Introduction: The correlation between patient volume and clinical outcomes is well known for various oncological treatments, especially in the surgical field. The current level of centralisation of systemic treatment of (hemato-)oncology indications in Dutch hospitals is unknown. Objectives: The aim of this study was to gain insight in patient volumes per hospital of patients treated with systemic anticancer treatment in the Netherlands. Methods: National claims data (Vektis) of all 73 Dutch hospitals that provide systemic anticancer medication in the Netherlands for the time period 2019 were used. The distribution of volumes of patients treated with anticancer medication for 38 different haematological or oncological indications was analysed. Hospitals were categorized into academic/specialised, general, and top clinical. Two volume cut off points (10 and 30 patients) were used to identify hospitals treating relatively few patients with anticancer medication. Four indications were investigated in more detail. Results: A wide distribution in patient volumes within hospitals was observed. Top clinical hospitals generally treated the most patients per hospital, followed by general and academic/specialised oncology hospitals. The volume cut off points showed that in 19 indications (50%) the majority (>50%) of all hospitals treated less than 10 patients and in 25 indications (66%) the majority of all hospitals treated less than 30 patients with anticancer medication. Four case studies demonstrated that relatively few hospitals treat many patients while many hospitals treat few patients with anticancer medication. Conclusion: In the majority of oncology indications, a large proportion of Dutch hospitals treat small numbers of unique patients with anticancer medication. The high level of fragmentation gives ground for further exploration and discussion on how the organisation of care can support optimization of the efficiency and quality of care. Professional groups, policy makers, patients, and healthcare insurers ...