The impact of low iodine diets on people with differentiated thyroid cancer: A mixed methods systematic review protocol

Project Details


Introduction: Around 3,200 people were diagnosed with differentiated thyroid cancer (DTC) in the UK in 2016, and the incidence is rising: it has been estimated that by 2025, the incidence will be 6480[1]. Treatment is usually thyroidectomy followed by radioiodine remnant ablation (RIA). High iodine status may interfere with RIA, and a low iodine diet (LID) prior to RIA may be advised[2].

However, advice in relation to LID is inconsistent both within and between countries [3], and following the diet can be distressing for patients[4, 5]. It is therefore important to gain an understanding of LIDs in relation to DTC treatment, to provide clearer evidence for decision-making.

Methods and analysis:

This review will include qualitative and quantitative studies on LIDs in relation to DTC. Those with a diagnosis of anaplastic or medullary thyroid cancer will be excluded. There will be no language or country of origin restriction imposed and any relevant text that is not written in English will be

translated where possible. The following electronic databases will be searched from their inception: Embase and MEDLINE (via OVID), Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL) via Cochrane Library and CINAHL (via EBSCOhost). Pairs of reviewers will conduct independent screening of titles, abstracts, and full texts, data extraction and risk of bias/quality assessment. The methodological validity for the different study designs will be assessed. We will conduct a narrative synthesis of quantitative studies and a thematic synthesis of qualitative studies if possible. Where there is enough data, we will carry out meta-analysis considering continuous variables as weighted mean differences, and include 95% confidence intervals.

Discussion: This review aims to provide clarity on: the characteristics of LID studied to date (e.g. length, advice); current evidence for the effectiveness (or otherwise) of LID on short and long term thyroid cancer outcomes; the impact of the diet on iodine status; the complications or adverse effects from consuming a LID; adherence to the diet and barriers and facilitators to its consumption.

We will make recommendations for policy makers and practitioners in relation to a LID for the treatment of DTC. Findings are expected to provide clearer guidance for healthcare professionals, which will hopefully translate to less varied practice across the UK. This review will also guide future research in this area and may help the design of a pilot RCT.

PROSPERO registration number: [CRD42020152261]
Effective start/end date1/03/20 → …