Background: Maintaining effective cancer screening programmes is crucial for maximising long-term population benefits. While evidence on sustaining public health programmes is growing, empirical research on the sustainability of complex, multi-level, nationally organised programmes such as cancer screening remains limited.

Objectives: We aimed to explore system- and programme-level factors associated with perceived sustainability, used as a pragmatic indicator of sustainability in breast cancer screening programmes in Europe.

Methods: Data were drawn from (i) an online survey of stakeholders who were screening programme coordinators/managers and policy makers in EUCanScreen participating countries, (ii) the European Cancer Organisation’s Cancer Screening Policy Index, and (iii) Eurostat breast cancer screening rates among women aged 50-69 years for 2023. The survey included all 40 items of the Program Sustainability Assessment Tool (PSAT), which encompasses eight domains: funding stability, partnerships, organisational capacity, programme evaluation, communications, strategic planning, environmental support, and programme adaptation. It also included self-ratings of sustainability (1–5, from “very unsustainable” to “very sustainable”) and governance structure effectiveness (1-5, from “very ineffective” to “very effective”), and additional questions on political backing, public feedback/advocacy, and financial oversight. We analysed 29 responses from 26 countries and three regions. Using ordinal probit regression, we estimated associations between perceived sustainability and item- and domain-specific PSAT scores, the Cancer Screening Policy Index, other survey items, and breast cancer screening rates—a potential driver and/or outcome of sustainability. We summarised results according to the Integrated Sustainability Framework domains: outer context, inner context, processes, characteristics of implementers/population, and programme characteristics.

Results: Most programmes were rated as “sustainable” or “very sustainable” (65.5%), while ten (34.5%) were rated as “unsustainable” or "neutral." Perceived sustainability was higher where outer-context conditions were supportive, such as explicit political backing (p=0.01), a consistent financial base (PSAT domain; p=0.01), and higher Cancer Screening Policy Index scores (p=0.04). Indicators of inner context—such as the PSAT organisational capacity domain (p<0.01) and items such as integration of screening into operations and systems, leadership capacity and support, and staff capacity (all p<0.05)—showed positive associations. A more effective governance structure was also associated with greater sustainability (p=0.06). Process-related factors, such as PSAT domains of strategic planning (p<0.01) and programme evaluation (p=0.03) were associated with greater perceived sustainability. Associations with the PSAT domains of environmental support (p=0.33), programme adaptation (p=0.19), and communications (p=0.16), and screening rates (p=0.21) were positive, but with high uncertainty. No association was observed for the PSAT partnership domain (p=0.93).

Conclusions: Our exploratory analysis suggests that programme coordinators’ and policy makers’ perceptions of sustainability in breast cancer screening align strongly with system- and organisation-level conditions—particularly political backing, funding stability, organisational capacity, and planning and evaluation processes. Perceived sustainability is, however, inherently subjective and may not reflect long-term programme sustainment or performance. Future research should incorporate objective sustainment indicators—such as continued coverage and impacts—and examine additional potential determinants related to implementers/populations (e.g., motivation, attitudes) and to the intervention itself (e.g., fit, complexity), as described in the Integrated Sustainability Framework. Advancing this knowledge will improve assessment of cancer screening programme sustainability.