Incidence of human papillomavirus positive tonsillar and base of tongue carcinoma: a stabilisation of an epidemic of viral induced carcinoma?

Aim: To investigate whether the rise during the past decades in the incidence of tonsillar and base of tongue squamous cell carcinoma (TSCC and BOTSCC) and the proportion of human papillomavirus (HPV) positive cancer has continued in Stockholm.

Patients and methods: Pre-treatment biopsies (n=252) available from 280 patients diagnosed with TSCC and BOTSCC during 2008-2012 in the County of Stockholm were tested for HPV DNA by a multiplex bead-based assay. Incidence records were acquired from the Swedish Cancer Registry. The data obtained were evaluated together with previous figures from 1970 to 2007.

Results: HPV DNA was present in 186/252 (74%) of TSCC and BOTSCC biopsies obtained during 2008-2012 in Stockholm. In this region the age-standardised incidence, including the prevalence of HPV-positive and HPV-negative TSCC stabilised 2007-2012 compared to 2000-2006, while for BOTSCC throughout 1998-2012 the same parameters increased moderately (p<0.05, for all). In parallel, from 2000 to 2006 through 2007-2012 in Sweden, the age-standardised incidence of both TSCC and BOTSCC continued to rise (p=0.012 and p=0.001 respectively).

Conclusion: During 2000-2012 the age-standardised incidence and the proportion of HPV-positive TSCC have stabilised at a high level, while the proportion of HPV-negative cancer has remained at a low level in Stockholm, whereas for BOTSCC all parameters are increasing moderately. In contrast, in Sweden the incidence of both TSCC and BOTSCC is still increasing. We hypothesise that the HPV epidemic could be stabilising, first for TSCC, but so far not for BOTSCC, in e.g. some urban areas, while previous trends for both tumours persist at other geographic locations.