Second primary tumours after squamous cell carcinoma of the oral cavity

The aim of this study was to determine the incidence, location and timing of second primary tumours (SPT) after diagnosis of oral squamous cell carcinoma (OSCC) and relate the risk of SPT to that after head and neck squamous cell carcinoma (HNSCC) and the risks of those tumours in the general population in order to assess the need for a separate follow-up programme for OSCC patients and to aid development of an evidence-based and individualized follow-up programme for OSCC patients.

All patients diagnosed with OSCC or HNSCC in the Netherlands in 1991-2015 were selected from the Netherlands Cancer Registry. Cumulative incidence rates and Standardized Incidence Ratios (SIR) were calculated. Analyses were stratified by incidence period and age at primary diagnosis of the index tumour, follow-up time, and site of the SPT.

We included 11263 patients with OSCC from a population of 34244 patients with HNSCC, of which the median follow-up time was 4.0 years. OSCC SPT develop in different patterns and at different locations than after HNSCC. The 5-year risk of SPT and SIR (95% confidence intervals) were respectively 0.13 (0.13-0.14) and 3.0 (2.9-3.1) for OSCC. The risk of a SPT was continuous over follow-up time and calendar period but decreased with an increasing age at diagnosis of the index tumour up to the age of 75 and there were differences in sites of SPT.

A specific follow-up protocol for OSCC is needed, which can be individualized on the basis of, among others, age.