The Role of Precision Dosing and Therapeutic Drug Monitoring in Precision Oncology: A Single-centre Experience with Everolimus

Purpose Targeted cancer therapies often use a ‘one-size-fits-all’ dosing strategy, despite significant variability in individual drug exposure and its effect on both efficacy and toxicity. Therapeutic drug monitoring (TDM) is a precision dosing method that measures drug levels to guide dosing. This single-centre review investigates the potential benefits of TDM in cancer patients prescribed everolimus. Methods Medical records from Flinders Medical Centre, a public tertiary hospital in South Australia, were retrospectively reviewed for patients treated with everolimus for cancer indications between January 1, 2013, and December 31, 2023. Data on whole blood everolimus concentrations, cancer diagnoses, dosing regimens, survival outcomes and demographics were collected and analysed. Results During the study period, 53 patients with a median age of 64 years (range: 38-85) were treated with everolimus for oncological indications. Diagnoses included metastatic breast cancer (MBC, n = 41), metastatic renal cancer ( n = 6), neuroendocrine tumours ( n = 4) and recurrent ovarian cancer ( n = 2). Among these, 14 patients (26%) underwent at least one everolimus blood level assessment. All MBC patients who underwent TDM-guided dose adjustments avoided treatment discontinuation due to adverse effects. Conclusion Prospective studies are warranted to establish therapeutic ranges and confirm the clinical benefits of TDM in cancer care.