Abstract 3440: Time and regional incidence trends of human papillomavirus-associated oropharyngeal cancer in Ontario, Canada

Abstract

Abstract Background: Despite the increasing incidence of human papillomavirus (HPV)-associated oropharyngeal cancer (OPC) in the Western World, there are little data describing the change in HPV incidence within Ontario, Canada. We therefore assessed HPV-positivity in a retrospective study of 612 OPC patient samples. Methods: Diagnostic formalin-fixed and paraffin embedded OPC patient samples belonging to two cohorts were retrieved from institutions across Ontario, Canada over two time periods: 1998-1999 (n = 245) and 2003-2004 (n = 367). In all samples, HPV status was assessed initially using p16 immunohistochemistry (IHC). For p16 negative and equivocal staining samples, HPV in situ hybridization (ISH; using an HPV subtype 16/18 probe) was performed as the final indicator for HPV positivity. HPV-positivity rate was then compared over time and geographic region. Results: Overall, p16-positivity was observed in 52.3% (320 of 612) of the OPC patients. For the p16-negative (n = 246) and p16-equivocal (n = 46) samples, 25.3% (n = 74) were positive by HPV16/18 ISH. The HPV infection incidence for the 1998-1999 cohort was 54.3% (133 of 245 samples; 95% CI: 53.9(47.4-60.2)). The HPV infection incidence increased significantly in the 2003-2004 cohort to 71.1% (261 of 367 samples; 95% CI: 71.4(66.5-76.0)) (p<0.0001). When divided based on geographical region, HPV incidence also increased significantly over time (Northern Ontario by 49%, p = 0.04; Eastern Ontario by 23%, p = 0.009; Southern Ontario by 17%, p = 0.009; Central Ontario by 12%, p = 0.05). There were no significant differences between urban and rural areas over the two cohort periods (urban p = 0.8; rural, p = 0.6). Conclusions: HPV-associated OPC increased in incidence in Ontario, Canada, over a 6-year period from 1998 to 2004, which appeared to be applicable across the entire province, regardless of urban or rural regions. A composite HPV detection method using p16 in combination with HPV ISH identified an additional 25% of HPV-positive OPC cases. Citation Format: Wei Shi, Stephen F. Hall, Katrina Rey-McIntyre, Rebecca Griffiths, Wei Xu, Jie Su, Jeff Bruce, Shaohui Huang, Brian O’Sullivan, Kenneth W Yip, Fei-Fei Liu. Time and regional incidence trends of human papillomavirus-associated oropharyngeal cancer in Ontario, Canada. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3440.