Critical appraisal:Henderson MA, Burmeister BH, Ainslie J, Fisher R, Di Iulio J, Smithers BM, et al 2015 3

Risk of bias assessment: Randomised Controlled Trial (Cochrane risk of bias tool)

Random sequence generation

Describe the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

Patients after lymphadenectomy were assigned to either adjuvant therapy or observation only. This was done with a balance between the groups in respect to institution, lymph-node field (parotid and cervical, axilla, or groin). number of involved nodes (≤ 3 vs >3); maximum node diameter (≤4 cm vs 4cms); and extend of extracapsular extension of tumour (none, limited or extensive) by use of minimisation with a random component.

What was the risk of bias from the random sequence generation?

Low

Allocation concealment

Describe the method used to conceal the allocation sequence in sufficient detail to determine whether intervention allocations could have been foreseen in advance of or during, enrolment.

Patients were randomly assigned via a telephone call to the trial Centre.

What was the risk of bias from the allocation concealment?

Low

Blinding

Describe all measures used, if any, to blind outcome assessors from knowledge of which intervention a participant received. Provide any information relating to whether the intended blinding was effective.

Participants, those giving treatment, and those assessing outcomes were not masked to treatment allocation; however at the time of randomisation the identity of the assigned treatment groups was unknown to anyone until assignment.

What was the risk of bias from the blinding of participants and personnel and outcome assessors?

High

Incomplete outcome data

Describe the completeness of outcome data for each main outcome, including attrition and exlusions from the analysis. State whether attrition and exclusions were reported, the numbers in each intervention group (compared with total randomized participants), reasons for attrition/exclusions where reported, and any re-inclusions in analyses performed by the review authors.

Two study populations were analysed in this study, intention-to-treat and eligible population. The reason being that 41 major eligibility infringements were found within 31 patients, and it was suggested that these patients should be excluded from analysis. The only other incomplete data was that of 2 patients, who withdrew their consent after the randomisation process, so they were excluded from analysis but this was reported.

What was the risk of bias from incomplete outcome data?

Low