Despite a commitment from the pharmaceutical industry in 2014 to improve data transparency, more than half of the trials that led to US approval of anti-cancer medicines over the past decade remained unavailable for independent analysis.

The Flinders University-led research team says the industry's commitment needs revisiting to help restore confidence in evidence-based medicine, and ensure data can be used for further research into the safety and efficacy of drugs.

Published in the journal JAMA Oncology, the study's audit found that of the 304 trials that supported the registration of 115 anti-cancer drugs over the last 10 years, only 136 had individual patient data available for sharing.

For three of the globally top-selling anticancer drugs - nivolumab, pembrolizumab and pomalidomide - 90 per cent of the trial data was unavailable.

In Australia, two of those medicines, nivolumab and pembrolizumab, cost the federal government over $800 million through the Pharmaceutical Benefits Scheme in 2020/21.

Study senior author Ash Hopkins said the most common reason provided for the lack of transparency was the ongoing collection of long-term follow-up data.

"This is the same reason given by Pfizer and Moderna for the clinical trial data on their respective COVID-19 vaccines not currently being available," Dr Hopkins said.

"However, this excuse disregards any commitment to data transparency.

"Ongoing follow-up is of course needed, but it should not hinder the release of the key data that is implicated in the global release of medicines to tens of thousands of people."

The research team has called on the pharmaceutical industry to make data available for independent investigation as soon as drugs are registered.

They said global regulators and governments should also establish mandates for data transparency on all major trials investigating registered medicines.

Australian Associated Press