Abstracting stage in population-based cancer registries: the example of oral cavity and oropharynx cancers.

Population-based cancer registries (PBCRs) are instruments to provide cancer incidence to promote cancer control and etiological research. A setting of mandatory (standard) variables is routinely collected for patient and tumor. One recommended variable is tumor stage, which supplies information on disease status and is an essential prognostic factor. However, it is not considered as necessary information to be collected by the PBCR. There are studies showing the value of stage as a prognostic variable to evaluate survival, socio-economic status, race and ethnics differences. Our aim is to analyze the feasibility of PBCRs in abstracting TNM for oral cavity and oropharynx. These topographies were selected due to the clinical accessibility of stage tumors by visual inspection and palpation. About 23% of the PBCRs who contributed to CI5-IX indicated their collection of TNM stage for all cancer sites. We analyzed 23,935 cases of oral cavity (OCC) and oropharynx cancer (OPC) from 13 PBCRs. Complete TNM stage for OCC was 52.7% for males and 47.6% for females; for OPC, it was 56% in both genders. Incomplete stage on OCC and OPC ranged from 22 to 25%. Missing was about 18-27% (most common in oral cavity). Missing stage was significantly higher in males for OCC aged > or =70 years, OR 1,64 (1.39-1.94). Our results demonstrate that OPC tend to have more stage, when compared with OCC. Even if it can be diagnosed by visual inspection, these results highlight the fact that information on stage can be a reliable indicator of access to healthcare and diagnosis awareness. Our results demonstrate that is feasible for PBCR to collect stage, although improving completeness of this information needs further technical training and international recommendation to adopt TNM stage as a standard variable for the PBCRs.