This investigation was conducted to clarify the long-term effects of lenvatinib on renal function. VEGF is an essential factor for glomerular structure [21], and this study was conducted, supported by the fact that VEGF-R-suppressing agents such as lenvatinib can induce proteinuria [1–3, 4, 6]. Lenvatinib is indicated at present as a monotherapy in patients with radioiodine-refractory DTC [13] and unresectable hepatocellular carcinoma [15]. Further indications are expected [16, 17]. The recommended initiation dose of lenvatinib differs according to the type of malignancy. DTC is a cancer type with a low frequency of liver or renal metastases, which are rarely effecting on drug metabolism and excretion. The results of this investigation could be useful for other malignancies.
Overall, renal function decreased over time to a relatively small degree within 2 years, then declined continuously thereafter. Renal impairment in this study was uniquely defined as a decline in eGFR of > 15 mL/min/1.73 m2 for ≥6 months, with a total decrease of > 20 mL/min/1.73 m2 as of the latest eGFR. Approximately one-third of patients met the definition of renal impairment, confirming that lenvatinib can affect renal function. The international definition of chronic kidney disease (CKD) is a glomerular filtration rate (GFR) < 60 mL/min/1.73 m2, or markers of kidney damage, or both, for ≥3 months, regardless of the underlying cause. Unlike this general definition, a slight eGFR decrease during cancer therapy regardless of baseline eGFR can be detected by our definition. Adopting this definition as a valid indicator for recognizing that eGFR is starting to decline can trigger closer attention to renal function. In this definition, the comparatively acute renal impairment due to end-stage cancer that results in deterioration of whole organs can be differentiated from renal impairment induced by lenvatinib. Conversely, short-term eGFR declines due to lenvatinib cannot be detected in this definition, but such declines are rare. Distinguishing between these two factors is also difficult in patients with end-stage cancer.
The observation period was significantly longer in Group H among the three groups divided by baseline eGFR. The change between baseline and latest eGFR was significantly different in Group H (Fig. 3). Furthermore, no difference in degree of decrease was seen between the three groups at the same time point (Fig. 2, Table 2). That is, the degree of decline in eGFR was unaffected by baseline eGFR. This suggests that no special attention needs to be given to renal function when baseline renal function is acceptably low (e.g., eGFR ≥ 45 but < 60 mL/min/1.73 m2). This also suggests that patients with high renal function have abundant reserve, resulting in an ability to continue treatment for longer. This is supported by the fact that the rate of RECIST-PR and frequency of proteinuria were highest among patients in Group H, and that neither PS at baseline nor renal reason for lenvatinib discontinuation differed significantly between groups. From these assessments, although not definitive, eGFR at baseline is not considered a prognostic predictor as much as a predictor of tolerance for AEs.
When patients were divided into two groups according to the presence or absence of renal impairment, a marked decrease in eGFR was certainly seen after 2 years in Group D. A mild decline was seen even in Group ND, although the degree did not meet the definition (Fig. 4, Table 4). Lenvatinib can thus induce renal impairment in some patients, increasing the potential for deterioration over time. No involvement of DI in the same observation period was seen (Table 5).
Proteinuria was revealed to increase the risk of renal impairment. This may indicate the same phenomenon as the fact that the risk of ESRD increases in a span of > 10 years in healthy subjects with proteinuria, but over a shorter time span. Still, of the 21 patients with grade 3 proteinuria, only 10 patients (47.6%) showed a decrease in eGFR, whereas even among the 19 patients without grade 3 proteinuria, 3 patients (16.0%) showed a decrease in eGFR. Proteinuria may be just one phenotype of renal damage caused by VEGF-R inhibitors, and even patients without proteinuria should be aware of the potential for changes in renal function.
Proteinuria is managed continuously with lenvatinib DI regulation while looking at the balance with disease control. Meanwhile, renal impairment cannot be immediately improved just with regulation of the lenvatinib dose. Once ultimate renal impairment occurs, treatment must be suspended irrespective of successful disease control. Although no patients required initiation of dialysis in this study, eGFR could logically decrease enough to need for dialysis over a long treatment period. The timing of a change to the next treatment line is thus the next important clinical question [8], but that issue cannot be addressed using the present results. Only limited lines of treatment are available for DTC, unlike for some other malignancies. Where multiple treatment options are available, treatment one agent does not need to be prolonged when eGFR is decreasing. Sorafenib, another agent approved for DTC, rarely induces proteinuria [8] and was confirmed as safe by Tatsugami et al., albeit in a 1-year investigation [22, 23]. Dialysis can directly affect quality of life. Ideally, the decision should be made in advance regarding whether dialysis should be initiated when renal function finally fails, in accordance with recommendations from the field of onconephrology [24, 25]. Prolongation of OS with anti-cancer treatment is obviously given very high priority [14], along with consideration of renal prognosis commensurate with the oncological prognosis in patients receiving lenvatinib. The balance between allowed harm and provided benefit from lenvatinib treatment is an important aspect of therapy [14].
Two key limitations to this study should be considered. First, this analysis was limited to Japanese patients. This population reportedly shows a high frequency of proteinuria induced by lenvatinib compared to all subsets including other ethnicities [13, 15, 26]. The smaller number of nephrons may be related to this phenomenon, although the details have yet to be clarified [27]. Ethnicity-specific renal effects of lenvatinib also remain unclear. The second limitation is the lack of consideration given to the muscle mass of each patient. eGFR is an index using serum creatinine level, which is affected by muscle mass. As some patients receiving treatment may have sarcopenia [28], eGFR may be overestimated in cachexic patients.
To the best of our knowledge, this is the first study to describe the long-term efficacy of lenvatinib on renal function in patients with advanced DTC treated with lenvatinib in actual clinical practice.
Our study revealed that lenvatinib can induce renal impairment, especially in treatment periods > 2 years, regardless of baseline eGFR. Lenvatinib can be used safely, at least in terms of renal effects, for periods within 2 years. Patients who start therapy with better renal function have a larger standby capacity, allowing longer clinical application. Grade 3 proteinuria is a risk factor for renal impairment. Decreased eGFR does not necessarily warrant immediate treatment discontinuation, and ideally treatment continuation should be decided according to the balance between allowed harm and provided benefit from lenvatinib.