Assessment of adherence and relative dose intensity with oral chemotherapy in oncology clinical trials at an academic medical center

Background/Aims: Oral chemotherapy is increasingly utilized leaving the patient responsible for self-administering an often complex regimen where adverse effects are common. Non-adherence and reduced relative dose intensity are both associated with poorer outcomes in the community setting but are rarely reported in clinical trials. The purpose of this study is to quantify adherence and relative dose intensity in oncology clinical trials and to determine patient and study related factors that influence adherence and relative dose intensity. Methods: Patients were identified from non-industry-funded clinical trials conducted between 1 January 2009 and 31 March 2013 at the University of Wisconsin Carbone Cancer Center. Data were extracted from primary research records. Descriptive statistics and linear regression modeling was performed using SAS 9.4. Results: A total of 17 clinical trials and 266 subjects were included. Mean adherence was greater than 97% for the first eight cycles. Mean relative dose intensity was less than 90% for the first cycle and declined over time. Male gender, a performance status of 1 or 2, metastatic disease, and traveling more than 90 miles to reach the cancer center were associated with higher relative dose intensity. Conclusions: Patients with cancer enrolled in clinical trials are highly adherent but unlikely to achieve protocol specified relative dose intensity. Given that determining the phase II dose is the primary endpoint of phase I trials, incorporating relative dose intensity into this determination should be considered.