Table 1 Summary of the included studies

1

Vicini et al. (2010) [13]

Italy [da Vinci Robot (Intuitive Surgical Inc., Sunnyvale, CA, USA)]

Retrospective cohort study

10 patients (8 males [80%] and 2 females [10%]) underwent TOR tongue base reduction, with or without additional procedures (Eg: Septoplasty/inferior turbinate reduction/supraglottoplasty/uvulopalatopharyngoplasty/ethmoidectomy)

Patients with OSA-hypopnoea syndrome primarily due to tongue base hypertrophy (OSAHS)

SF-36 Health Survey

The study duration ranged from 3 to 10 months with a mean follow-up period of 6 months

The post-operative polysomnographic results were favourable, with a mean postoperative Apnoea-Hypopnoea Index of 20.6 (± 17.3 SD). Additionally, the functional outcomes related to pain, swallowing, and quality of life yielded promising results. There were rare occurrences of complications

2

Genden et al. (2011) [14]

USA [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Prospective non-randomized case–control study

30 patients (26 males [87%] and 4 females [13%]) with squamous cell CA underwent TORS with or without adjuvant therapy. A comparison group of 26 patients (20 males [77%] and 6 females [23%]) underwent definitive CRT

Base of the tongue CA (11) [37%],

Tonsillar CA (11) [37%],

Oropharyngeal CA (04) [13%],

Soft palate CA (01) [3%],

Retromolar trigone CA (01) [3%],

Laryngeal CA (01) [3%],

Hypopharyngeal CA (01) [3%]

i) Performance Status Scale for Head and Neck Cancer (PSS-HN)

ii) Functional Oral Intake Score (FOIS)

Evaluations were done immediately prior to the treatment and within the post-treatment follow-up care, at 2-week and 3-month intervals for 1 year

Two weeks following treatments, surgical patients exhibited notably improved scores for eating, diet and FOIS compared to the patients who underwent CRT

However, at 3, 6, 9, and 12 months post-treatment, no significant difference was observed in eating, speech, diet, and FOIS between the two cohorts. In the CRT group, diet and FOIS remained lower than baseline at 12 months after treatment. Thus, TORS could be associated with superior functional outcomes compared to primary CRT

3

Sinclair et al. (2011) [15]

UK [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Prospective non-randomized study

42 patients (29 males [69%] and 13 females [31%]) underwent TORS, with or without postoperative adjuvant therapy. 32 patients [76%] underwent postoperative RT and 13 [31%] underwent chemotherapy

Tonsillar CA (29) [69%],

Base of the tongue CA (13) [31%]

M D Anderson Dysphagia Inventory (MDADI) questionnaire

Evaluations were done pre-operatively, immediately post-operatively and at a follow-up visit > 3 months from the surgery. The median postoperative follow-up time was 17 months (ranging from 4–40 months)

Immediately following surgery, average MDADI scores in every domain (global, emotional, physical, and functional) showed a decrease compared to the baseline values. Nonetheless, a consistent and gradual improvement was observed in all domains over time. TORS-assisted resection of oropharyngeal squamous cell CA achieves favourable functional and clinical outcomes. However, some limitations exist in time intervals of data collection and lack of exact control group for comparison

4

Leonhardt et al. (2012) [16]

USA (System not mentioned)

Prospective cohort study

38 patients (28 males [73.7%] and 10 females [26.3%]) underwent treatments under three streams; TORS alone, TORS and RT (22) [57.9%] and TORS and CRT (7) [18.4%]

Oropharyngeal squamous cell carcinoma

i) Short Form (SF-8) Health Survey

ii) Performance Status Scale for Head and Neck Cancer Patients (PSS-HN)

Assessments were done at baseline; prior to the surgery, and at 6 and 12 months of follow-up period

A transient deterioration of a number of QOL domains was noted by 6 months. However, all domains returned to normal levels by 12 months. TORS alone had minimal and temporary effects on speech. Surgery and radiation had fewer adverse effects on QOL than when surgery and CRT were adopted for treatment. Small sample size may limit the ability to generalize the conclusions

5

Chen et al. (2015) [17]

USA [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Retrospective cohort study

