Tumour stage was introduced to the Swedish Cancer Registry in 2004, but this key variable for prognostic research has not yet been validated. We validated the tumour stage data in surgically treated oesophageal cancer patients.
Completeness and accuracy of tumour stage according to the TNM system ("Tumour Node Metastasis") in the Cancer Registry were compared with a cohort study including comprehensive tumour stage data based on the pathological TNM of almost all patients operated for oesophageal cancer in 2006-2010 in Sweden.
Of the 397 patients with pathological TNM data in the comparison cohort, the Cancer Registry reported an overall TNM stage in 390 patients (98.2%), which was based on the pathological TNM of 104 patients (26.2%), the clinical TNM of 183 patients (46.1%), and the pathological or clinical TNM (undefined) of 110 patients (27.7%). The completeness for the separate T, N, and M components was 89.4%, 90.9%, and 85.1%, respectively. The concordance with tumour stage was 98.2%, while it was 51.1%, 70.5%, and 80.4% for the separate T, N, and M components, respectively. While the concordance with tumour stage was high for all TNM assessment groups (98.1-98.4%), the concordance of the T and N components was highest when using pathological TNM (82.7% and 95.2%, respectively), and the concordance of the M component was highest when using clinical TNM (88.5%).
Although the overall completeness of tumour stage is high, the recording of pathological TNM stage and individual components could be improved within the Swedish Cancer Registry.