.8%), TORS was assisted by tumor coblation in order to reduce the volume of the mass. Capsule disruption during tumor dissection was noted in 11 cases (14.5%), while tumor fragmentation was observed in 7 cases (10.3%). Median intraoperative blood loss was 30.45 mL (n = 57; IQR 14.3–95.0). Median robotic setup time was 8.95 min (n = 37; IQR 3.75–13), while median TORS procedure time was 102.5 min (n = 42; IQR 28.5–113.4). The median total surgery time was 147.3 (n = 48; IQR 87.7–175.8). Post-operative course and complications The median hospitalization time was 3 days (n = 79; IQR 2–4.1). Oral diet was possible from the day after surgery in 68% of patients. Delayed oral diet only after removal of nasogastric tube was described in two studies [25,41] at post-operative day 10 (n = 10, 20%) and 7.6 (n = 5, 10%). .Five patients (4.5%) suffered from dysphagia post-operatively, which was the most common complication. Other, less common complications, included hematoma formation/secondary hemorrhage (n = 4, 3.6%), Horner’s syndrome (n = 3, 2.7%), pharyngeal dehiscence (n = 2, 1.8%), trismus (n = 2, 1.8%), first bite syndrome (n = 2, 1.8%), left vocal cord palsy/laryngeal paralysis (n = 2, 1.8%), phlegmon (n = 1, 0.9%) and cervical emphysema (n = 1, 0.9%). The median follow-up was 13.25 (n = 88; IQR 6.5–21.2). Only 1 patient exhibited a radiologic sequela at two year follow-up post removal of a benign vascular malformation. Discussion Although the trans-oral route appears to be the most immediate and least invasive approach to the PPS, it is accompanied by different technical complexities which made it the preferred surgical approach only in very selected cases in the past [44]. The narrow working space and the visual limitations have made the trans-oral approach challenging in the absence of an appropriate technologic platform [45]. The introduction of TORS has indeed revolutionized the surgery of PPS tumors. The use of a magnified 3D surgical field, associated with angled endoscopes and powered instruments with enhanced degrees of freedom, significantly expanded surgical indications [46,47]. This technological refinement potentially reduces the risk for tumor rupture, incomplete removal, and unmanageable complications during the procedure [48]. When indicated, TORS is the approach which best responds to the need of complete surgical excision with low post-operative morbidity [49]. The present systematic review aimed to define the current ‘status of the art’ according to indications, possible complications, post-operative course and follow-up. To date, 22 studies have been published with a total of 113 cases treated. All surgical plans involving neoplastic lesions begins with tumor 6

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reported by a systematic review performed six years ago by Chan et al [15]. This could be interpreted as the effect of a long learning curve in minimizing adverse events. Long-term assessment of these patients is required in order evaluate the real impact of tumor spillage on the recurrence rate. The rarity of PPS tumors is another critical issue in order to formulate general recommendations. In fact, only highly specialized centers are usually involved in PPS tumor management, and therefore the possibility to overestimate the clinical outcomes must be taken into account. Moreover, robotic assistance is usually provided only in tertiary referral centers, commonly in an academic setting, and therefore optimal clinical outcomes and low complications rate could be related to this specific context. Finally, the overall quality of the included studies does not allow for firm conclusions to be made. The majority of studies (77.3%) were considered to have a moderate to high risk of bias. In addition, all studies were case report/series, and no prospective clinical trials are available at this time. Although the rarity of these tumors introduces great difficulty to conducting large cohort prospective studies, further data is still needed in order to clarify the role of TORS in the management of PPS tumors.

[14] [15] [16] [17] [18] [19] [20]

[21] [22]

Conclusions

[23]

This systematic review confirms the safety and feasibility of TORS in the treatment of PPS lesions. All patients were treated successfully and a low rate of complications was observed. Furthermore, the post-operative course of these patients was associated with low morbidity. Although several studies have been published and a great number of patients were successfully treated, the relative low methodological quality of included studies highlights the need of further evidence in order to establish clinical guidelines. Moreover, a comparite study between TORS and other surgical approaches is recommended in order to define specific indications for each established technique.

[24] [25] [26] [27] [28] [29]

Declaration of Competing Interest

[30]

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

[31] [32]

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