31 patients (26 males [84%] and 5 females [16%]) with oropharyngeal CA were treated by trans-oral CO2 laser microsurgery (16) or robotic surgery (15), followed by postoperative RT. Each patient was matched with a patient who had undergone definitive cisplatin-based chemoradiotherapy and was similarly disease-free

Tonsilllar SCC (16) [52],

Base of the tongue SCC (15) [48]

University of Washington Quality of Life (UW-QOL) Instrument

Baseline and 1 year

Out of the functional domains of UW-QUL, a statistical difference was observed between the two groups only in the swallowing domain (p = 0.01). However, the mean global QOL scores at one year in both cohorts did not show any statistically significant difference (p = 0.47). Thus, a similar quality of life could be observed among patients treated by TORS surgery or CRT. Selection bias, varied disease characteristics and management protocol between comparison groups could be possible confounding factors

6

Mercante et al. (2015) [18]

Italy [da Vinci Robot (Intuitive Surgical Inc., Sunnyvale, CA, USA)]

Prospective cohort study

13 patients (6 females [46%]) who underwent TORS with unilateral or bilateral neck dissection without any adjuvant therapy

T1 or T2 base of the tongue CA

i) FEES: Fiberoptic Endoscopic Evaluation of Swallowing

ii) Italian MD Anderson Dysphagia Inventory Questionnaire (MDADI)

iii) Dysphagia Score (DS)

iv) Italian Voice Handicap Index-10 (VHI-10)

Baseline, at 6 months and 12 months postoperatively

Complete recovery of swallowing occurred at 12 months. The speech was unaffected by the surgical intervention while no significant changes were evident in the patient-reported status of swallowing and voice dysfunction, and related QOL after 12-month follow-up. As possible bias; differences in the compared subsets and the disease characteristics could be mentioned

7

Arora et al. (2016) [19]

UK [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Prospective case series

14 patients (13 males [92.9%] and 1 female [7.1%]) underwent tongue base reduction using TORS with or without additional wedge epiglottoplasty. Epiglottoplasty was performed in 10 patients [71.4%]

Patients with OSA not complying with conventional treatments such as continuous positive airway pressure or oral appliances

i) Voice satisfaction using Voice Handicap Index 2 (VHI-2) questionnaire

ii) Swallowing—MD Anderson Dysphagia Inventory (MDADI) questionnaire

iii) Global quality of life—EQ-5D assessment tool system

iv) EQ-VAS

Total duration is four years. Patients were assessed at 2 weeks, 3, 6, 12, 18 and 24 months

Worsening of voice function was observed at the first post-operative day and 2 weeks following surgery (p < 0.05). However, the mean score gained the baseline levels by 3 months. The same patterns were observed in swallowing function. The overall QOL was improved in all patients from 3 months onwards. Therefore, TORS of the tongue base with or without epiglottoplasty seems a considerable treatment option for selected patients with OSA. As limitations, small sample size, lack of control group, selection bias and performance bias have been stated

8

Ling et al. (2016) [20]

USA (System not mentioned)

Retrospective observational comparison cohort study

138 patients (115 males and 23 females) who underwent primary TORS with or without adjuvant (chemo)radiotherapy (92) or definitive CRT (46)

Tongue base CA (67),

Tonsillar CA (58),

Pharyngeal wall CA (4),

Soft palate CA (2),

Unknown primary (7)

University of Washington Quality of Life—Version 4 (UW-QOL V4) questionnaire

The assessments were done at 1, 6, 12, and 24 months from the completion of TORS or definitive CRT

Patients who underwent definitive TORS experienced notably improved long-term outcomes in the saliva domain. Among patients who received adjuvant therapy, QOL declined in both the saliva and taste domains. Adjuvant therapy was also linked to poorer scores in terms of appearance and recreation at 6 months, speech at 12 and 24 months, and chewing and swallowing at 24 months. Compared to surgery combined with adjuvant therapy, definitive CRT resulted in poorer QOL related to saliva at 1 month and reduced QOL related to chewing at 12 months. However, it is worth noting the significant difference in disease staging between the two groups. Also small sample size and selection bias could have contributed to the outcome

9

Ozbay et al. (2017) [21]

USA [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Prospective cohort study

