Despite clear improvements in patient outcomes, adherence to clinical practice guidelines in the management of rare cancers remains inconsistent across Europe, an analysis jointly conducted by ESMO and EURACAN, the European Reference Network for Rare Cancers (ERN), shows. The results, presented today at the ESMO Sarcoma and Rare Cancers Conference 2026, highlight the opportunity for physicians and public health policy makers to improve outcomes by standardizing and centralizing care for patients with rare malignancies. Together, the number of new cases of rare malignancies exceeds 650,000 per year, representing a quarter (24%) of all cancer diagnoses in Europe each year.
Delayed diagnosis, limited treatment options, and inadequate research make rare cancers difficult to manage and lead to decreased survival rates compared to the broader patient population. The development of comprehensive clinical guidelines for these diseases poses unique challenges due to their low incidence, paucity of evidence from randomized clinical trials, the need for cross-national expertise, and the reliance on retrospective studies, registries, and expert consensus. Nevertheless, cooperation at EU level through the European Reference Network has enabled the establishment of evidence-based standards, including the ESMO-EURACAN clinical practice guidelines in an increasing number of rare disease areas.
A recent study, which formed the basis of the aforementioned analysis, was carried out by EURACAN between September and October 2025 and mapped the actual use of these guidelines across the EURACAN network across 102 specialist healthcare institutions in 25 countries. Uptake was found to be strong overall (over 60%), with most respondents relying on them ‘always’ or ‘often’ across the 10 groups of rare adult solid tumors within EURACAN. However, the primary purpose for which participants reported referring to clinical guidelines was for treatment decision-making, and their use for diagnosis, follow-up care, research, or educational purposes was significantly inconsistent across clinical areas. Use to update other existing guidelines remained limited.
A literature review conducted in parallel with the study further validated these observations and revealed that adherence to expert center guidelines leads to measurable survival benefits, including reduced mortality in uterine and soft tissue sarcomas, improved outcomes in penile cancer, and improved long-term survival in head and neck cancer. This analysis clearly demonstrates how guideline-aligned treatment can significantly improve outcomes across a wide range of rare tumor types by linking consistent evidence-based management to measurable patient benefits.
For ESMO, which is working to expand the development of clinical practice guidelines, this analysis not only confirms the critical importance of clinical guidelines in the management of rare cancers, but also highlights the potential to better serve patients by optimizing the way they are used by physicians and public health decision makers. ”
Professor Jean-Yves Blay (Léon Bérard Center, Lyon, France), Chair of the ESMO Rare Cancer Working Group
“More than just a clinical decision-making tool, clinical practice guidelines can and should serve as quality assurance and standardization measures, research references, and resources for continuously updating best practices, especially important for rare cancers,” he added.
ESMO and EURACAN call on national health authorities to design guideline adherence into treatment pathways and support doctors to provide optimal treatment to patients through the following actions:
- Centralize rare cancer surgery at certified centers
- Enforcing interdisciplinary decision-making and time-sensitive standards throughout patient diagnosis, treatment, and follow-up
- Track adherence to established clinical practice guidelines through a national dashboard
At the European level, ESMO and EURACAN further recommend strengthening ERN-EURACAN as an implementation instrument for equitable access to care in accordance with evidence-based guidelines, which is essential to narrowing survival gaps between rare and common cancers and between EU Member States and delivering on Europe’s plan to beat cancer.
Professor Bray, who was also involved in the analysis, said: “For rare cancers, where clinical expertise and hard evidence are often limited, well-developed guidelines are an important tool to ensure that all patients receive the best possible treatment. “We show that following evidence-based recommendations can significantly improve patient outcomes. This highlights the important role of the Network and the ESMO-EURACAN guidelines in bringing consistency, quality and equity to the management of rare cancers across Europe.” Less than 6 new cases are diagnosed per 100,000 people per year.
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European Society of Medical Oncology (ESMO)
