Outcome measures
The primary outcome of this meta-analysis is the prevalence of occult cervical metastases in primary TBSSC. The secondary outcome is a) to perform a subgroup meta-analysis of the risk of occult metastasis based on the clinical stage of the tumour and b) the rate of occult metastasis in each level in the neck.
Search strategy
This systematic review and meta-analysis were conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist(8). Medline (via Ovid), Cochrane, Embase (via Ovid), Web of Science (Core Collection) and Scopus were searched from inception through to January 2021 (Appendix 1). The research was conducted according to PRISMA criteria. A combination of MeSH terms and free-text words were utilized to search for “temporal bone squamous cell carcinoma” or “temporal bone” or “squamous cell carcinoma” AND “Neck dissection” OR “Elective” OR “Node” OR “Lymphnode” OR “Lymph node” OR “N0”.
The reference lists of articles included in this review as well as narrative reviews published in the last 10 years were also manually searched to minimize the risk of missing data. Two authors (DB and AV) independently screened all titles and abstracts generated by the search and then evaluated the full texts of all the relevant articles identified against the inclusion criteria (Figure 1); a third author (PBR) settled discordances when present.
Selection criteria
Studies were included in the analysis if they met the following criteria:
(a) population study including previously untreated primary squamous cell carcinoma involving the temporal bone
(b) neck staging carried out by performing ultrasound (US) and/or computerized tomography (CT) and/or magnetic resonance imaging (MRI) and/or positron emission tomography (PET)
(c) studies reporting complete or extractable data on the number of patients with cN0 parotid tumours, number of elective neck dissections and cases of occult metastases.
The exclusion criteria were
(a) studies that did not declare precisely how they staged the neck (palpation or imaging) before elective dissection
(b) studies with fewer than 5 patients
(c) non-English language studies
(d) reviews, editorials and letters.
(e) studies containing aggregated and non-extractable data, or duplicated data from previously published work
e) non-squamous cell carcinoma or metastasis
f) recurrent disease.
We defined occult metastases (pN+/cN0) as lateral cervical lymph node metastases identified upon elective neck dissection of patients with clinically uninvolved cervical lymph nodes (cN0) at preoperative staging.