Research suggests that data from over a quarter of cancer clinical trials may never reach the public domain.

Doctors use the results from trials to choose the best treatment for patients. But experts from the charity expressed concern over the effect inaccessible data has on this process.

They believe a comprehensive database of all clinical trials is needed to monitor the progress of research and ensure that data is published.

"The medical community needs to know the results of clinical trials to be able to view the entire picture of how a treatment works, how it compares to other therapies, and what choices could serve patients best," says Dr. Richard Sullivan, Head of Clinical Programmes at Cancer Research UK.

"It's disturbing to think that important information on clinical trials is being left to gather dust."

One study looked specifically at 500 cancer clinical trials and found that 26 percent had failed to fully publish five years after presenting preliminary data at a leading American cancer conference. Trial investigators cited lack of time and shortage of funds as their main reasons for not publishing.

Another reason some findings remain unpublished is that they may not offer any groundbreaking new results. However, "if only positive results are published this can distort medical literature and leave doctors thinking a treatment is more effective than it actually is," Sullivan notes. "This, in turn, can affect the validity and findings of subsequent reviews, treatment decisions and clinical practice guidelines."