Objective: To review what is known about cancer patients' decisions to enter a phase 1 trial and how they and their relatives perceive the information they receive when they are invited to participate.

Methods: This systematic review is based on the principles of "preferred reporting items for systematic reviews and meta-analyses." A systematic search was performed in the PubMed, Embase, and PsycInfo databases, supplemented by a search for unpublished literature.

Results: We identified 37 studies for inclusion in this review. Patients' decisions to participate in a phase 1 trial were influenced by the drug being tested, information procedures, physician-related factors, and the patient's individual approach to decision making. Patients have difficulties correctly repeating the purpose of a phase 1 trial. In several studies, most patients expressed expectations of personal benefit from participating. Studies performing analyses of the dialog demonstrated that the language of the physicians was incomplete. The relatives' perceptions of such information remain unexplored. Most studies had a comprehensive risk of bias.

Conclusions: Patients' decisions regarding participation in phase 1 trials are based on more than the information of the trial. The way patients express the information they have been given could be limited by the applied methods for evaluating this variable. While relatives are expected to be resources for patients entering a phase 1 trial, this topic has not been investigated.