Second cancers occurring after cancers of the mouth and pharynx: data from three population-based registries in Australia, Scotland and Slovenia.

Data over at least 20 years from three large population-based registries in Europe and Australasia have been used to assess the risk of second primary tumours occurring after a cancer of the mouth or pharynx. These patients have previously been shown in clinical series to be at a particularly high risk of subsequent tumours, while data from cancer registries have shown conflicting results on the magnitude of the risk. In this study, patients were found to have between a 2-fold (Scotland and New South Wales) and 4-fold (Slovenia) increase in risk of a subsequent tumour over that in the population, although the actual risk in each centre was similar (between 2.8 and 3.1 per 100 person years). The risk remained for 10 years after diagnosis of the original tumour and was primarily in the upper aerodigestive tract. The most elevated risks (approximately 10-fold) were for tumours in the oral cavity and oesophagus. These data provide higher estimates of risk than previously reported from European cancer registries for second primary tumours and emphasize the need for close follow-up of patients who may represent an appropriate population in which to assess possible new chemopreventive agents.