Yuen 2009.

Methods	Location of trial: Hong Kong, China Number of centres: 3 Funding: not stated Trial ID: not stated
Participants	Inclusion criteria: AJCC, Stage I to II, SCC oral tongue; no nodal metastases; no prior surgery, chemotherapy or RT Exclusion criteria: OC of other subsites, or cancer of base of tongue Recruitment period: 1996–2004 Numbers randomised: 72 (all OC: 100% tongue) Numbers analysed: 71
Interventions	Elective selective ND vs therapeutic radical ND Group 1 (n = 36): elective ipsilateral selective ND of level I, II or III neck nodes. Group 2 (n = 36): therapeutic (delayed) dissection. These participants were followed, and received ultrasound examinations every 3 months for the first 3 years. If nodal recurrence was detected, these participants underwent either radical or modified radical ND followed by RT. All participants in the trial had transoral glossectomy with 1.5 resection margins.
Outcomes	Primary: nodal recurrence, disease recurrence, death due to tumour, 5‐year tumour‐specific survival Duration of follow‐up: 34–122 months
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomisation stratified by tumour stage. Method of sequence generation not described.
Allocation concealment (selection bias)	Unclear risk	Used sealed envelopes to contain the allocation. Insufficient information to determine whether allocation was concealed from investigators.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Mortality was primary outcome and considered an objective outcome.
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 participant allocated to observation group was subsequently found to have T3 tumour and was withdrawn. All other randomised participants included in the outcome evaluations.
Selective reporting (reporting bias)	High risk	Reported nodal and local recurrence, DFS and disease‐specific death. No reporting of mortality in each group.
Other bias	Low risk	Groups appeared similar at baseline.

AJCC: American Joint Committee on Cancer; CRT: chemoradiotherapy; CT: computer tomography; DFS: disease‐free survival; DSS: disease‐specific survival; FOM: floor of mouth; HNSCC: head and neck squamous‐cell carcinoma; HR: hazard ratio; MRI: magnetic resonance imaging; MRND: modified radical classical neck dissection; n: number of participants; NCR: neck control rate; ND: neck dissection; OC: oral cancer; OP: oropharyngeal cancer; PET‐CT: positron‐emission tomography–computed tomography; PORT: postoperative radiotherapy; RMT: retromolar trigone; RT: radiotherapy; SCC: squamous‐cell carcinoma; SE: standard error; SOH: supraomohyoid neck dissection.