National and international variation in the registration of bladder cancer.

OBJECTIVE: To determine whether variations exist in the methods by which different cancer registries record information on bladder cancers.
METHODS: The registration practices of the various cancer registries within the UK, Europe and the USA were investigated by consulting the available publications and by correspondence with registry staff. In addition, a telephone survey was carried out within the UK to determine whether the national guidelines on bladder cancer coding were being followed.
RESULTS: There is variation in the registration of bladder cancers both among regions within the UK and between the UK and other regions. The telephone survey showed that only four of the 11 UK regional registries were correctly following the national bladder cancer coding guidelines. Bladder cancer registration also varies between the cancer registries within mainland Europe. When comparing registration practices in the UK and the USA the major difference is that cases of bladder carcinoma in situ and pTa transitional cell carcinoma are included in the North American cancer statistics but not in the British cancer statistics.
CONCLUSION: Much needs to be done before it can be claimed that the registration of bladder cancers has been standardized either nationally or internationally. In particular, the differences in registration practices between the UK and the USA will tend to give a falsely low impression of British incidence and survival rates compared with the equivalent North American figures. This confounding factor must be considered if these incidence and survival values are to be compared.