# Serum Iodine Levels and 8-Year Survival in Patients After Kidney Cancer Diagnosis

## TL;DR

This study found that abnormal serum iodine levels are linked to higher mortality in kidney cancer survivors over 8 years.

## Contribution

The study is the first to investigate the relationship between serum iodine levels and survival in kidney cancer patients.

## Key findings

- Survivors with iodine levels in quartiles III and IV had significantly higher all-cause mortality compared to those in quartile II.
- Higher iodine levels were associated with increased mortality due to kidney cancer progression and non-cancer-related deaths.
- The strongest association was observed in men with iodine levels in quartile IV.

## Abstract

Kidney cancer is among the most common malignancies of the urinary tract. In this prospective study we evaluate the association between serum iodine (I) levels and kidney cancer mortality. We analyzed 284 consecutive, unselected kidney cancer cases and assessed their 8-year survival in relation to I levels. Iodine imbalance, whether due to deficiency or excess, has been associated with adverse physiological effects. Consistent with this, our study demonstrated that serum iodine levels outside the range of 63.42–72.02 µg/L were associated with higher mortality among kidney cancer survivors, mainly driven by progression of the primary malignancy.

Background/Objectives: The aim of this study was to evaluate the association between serum iodine (I) levels and kidney cancer mortality. The role of serum iodine levels in relation to 8-year survival rates in survivors of kidney cancer has not previously been established. In this prospective study, we analyzed 284 consecutive, unselected survivors of kidney cancer and determined their 8-year survival in relation to iodine levels. Methods: Micronutrient levels were measured using inductively coupled plasma mass spectrometry (ICP-MS). Each survivors of kidney cancer was assigned to one of four groups based on the quartile distribution of iodine levels, ranked in ascending order. The multivariable models included covariates such as age at diagnosis, sex, smoking status, type of surgery, histopathological classification and serum levels of selenium, zinc, copper and the zinc-to-copper ratio. Results: We observed that survivors of kidney cancer with serum iodine levels in quartiles III and IV had significantly higher all-cause mortality compared to those in quartile II (reference quartile) (HR = 2.83; p = 0.012; HR = 2.64; p = 0.017). Furthermore, multivariable analysis revealed a significant association between serum iodine levels (quartiles III and IV vs. quartile II) and mortality due to kidney cancer progression (HR = 4.17; p = 0.031; HR = 3.94; p = 0.038, respectively). This association was significant only among men in quartile IV (HR = 16.5; p = 0.027). Additionally a positive association was observed between iodine levels in quartile IV and all-cause mortality from non–kidney cancer–related deaths (HR = 5.41; p = 0.05). Conclusions: To our knowledge, this study is the first investigation of relationship between serum iodine levels and survival of survivors of kidney cancer.