Metastatic (HR-positive, HER2-negative) breast cancer (BC), advanced or unresectable neuroendocrine tumours of pancreatic (pNET), gastrointestinal or lung origin and metastatic renal cell carcinoma (mRCC) are diseases with poor outcome. Everolimus increases patients' median progression-free survival (PFS) with 4.6 months in metastatic BC (mBC), 7 months in (p)NET and 3 months in mRCC. However, serious adverse events (AEs) occur frequently. This reduces effectiveness of everolimus, because AEs are managed with dose reductions, treatment interruptions or even complete discontinuation of everolimus. Therapeutic-drug-monitoring (TDM) is used to adjust the prescribed daily dose, to maintain effective everolimus whole blood concentrations, with the lowest possible risk of AEs. While everolimus TDM has been common in transplantation medicine, it has not been implemented in oncology. The importance of TDM in oncology is supported by previous research which showed that a 2-fold increased everolimus whole blood trough concentration was associated with a short-term risk of grade ≥ 3 pneumonitis, stomatitis and metabolic events. Moreover, an exposure-toxicity relationship of everolimus in patients with thyroid cancer was observed, since initial everolimus concentrations could be associated with early toxicity (\< 12 weeks, e.g. stomatitis). However, the association between initial everolimus measurements and long-term AEs (≥12 weeks, e.g. pneumonitis, anorexia and anemia) of any grade and the need for everolimus dose reductions could not be made. Since levels ±\>18 µg/L were associated with toxicity, the investigators assume that the upper therapeutic window of everolimus in the oncologic setting will be ±18 µg/L. Similarly, a tendency to improved PFS and overall survival was observed when Cmin in steady state was above 14.1 μg/L. This seems to be the lower limit of the therapeutic window. Before consensus about the feasibility of everolimus TDM in the oncologic setting can be achieved, a number of questions (the knowledge gaps) need to be answered: 1. It is unknown whether everolimus whole blood trough levels (over time) predict long-term AEs. 2. The optimal concentration range for everolimus, with the treatment of mBC, mRCC, or (p)NET is unknown, especially the upper limit associated with toxicity. 3. It is unknown what everolimus concentration level is associated with the need for everolimus dose reductions.
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Everolimus TDM to predict long-term toxicity
Timeframe: Up to 2 year