Impact of low iodine diets on ablation success in differentiated thyroid cancer: A mixed-methods systematic review and meta-analysis.
Study Goal
The researchers aimed to determine if iodine status affects radioactive-iodine treatment success, the effectiveness of low iodine diets (LID) in reducing iodine status, and the impact of LID on patient wellbeing.
Results Summary
The study found that lower iodine status (<50 mcg/L) was associated with greater ablation success compared to higher levels, though evidence certainty was very low. Stricter LIDs reduced iodine status more effectively but did not significantly improve treatment success. LIDs negatively impacted psychological health and were challenging for patients.
Population
Patients undergoing radioactive-iodine treatment (specific condition not detailed).
Effective Dosage
Not specified (focus on iodine status thresholds: <50 mcg/L vs. ≥250 mcg/L).
Duration
1-2 weeks for LID.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
low iodine diet (LID) | decrease | iodine status | - | - | reduces | #1 |
low iodine diet (LID) | increase | ablation success | those with an iodine status of <50 mcg/L (or mcg/gCr) | odds ratio [OR] = 2.63, 95% confidence interval [CI], 1.18-5.86, n = 283 | had greater ablation success | #2 |
low iodine diet (LID) | no change | ablation success | those with an iodine status of <50 mcg/L (or mcg/gCr) compared to 100-199 | OR = 1.59, 95% CI, 0.48-6.15, n = 113 | showed similar rates of ablation success | #3 |
stricter low iodine diet (LID) | no change | ablation success | - | OR = 0.67, 95% CI, 0.26-1.73, n = 256 | had similar rates of success | #4 |
stricter low iodine diet (LID) | decrease | iodine status | - | SMD = -0.40, 95% CI, -0.56 to -0.24, n = 816 | reduced iodine status more | #5 |
low iodine diet (LID) | decrease | iodine status | - | after 1 and 2 weeks | reduction was seen | #6 |
low iodine diet (LID) | decrease | psychological health | patients | - | negative impact | #7 |
BACKGROUND: Debate remains regarding whether to recommend a low iodine diet (LID) before radioactive-iodine treatment and its duration and stringency. This mixed-methods review aimed to determine if iodine status affects treatment success, the most effective diet to reduce iodine status, and how LID impacts wellbeing. METHODS: Five electronic databases were searched until February 2021. An effectiveness synthesis (quantitative studies) and views synthesis (qualitative, survey, and experience-based evidence) were conducted individually and then integrated. Quality assessment was undertaken. RESULTS: Fifty-six quantitative and three qualitative studies were identified. There was greater ablation success for those with an iodine status of <50 mcg/L (or mcg/gCr) compared with ≥250 (odds ratio [OR] = 2.63, 95% confidence interval [CI], 1.18-5.86, n = 283, GRADE certainty of evidence very low). One study compared <50 mcg/L (or mcg/gCr) to 100-199 and showed similar rates of ablation success (OR = 1.59, 95% CI, 0.48-6.15, n = 113; moderate risk of bias). People following a stricter LID before ablation had similar rates of success to a less-strict diet (OR = 0.67, 95% CI, 0.26-1.73, n = 256, GRADE certainty of evidence very low). A stricter LID reduced iodine status more than a less strict (SMD = -0.40, 95% CI, -0.56 to -0.24, n = 816), and reduction was seen after 1 and 2 weeks. The main challenges were a negative impact on psychological health, over restriction, confusion, and difficulty for sub-groups. CONCLUSIONS: Although a LID of 1-2 weeks reduces iodine status, it remains unclear whether iodine status affects treatment success as only a few low-quality studies have examined this. LIDs are challenging for patients. Higher-quality studies are needed to confirm whether a LID is necessary.