Appendix.

Algorithm for bladder cancer staging according to TNM classification in the Danish Cancer Registry

Stage	TNM codes
Localized	Ta, is, 1–4, x N0 M0
	Ta, is, 1–2 N0 Mx
	Ta, is, 1 Nx M0, Mx
Regional	Ta, is, 1–4, x N1–3 M0
Distant	Ta, is, 1–4, x N1–3 M1
	Ta, is, 1–4, x N0 M1
	Ta, is, 1–4, x Nx M1
Unknown	T2–4, x Nx M0,x
	T3–4, x N0 Mx
	T1–4, x N1–3 Mx
	T0 N0–3, x M0, 1, x

Notes: Ta and Tis apply to noninvasive bladder cancers, however, they are included in the algorithm, due to the possibility of misclassification. T0 denotes cancer of unknown primary localization, only included in the unknown category, again due to possible misclassification. In our material, only four patients were registered with a T0 code.

Abbreviation: TNM, tumor, node, and metastasis.