29 patients (27 males [93.1%] and 2 females [6.8%]) underwent TORS and unilateral neck dissection with postoperative RT (13) [44.8%] or postoperative CRT (16) [55.1%]. Among them, 27 (96.4%) were HPV positive

Tonsillar CA (17) [58.6%],

Tongue base CA (7) [24.1%],

Occult primary (5) [17.2%]

Head and Neck Cancer Inventory (HNCI)

Evaluations were done at baseline preoperatively and at 3 weeks, 3 months, 6 months, and 12 months postoperatively

Compared to the initial baseline values, at three weeks, QOL declined significantly in the eating and speech domains. At three months, these reductions were more significant in all five domains. At six months, improvements were observed only in the speech and aesthetics domains, while other domains and the overall QOL continued to demonstrate reductions. However, at 12 months, all domains showcased enhancements, except for speech and aesthetics domains which showed a return to the baseline level. As possible bias factors; small sample size, lack of long-term follow up data and the absence of non-surgical comparison arm could be highlighted

10

Achim et al. (2018) [22]

USA [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Prospective longitudinal cohort study

74 patients (68 males [92%]) underwent partial pharyngectomy or hemiglossectomy via TORS with concomitant neck dissection. Adjuvant CRT was administered for tumours having positive margins and extra-nodal extension while adjuvant RT was given for tumours with perineural invasion, lymphovascular invasion, or pN2a or greater disease. Therefore, the comparisons were done between the groups of patients undergoing TORS only and TORS and adjuvant radiotherapy (TORS + RT) or TORS and chemoradiotherapy (TORS + CRT)

Tonsillar CA (42) [57%], Base of the tongue CA (31) [42%] and carcinoma of unknown primary (1) [1%]

i) Eating Assessment Tool (EAT-10)

ii) University of Michigan Head and Neck Quality of Life (HNQOL) Instrument

Collected at baseline, postoperatively between 7–21 days, at 6–12 months intervals and long-term follow-up (> 12 months). The median long-term follow-up was 21 months. For short-term follow-up, the records were taken from 65 patients (88%) while for the long-term follow up only 64 patients (86%) were included

Compared with patients who underwent adjuvant therapy, patients who underwent surgery alone experienced better functional outcomes, especially related to swallowing and speech, with QOL measurements returning to near baseline. However, the study also highlights several limitations such as broad time points for follow up, possible variations in nature and extent of the primary disease, in providing adjuvant therapy and possibility to attend for follow up care due to the coverage of wide geographic area

11

Gallitto et al. (2019) [23]

USA (System not mentioned)

Retrospective cohort study

46 patients (44 males [95.7%] and 2 females [4.4%]) underwent TORS (including unilateral or bilateral neck dissection) with unilateral neck RT (9) or bilateral neck RT (37). 17% of the patients received adjuvant CRT

Two major cohorts were compared in this study:

i) Patients who were treated with trimodality therapy (surgery + chemotherapy + RT) with bilateral neck radiation,

Patients treated with trimodality therapy with ipsilateral neck radiation, sparing the contralateral side

Base of the tongue CA (19) [42.4%],

Tonsillar CA (26) [57.8%]

University of Washington Quality of Life (UW-QOL) Questionnaire

Within the first 6 months and after 1 year following completion of chemoradiation therapy

There was no statistically significant difference in overall survival between the two groups. However, unilateral neck radiation was associated with better patient-reported outcomes in salivary function, mood, and anxiety

HPV + node-positive T1-T2 non-well-lateralized tonsil or tongue base cancers represent ideal candidates for primary robotic surgery with bilateral neck dissection to identify those who need ipsilateral radiation, by sparing the contralateral neck, since unilateral neck radiation with concurrent chemotherapy provides superior QOL and comparable survival to those undergoing bilateral neck radiation with concurrent chemotherapy. As a major limitation, lack of balance between patients receiving unilateral and bilateral neck RT could be highlighted

12

Lazarus et al. (2019) [24]

USA (System not mentioned)

Prospective cohort study

10 patients (5 males and 5 females) underwent TORS with (9) or without (1) neck dissection. Five patients underwent adjuvant RT. Chemotherapy was not administered to any of the patients

Base of the tongue CA (5),

Tonsillar CA (5)

i) MD Anderson Dysphagia Inventory (MDADI)

ii) Performance Status Scale (PSS)

