Are renal tumors associated with lithium treatment?

Abstract

Editorial Zaidan et al. (2014) recently identified solid renal tumors by sonographic scanning among 170 patients in Parisian renal disorder programs who had been treated with lithium for an average of 21.4 years and developed decreased renal function. In such patients, the observed rate of renal tumors was high, at 14/170 (8.24%), and half of the tumors were considered malignant (4.12%). The observed rate of solid renal tumors was nearly six times greater than among patients with chronic renal disease (matched for age, sex, and glomerular filtration rate) but not known to have been exposed to lithium (8.24% vs. 5/340 or 1.47%), and the risk among all observed patients with renal dysfunction (19/510 or 2.73%) was over three times less than with lithium treatment (2.73% vs. 8.24%). These rates were reported to be far greater than in the general population. However, risks among lithium-treated patients without renal impairment were not reported. The report proposes that there is an increased risk of renal tumors in association with long-term exposure to lithium salts among patients with impaired renal function. These striking observations, if validated, are of considerable concern, particularly as long-term treatment with lithium has been associated with risk of pathological and pathophysiological changes in renal function that call for regular, routine clinical monitoring of indices of renal function among patients treated long-term with lithium (Bauer et al. 2006; Baldessarini 2013). Rates of severe impairment of renal function among lithium-treated patients may be as low as 0.5% (McKnight et al. 2012). Given an estimated risk of solid renal tumors of 8.24% (and of malignancies of about 4.12%) of lithium-treated patients with significant renal impairment (Zaidan et al. 2014), a tentative estimate of risk of kidney tumors among all patients exposed to lithium long-term would be approximately 0.041% (0.0824 × 0.005), and of cancers