Exceptional response to everolimus in a novel tuberous sclerosis complex-2 mutation–associated metastatic renal-cell carcinoma

Everolimus, an oral inhibitor of the mammalian target of rapamycin (mTOR) pathway, is currently approved for treatment of advanced renal-cell carcinoma (RCC) after failure of initial treatment with the tyrosine kinase inhibitors. Patients with tuberous sclerosis complex (TSC) syndrome can also develop RCC primarily mediated through mTOR signaling. However, the efficacy and duration of response of mTOR inhibition in patients with TSC-associated RCC is not well known. Herein, we describe a case of a patient with TSC2-associated metastatic RCC with mutations H1620R and Y1650C who has had an exceptional response to everolimus in the frontline setting and continues to derive benefit from mTOR inhibition 2 yr into therapy. Furthermore, the alteration H1620R in exon 37 resulting in a missense mutation is likely deleterious given our findings and previous analyses of the TSC2 gene. Further studies of somatic mutations in extended responders to mTOR inhibitors will help personalize therapy for these patients. It also emphasizes the value of targeted therapies based on genomic analyses.