Baseline and at 1 month post-operatively

All the patients showed a normal level of swallowing function, ability to eat in public, ability to take a normal diet, normal range of tongue motion and optimal understandability of speech by 1-month post-surgically. However, the small sample size may have led to errors such as selection bias, sampling errors and insufficient power

13

Di Luca et al. (2020) [25]

Italy [da Vinci surgical system (Intuitive Surgical, Sunnyvale, CA, USA)]

Retrospective cohort study

84 patients (16 females [19%] and 68 males [81%]) with recurrent lingual tonsillitis were treated with a lingual tonsil resection using trans-oral robotic surgery. Among them, a cohort of 60 (71.4%) patients was subjected to an assessment of their quality of life after surgery and post-operative dysphagia

Recurrent lingual tonsillitis

i) Glasgow Benefit Inventory (GBI)

ii) MD Anderson Dysphagia Inventory (MDADI) questionnaire

The mean clinical follow-up time ranged from 49.6 ± 27.1 months (range 6–109 months)

In GBI, the domains of general, Social and Physical showed mean values of + 49.5 ± 21.5, + 28.8 ± 20.3, and + 65.8 ± 32.1 respectively

The average composite MDADI score showed an optimal level of swallowing

TORS provides a promising treatment option for recurrent lingual tonsillitis providing improved QoL and swallowing function

14

Xu et al. (2020) [26]

USA (System not mentioned)

Retrospective cohort study

76 patients (62 males [81.6%] and 14 females [18.4%]) with Human papillomavirus–associated oropharynx squamous cell carcinoma who underwent surgery alone (17), surgery with adjuvant (chemo)radiation [S-a (C)XRT] (23), and definitive (chemo)radiation [d (C)XRT] (36)

Tonsillar CA (44) [57.9%],

base of the tongue CA (27) [35.5%],

Pharyngeal wall CA (1) [1.3%],

Soft palate CA (1) [1.3%],

Unknown primary (3) [4%]

All were HPV-associated stage 1 OPSCC

i) University of Washington Quality of Life (UW-QOL) version 4

ii) European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core Module (EORTC QLQ-C30) version 3.0 and its head and neck-specific module (EORTC QLQ-HN35)

iii) University of Michigan Xerostomia Questionnaire (XQ)

iv) Neck Dissection Impairment Index (NDII)

Median follow-up time of 2.2 years. The participants responded to the questionnaire at different time intervals

Most of the patients perceived their post-treatment overall health-related QOL as good or better, showing statistical equivalence across treatment groups. Better salivary/taste/oral functions and less pain, oral/dental, sexual and financial problems were reported in patients who underwent surgery alone compared to d(C)XRT and S-a(C)XRT patients. S-a(C)XRT patients encountered more problems associated with appearance and cough, compared to d(C)XRT patients. No statistically significant differences in neck or shoulder functions were found between surgical and non-surgical patients

However, post-treatment QOL for early-stage HPV + oropharyngeal squamous cell carcinoma patients is usually high regardless of the treatment modality. The differences between S-a(C)XRT and d(C)XRT cohorts are subtle/may be due to other factors. Moreover, it is important to note the limitations in a retrospective study

15

Lee et al. (2022) [27]

USA (System not mentioned)

Retrospective cross-sectional study

37 patients (35 males [94.6%] and 2 females [5.4%]) with HPV + , Oropharyngeal squamous cell CA who underwent neoadjuvant chemotherapy followed by TORS at least 2 years before the study

Tonsillar CA (16) [43.2%],

Base of the tongue CA (20) [54.1%],

Soft palate CA (1) [2.7%]

All cases were HPV + 

i) MD Anderson Dysphagia Inventory Questionnaire (MDADI)

ii) Functional Oral Intake Score (FOIS)

Median of 3.8 years post-treatment (interquartile range, 2.0–8.6 years)

78.4% (n = 29) of patients who were treated with neoadjuvant chemotherapy and TORS achieved optimal long-term swallowing function (MDADI > 80) with a near-normal median MDADI composite score of 98.9. A majority of the patients tolerated total oral intake without restrictions

