Facultad de Ciencias de la Salud

We describe a clinical case of an 84-year-old man diagnosed with non-small cell lung carcinoma and epidermal growth factor receptor mutation, who was treated with erlotinib, with doses adjusted by therapeutic drug monitoring. This case involved a clearance fluctuation leading to over-therapeutic drug concentrations of erlotinib and toxicity. The intrapatient and interpatient variability of erlotinib, in addition to other factors such as age or variations in liver clearance, create situations that are challenging in clinical practice. During treatment, erlotinib serum concentrations were measured, and the dose was accordingly adjusted. The erlotinib dose required to reduce toxicity (rash grade III) and maintain effective plasma concentrations, as well as clinical and radiological responses, was 50% of the initial dose, underscoring the relevance of therapeutic drug monitoring for tyrosine kinase inhibitors in routine clinical practice.

Introduction: The main goal of treatment in cancer patients is to achieve the highest therapeutic effectiveness with the least iatrogenic toxicity. Tyrosine kinase inhibitors (TKIs) are anticancer oral agents, usually administered at fixed doses, which present high inter- and intraindividual variability due to their pharmacokinetic characteristics. Therapeutic drug monitoring (TDM) can be used to optimize the use of several types of medication. Objective: We evaluated the use of TDM of TKIs in routine clinical practice through studying the variability in exposure to erlotinib, imatinib, lapatinib, and sorafenib and dose adjustment. Materials and methods: We conducted a retrospective analytical study involving patients who received treatment with TKIs, guided by TDM and with subsequent recommendation of dose adjustment. The quantification of the plasma levels of the different drugs was performed using high-performance liquid chromatography (HPLC). The Clinical Research Ethics Committee of the Hospital Quirónsalud Torrevieja approved this study. Results: The inter-individual variability in the first cycle and in the last monitored cycle was 46.2% and 44.0% for erlotinib, 48.9 and 50.8% for imatinib, 60.7% and 56.0% for lapatinib and 89.7% and 72.5% for sorafenib. Relationships between exposure and baseline characteristics for erlotinib, imatinib, lapatinib and sorafenib were not statistically significant for any of the variables evaluated (weight, height, body surface area (BSA), age and sex). Relationships between height (p = 0.021) and BSA (p = 0.022) were statistically significant for sorafenib. No significant relationships were observed between Ctrough and progression-free survival (PFS) or overall survival (OS) for any drug, except in the case of sunitinib (correlation between Ctrough and PFS p = 0.023) in the exposure–efficacy analysis. Conclusions: Erlotinib, imatinib, lapatinib and sorafenib show large inter-individual variability in exposure. TDM entails a significant improvement in exposure and enables more effective and safe use of TKIs in routine clinical practice.

Objective: A review of the literature about the anti-programmed death 1 monoclonal antibody nivolumab permits to verify the existence of several issues still unresolved about their dosing schedule. The aim of the present work was to explore possibilities of nivolumab treatment personalization through therapeutic drug monitoring, in order to improve their effectiveness and efficiency. Method: Observational, prospective study carried out from May 2017 through June 2019 in patients with different tumor diagnoses treated with nivolumab. Blood samples were obtained in the routine clinical practice, once nivolumab steady state was reached. Serum nivolumab levels were determined by means of quantitative ELISA. The standard schedule of 3 mg/kg every two weeks (Q2W) was modified in some patients due to different circumstances, and resulting serum concentrations were compared with those from the non-modified patients and the published data. Results: Blood samples from 19 patients in treatment with nivolumab were analyzed. A total of 39 samples of nivolumab were analyzed between 6th and 27th cycles. The standard schedule of 3 mg/kg every two weeks was modified in 12/19 (60%) patients, with intervals of 3, 4, 5, 6 or 7 weeks, once the steady state was reached. No statistically significant differences were detected when comparing every two weeks and every four week intervals. When the intervals were six or seven weeks, mean plasma concentration showed a statistically significant difference compared with every two weeks. Conclusions: Current data contribute to confirm former suspects about the possibilities of exploring new scenarios to improve and personalize nivolumab dosage. Additional studies to confirm it in bigger series and correlate it with clinical results, and to better define the role of therapeutic drug monitoring in the treatment, are warranted, not only by financial concerns but also for improving quality of life of patients and clinical management aspects. / Objetivo: Una revisión de la literatura sobre nivolumab permite verificar la existencia de diversos aspectos sin resolver sobre su intervalo de dosificación. El objetivo del presente estudio ha sido explorar las posibilidades de personalización del tratamiento con nivolumab mediante la monitorización terapéutica de sus concentraciones séricas para mejorar su efectividad y eficiencia. Método: Estudio observacional, prospectivo, realizado entre mayo de 2017 y junio de 2019 en pacientes tratados con nivolumab que estaban diagnosticados de diferentes tumores. Se obtuvieron muestras de sangre en la práctica clínica habitual, una vez alcanzado el estado de equilibrio de nivolumab. Las concentraciones séricas de nivolumab fueron determinadas mediante ELISA cuantitativo. La pauta posológica habitual de 3 mg/kg cada dos semanas tuvo que ser modificada en algunos pacientes debido a diferentes circunstancias, y las concentraciones séricas resultantes se compararon con las correspondientes a los pacientes en los que no se modificó y con datos publicados. Resultados: Se analizaron muestras de 19 pacientes que recibieron inicialmente 3 mg/kg de nivolumab cada dos semanas. Se analizó un total de 39 muestras, entre los ciclos 6 y 27. La pauta habitual se modificó, una vez alcanzado el estado de equilibrio, en 12/19 (60%) pacientes, en los que se amplió el intervalo a 3, 4, 5, 6 o 7 semanas. No se encontraron diferencias estadísticamente significativas al comparar la maadministración cada dos semanas y cada cuatro semanas. Cuando los intervalos fueron de seis o siete semanas, la concentración sérica media mostró una diferencia estadísticamente significativa en comparación con la administración cada dos semanas. Conclusiones: La información recogida parece confirmar la necesidad de explorar nuevos escenarios para personalizar la dosificación de nivolumab. Se necesitan estudios adicionales en series de mayor tamaño para confirmar esta información, correlacionarla con los resultados clínicos y definir mejor el papel de la monitorización terapéutica, no solo por motivos económicos, sino también para mejorar la calidad de vida de los pacientes y facilitar la administración clínica del tratamiento.