Landmark analysis maps a skewed cancer trials landscape

A review of more than 89,000 cancer clinical trials conducted over two decades has produced what researchers are calling the “most exhaustive” analysis of cancer research to date. The findings expose a trial ecosystem dominated by high-income countries, skewed heavily toward pharmaceutical interventions, and marked by glaring gaps in multinational collaboration and disease coverage.

The volume of cancer trials grew sharply between 2005 and 2021, increasing by a mean rate of 7.3% annually and producing a 207% rise overall. Yet growth plateaued in 2022, likely due to pandemic disruptions and delayed data uploads. Importantly, sheer trial numbers have not translated into proportionate advances in practice-changing evidence.

“Yet the true impact of this effort will depend on translating quantitative growth into methodologically robust studies that are inclusive and clinically relevant,” the authors noted.

The distribution of trials often fails to align with the cancers causing the greatest mortality. Breast cancer and haematological malignancies were overrepresented, while liver, stomach, pancreas and cervical cancers – among the world’s deadliest – consistently ranked low in trial activity. Lung cancer was an exception, with trial representation closely matching its status as the leading cause of cancer deaths worldwide.

The analysis found that 76% of all cancer trials were conducted in high-income nations, with multinational collaboration limited to just 3% of recruiting trials. Phase 2 studies accounted for 39% of all entries, with nearly two-thirds of trials enrolling fewer than 100 patients. Phase 3 studies – critical for regulatory approval and clinical adoption – represented only 13% of the total, a figure that has remained stagnant for more than two decades as focus turns to rare cancer trials and precision medicine.

Pharmaceutical interventions dominate the trials landscape, comprising 61% of all trials. Other treatment modalities remain underrepresented, including surgical procedures (11%), biological interventions such as vaccines and CAR-T therapies (6%), behavioural interventions (3%), radiotherapy (3%), medical devices (3%), and diagnostic tests (1%).

The authors argued that “an overemphasis on pharmaceutical interventions hampers a holistic understanding of and progress in cancer treatment and management. Addressing these imbalances is critical for promoting a more comprehensive and patient-centred approach to cancer research.”

Paediatric oncology represents another stark gap. Only 3.3% of trials included children under 14 years, leaving the distinct needs of this vulnerable population largely unaddressed. Funding is predominantly from non-commercial sources, led by academic and research institutions (54%), followed by healthcare institutions (15%), governments (4%), and non-profits (5%).

Adding to the challenge, underreporting of trial results continues to obscure progress. The median lag from trial registration to publication is 4–6 years, with 30% of trials unpublished even seven years after completion. Such delays impede knowledge translation and highlight the urgent need for standardised reporting.

Finally, global collaboration remains minimal. Only 15% of trials were multinational, and a mere 6% involved partnerships between high-income and low- or middle-income countries. Regulatory fragmentation, funding asymmetries, and logistical hurdles perpetuate this divide, leaving low-resource settings with limited access to the benefits of research.

The authors stress that advancing cancer research requires more than numerical growth. It demands robust, inclusive, and context-sensitive trial designs that reflect diverse patient populations and health systems.

An open-access interactive data dashboard and visualisation of the findings is available at the WHO Global Observatory for Health R&D.

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