European expert consensus on cancer recurrence and progression data collection by population based cancer registries

BACKGROUND: As cancer survival improves, the risk of recurrence and progression (RP) places increasing demands on services. Population based cancer registries (PBCR) recognise the importance of recording these data items and seek defined standardised variables for routine collection of RP events. METHODS: Experts from 14 European countries under direction of the European Network of Cancer Registries (ENCR) defined RP for solid and haematological malignancies, standardised variables and coding formats for PBCRs. A seven-step modified-nominal group technique was used. A survey of RP data recording in 2023, an ENCR workshop in 2023 which included wider representation than from Europe and consultation with all ENCR members followed. RESULTS: Definitions were agreed with a tiered approach to data collection and guidance prepared: Cancer recurrence defined as cancer return after a disease-free period post tumour-reductive treatment (TRT) where cancer had a complete clinical or microscopic treatment response. Cancer progression - an increased disease load post TRT where a verified complete response was not achieved. Transformation where tumour changes from indolent to aggressive is covered in RP definitions. Survey responses indicated 31% of PBCRs collect data on RP for all cancer sites 11% for selected sites. Many identified additional resources, training and better access to clinical data required to collect RP data. Guideline implementation began January 2025 irrespective of primary diagnosis date. CONCLUSION: RP data, standardised and collected by adequately resourced PBCRs, is a key step in quantifying service needs and outcomes of this increasing group of cancer patients. Registries need adequate resources to collect RP data.