Adherence and patients' experiences with the use of erlotinib in NSCLC treatment: The influence on plasma concentration and the exploration of factors affecting the use in daily practice

Adherence to treatment is a complex and multifaceted issue that can
substantially alter the outcomes of therapy. Variation in plasma concentration
may be due to variability in pharmacokinetics. Even in a clinical trial setting
there is a considerable variability in efficacy and side effects of erlotinib.
In a less controlled environment, like the use of erlotinib in daily practice,
adherence may also play a significant role. Only few studies have focused on
the use of oral anticancer drugs in daily practice and the influence of
adherence to its effectiveness. Information about the reasons for non-adherence
among non-small-cell-lung cancer (NSCLC) patients taking the oral anticancer
drug erlotinib is essential for the development of interventions that may
increase adherence.

Primary Objective: To study the relationship between adherence and the plasma
concentration of erlotinib and to study the relationship between side effects
and adherence to erlotinib in patients with NSCLC.
Secondary Objective: The study is partly of an explorative nature. The
relationships between patient characteristics, disease characteristics, side
effects, quality of life, patients beliefs and attitude towards disease and
medicines, adherence, dose adjustments and plasma concentration of erlotinib in
patients with NSCLC will be studied.

Prospective observational cohort study in which 50 patients starting with
treatment with erlotinib will be followed up until 16 weeks.

Before the start of therapy with erlotinib and during week 2, 4, 8, 12 and 16
patients will be asked to fill in a questionnaire. Furthermore in week 4, 8
and 16 blood samples are collected, which will be analysed for plasma
concentration of erlotinib.