Cancer patients struggle with some of the fundamentals of clinical trial design such as randomisation – calling into question their ability to provide informed consent.

According to research presented at the ESMO 2017 Congress, almost all patients (98.3%) considered clinical trials important but they were hazy on the details.

The multi-centre Irish study surveyed more than 1,000 adults with a range of solid and haematological cancers. More than a quarter of patients (27.8%) said they had previously participated in a cancer clinical trial.

More than half of all patients (56.5%) said their doctor would know which treatment arm was ‘better’ and 60.9% had faith their doctor would make sure they received the ‘better’ treatment.

An even higher proportion of patients who had previously taken part in a clinical trial (63.6%) were convinced their doctor would ensure they received the ‘better’ treatment.

Study lead Dr Catherine Kelly, a medical oncologist at Dublin’s Mater Misericordiae University Hospital, said there was a clear need for doctors to ensure patients understood how clinical trials worked.

“Consistent with previous studies, the concepts of chance and randomisation posed difficulties to a significant proportion of patients. Over half of previous medical trial participants and 73% of those who had never been on a cancer clinical trial did not understand that in a randomised trial, the treatment given was decided by chance.”

“We also found that most patients did not understand clinical equipoise: the fact that no one knows which treatment is best. Surprisingly, this was more marked in previous clinical trial participants,” she said.

She added that many patients didn’t realise that clinical trials were not just for when standard treatment had failed.

With low rates of accrual to cancer trials worldwide, better understanding of clinical trials could also help allay fears about participation and improve recruitment, she said.