Introduction Advanced cancer patients have difficult decisions to make when offered further treatments in clinical trials. It is essential that such decisions are made with a full understanding of the potential impact of further treatment side effects and the trade off against this added symptom burden, and quality of life.

Aims and Methods To present a metasynthesis of findings from three qualitative studies linked to clinical trials exploring patients' motivations, and understandings of the trials. Data from three qualitative studies were synthesised to explore themes associated with participants' motivations when joining a trial and their experiences and understandings of trial processes. The data set comprised interview transcripts from 60+ advanced cancer patients.

Results In retrospect, control arm patients were altruistic and accepting of their allocation, whereas intervention arm patients were more focussed on the potential treatment benefits. Some patients expressed a sense of pressure to do the right thing for family and clinicians. Joining a trial was sometimes seen as the only remaining treatment option. Both groups were pleased to be receiving enhanced care and attention as part of a clinical trial. Patients frequently misunderstood the potential effect of the treatment intervention; some wrongly thought that their treatment was anti cancer, some thought that they may be receiving a placebo when in fact they were on the treatment arm of the trial.

Conclusion The results raise concerns about equipoise in trials, truly informed consent, patients' expectations and experiences of participating trials and the potential impact on their symptom burden and quality of life.