Determinants of patient screen failures in Phase 1 clinical trials

Certain eligibility criteria for Phase 1 cancer clinical trials may impede successful patient enrollment onto a study. We evaluated patient-specific or study-specific reasons for screen failures on Phase 1 oncology clinical trials and discuss factors which may inhibit subject enrollment.

Thirty-eight Phase 1 clinical trials for solid tumors meeting eligibility criteria and opened for enrollment between February 2006 and February 2011 at one oncology Phase 1 program were examined. Categorical reasons for screen failures and patients' demographics were examined and compared to characteristics of patients that successfully enrolled on a Phase 1 trial.

There were a total of 583 successful Phase 1 enrollment and dose administration events out of 773 Phase 1 consent events (75.4 % dose success rate). The three most common reasons for screen failure were: out of protocol-specified range for chemistry, development of an interval medical issue that precluded proceeding with study participation, and subject declining participation after signing consent. Living further away from the Phase 1 program and receipt of fewer prior lines of systemic chemotherapy were significantly associated with increased screen failures.

Screen failures for Phase 1 studies are not uncommon (24.6 %). When a protocol required tumor or host analyte is not required, most screen failures are due to out of protocol-specified range for chemistry or the development of an interval medical issue. Screen failure rates were increased when patients had longer travel distances and fewer prior lines of systemic chemotherapy.