The results confirm that tumour stage influences the risk of recurrence/second primary tumour (SPT). High-risk human papillomavirus (HPV)-infected patients have a significantly higher risk of recurrence/SPT compared with high-risk HPV-negative patients. High alcohol consumption was associated with a higher risk of recurrence/SPT. In this study, the competing risk of death in intercurrent disease (DICD) was given special consideration.
The aim of the present study was to evaluate whether any of the factors which were found to increase the risk of oral and oropharyngeal squamous cell carcinoma (OOSCC) in previous analyses (smoking tobacco, alcohol, high-risk HPV infection, oral hygiene, missing teeth and dentures) have an influence on recurrence or the occurrence of a new SPT of OOSCC within the first 3 years following diagnosis.
One hundred and twenty-eight consecutive cases with planned curative treatment, who were part of a population-based case-control study carried out in southern Sweden between September 2000 and January 2004, were included. Only patients for whom the intention was curative treatment were eligible. The cases were followed to the first event of recurrence/SPT, death, loss to follow-up, 30 June 2005 or a maximum of 3 years. Time to the first event of recurrence/SPT was analysed by cumulative incidence, where DICD was a competing risk. Regression was performed on cause-specific hazard rates.
After a median follow-up time of 22 months (range 0-36 months), 30 recurrences, 2 SPT, 12 lost to follow-up and 21 deaths before recurrence or SPT were observed. Tumour stage was associated with both a higher risk of recurrence/SPT and of DICD. In univariate analysis, patients with tonsillar carcinoma had a significantly higher risk of recurrence/SPT than patients with carcinoma at other sites, but there was no difference according to site in multivariate analyses. High alcohol consumption was associated with a higher risk of recurrence/SPT, but not of DICD. There was no increased risk of recurrence/SPT related to smoking, but there was an association between smoking and DICD. High-risk HPV-positive cases had a higher risk of recurrence/SPT, but a lower risk of DICD compared with high-risk HPV-negative cases. This seemingly higher risk should be interpreted by taking the competing risk of DICD into account.