Erlotinib: another candidate for the therapeutic drug monitoring of targeted therapy of cancer? A pharmacokinetic and pharmacodynamic systematic review of literature.

Erlotinib is currently marketed at fixed standard dosage against pancreatic cancer and non-small-cell lung carcinoma. However, erlotinib pharmacokinetics (PK) is characterized by significant variability that may affect efficacy and tolerability. The aim of this review is to assess evidence that would justify therapeutic drug monitoring (TDM) and provide key information for the interpretation of erlotinib plasma concentrations. Literature was systematically reviewed to evaluate the standard criteria defining the potential clinical usefulness of TDM. Assessment was focused on the existence of unpredictable and wide PK variability and of consistent PK-pharmacodynamic relationships. PK parameters actually show marked variability (apparent clearance estimated to 4.85 ± 4.71 L/h, elimination half-life to 21.86 ± 28.35 hours, and apparent volume of distribution to 208 ± 133 L). Many covariates influence these parameters (CYP3A4 inducers or inhibitors, food, age, liver impairment), but most sources of variability still have to be identified. Some studies have demonstrated a relationship between exposure to erlotinib and clinical outcomes or skin toxicity. Erlotinib activity and target concentrations furthermore depend on tumor characteristics (eg, mutations on epidermal growth factor receptor and on K-ras). These results are in favor of TDM in addition to treatment adjustment for tumor biomarkers, but prospective clinical trials validating its clinical benefits are lacking. This review provides all the relevant information available to assist clinical interpretation of erlotinib plasma measurements. PK percentile curves and consideration to covariates yield information on whether a concentration measured is expected, whereas half maximal inhibitory concentration values determined in vitro provide preliminary insights on target concentration values to reach. Eventually, dosage adaptation might be considered in patients with intolerable toxicity because of excessive plasma levels or conversely nonresponse imputable to insufficient exposure.

Gastrointestinal perforations in patients treated with erlotinib: A report of two cases with fatal outcome and literature review.

Erlotinib has been approved as second-line treatment in patients with non-small cell lung cancer (NSCLC) experiencing relapse after first-line platinum-based chemotherapy. Herein, we report two occurrences of erlotinib-associated gastrointestinal perforation (GIP) in NSCLC patients. Two patients aged 60 and 79 years received erlotinib as third- and second-line NSCLC treatment, respectively. GIP occurred following 3 weeks and 6 months of erlotinib treatment, leading to death a few days later in both patients, neither of whom had any intestinal metastasis. Risk factors related to erlotinib-induced GIP were concomitant oral corticosteroid therapy and ciprofloxacin administration, which may result in erlotinib overexposure. GIP is a severe adverse drug reaction of erlotinib, infrequently described in the literature, compared to other targeted therapies. The lethal risk of erlotinib-associated GIP should be taken into account when evaluating the benefit-risk balance of erlotinib in patients without epidermal growth factor receptor activating mutations.