Patients with oropharyngeal squamous cell carcinoma treated with neoadjuvant chemotherapy and TORS may achieve favourable long-term swallowing outcomes, by preventing post-operative radiotherapy. Nevertheless, the pre-treatment MDADI scores were not available to detect the precision changes in the swallowing function

16

Price et al. (2022) [28]

USA (System not mentioned)

Prospective cohort study

79 patients (71 males [89.9%] and 8 females) with Oropharyngeal CA. All underwent surgery (94.9% TORS) with adjuvant CRT under two different regimes. [Cohort A—30 Gy in 1.5-Gy fractions twice a day over 2 weeks with weekly docetaxel (15 mg/m2) if they had intermediate pathological risk factors,

Cohort B—36 Gy in 1.8-Gy fractions twice a day over 2 weeks with the same chemotherapy regime if they had extra-nodal extension]

Tongue base CA [41.8%],

CA involving tongue base and other areas [5.1%],

Tonsillar CA [39.2%],

CA involving tonsil and other areas [1.3%],

CA involving tonsil and soft palate [1.3%],

Tonsil and tongue base CA [11.4%]

All were HPV + cases

i) European Quality of Life (Eq-5D)

ii) Functional Assessment of Cancer Therapy − Head and Neck Version 4 (FACT-H&N)

iii) European Organisation for Research and Treatment of Cancer Head and Neck 35 (EORTC H&N 35)

iv) The University of Michigan Xerostomia-related QOL Scale (XeQOLS)

Baseline measurements were taken post-surgically prior to initiating adjuvant radiotherapy (RT) and at 1, 3, 12 and 24 months post-RT

Compared with the baseline levels, both cohorts did not show any significant difference in all the QOL measurements at 12 months. All the assessment tools showed an improvement in QOL and most patients returned to baseline level of function and QOL. Excellent swallow outcomes were maintained with the preservation of global and xerostomia-related QOL. Nevertheless, the study also discusses the possible impact of lack of pre-surgical data on swallowing function and QoL on the overall interpretation

17

Salmon et al. (2022) [29]

USA (System not mentioned)

Prospective cohort study

09 participants (07 males and 02 females) underwent tongue base hemi-resection with or without adjuvant therapy. 04 participants underwent TOR alone while 04 participants underwent adjuvant RT. 02 patients underwent adjuvant chemotherapy, out of which one patient underwent both chemotherapy and RT

Tongue base CA

i) Eating Assessment Tool (EAT-10)

ii) Functional Oral Intake Score (FOIS)

At the Baseline and post-operatively at one-week, four-week and 12-week intervals

The scores worsened by 1 week post-operatively but improved within the 4-week and 12-week intervals. Similarly, FOIS had a significant difference with the week 1 evaluation and there were no significant differences with week 4 and 12. Therefore, TORS could make changes in the swallowing-related QOL, and oral intake in the immediate postoperative phase. As limitations of the study followings have been stated: Small sample size, the effect of other confounding factors on functional outcomes, absence of constant follow up for patients with newly diagnosed base of the tongue CA during the preoperative time frame, loss of follow up cases

18

Scott et al. (2022) [30]

Denmark (System not mentioned)

Prospective longitudinal cohort study

44 patients (33 males [75%] and 11 females [25%]), aged 18 years or older, with the following characteristics were included;

World Health Organization (WHO) performance stage of 0–2,

no evidence of distant metastasis,

no previous history of head and neck cancer or RT in the head and neck region

31 patients underwent TORS alone while 13 patients underwent only RT

OPC involving the palatine tonsils (30) [68%], the base of the tongue (11) [25%] and the soft palate (3) [7%]

i) European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core (EORTC QLQ-C30)

ii) European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core-Head & Neck Module (EORTC QLQ-H&N35)

iii) MD Anderson Dysphagia Inventory questionnaire (MDADI)

At baseline, 1 year follow up and 3 years follow up

Although both cohorts showed improvement in swallowing function after one year, the TORS group showed a higher mean composite MDADI score at 3 years compared to the baseline level

In the EORTC-C30, the only statistically significant difference between 1- and 3-year scores was an improvement in the physical subscale of 8.6 (p = 0.037) for patients treated with RT. It is important to note the differences in the disease characteristics and the management protocols for the comparison groups in this study