The current situation of human papillomavirus (HPV) associated oropharyngeal cancer : a multi-institutional cohort study in Hong Kong

Abstract

Despite the advance in modern oncology, there was limited improvement over the survival outcome of head and neck cancers. Until the discovery of the etiological association between Human Papillomavirus (HPV) and oropharyngeal cancer, an accelerated evolution in the field of head and neck oncology began. This viral-related tumor has ignited tremendous effort in American and European countries to explore the optimal treatment approaches. In contrast, the paucity of comprehensive and robust studies commonly exists in many Chinese and Asian countries. Little is known about the current situation of HPV-associated oropharyngeal squamous cell carcinoma (OPSCC) in Hong Kong.

This retrospective local multi-institutional study attempted to explore the HPV-associated OPSCC in Hong Kong from various aspects, including demographics, risk factors, clinical and histological features, molecular profile, as well as clinical outcomes. Finally, attempts were made to determine any predictive factors to stratify high-risk patients in this distinct disease entity and explore the most appropriate detection algorithm of the biologically active HPV infection in our locality.

With the support from the Hong Kong Cancer Registry and nine public hospitals, 141 (43.3%) of 326 newly diagnosed OPSCC in the whole population of Hong Kong between 2005 and 2009 were recruited. Inclusion criteria were histologically proven OPSCC with tumor specimens available for prospective laboratory tests. Those with non-SCC, non-oropharyngeal in origin and incomplete clinical records were excluded. Prospective HPV PCR and genotyping, and immunohistochemical staining with p16, p53, cyclin D1 and HER-2 were performed. Univariate and multivariate analyses were performed to assess the correlations between various parameters and HPV-associated OPSCC.

Epidemiologically, based on the combined positivity in HPV PCR and p16, the prevalence of HPV-associated OPSCC was 22%. Thirty (96.8%) of thirty one were HPV-16, the remaining one was HPV-18. In the univariate analysis, this cancer directly correlated with female gender (p=0.014), younger age (p=0.012), non-smoker (p=0.02), non-drinker (p=0.06) and early primary tumor (p=0.001). Histologically, basaloid differentiation (p<0.001), non-keratinization (p=0.007) and high tumor infiltrating lymphocyte (TIL) level (p<0.001) showed significant correlations. A distinct molecular profile was identified, with p16 positivity noted in all cases (p<0.001), few of p53 (p<0.001) and cyclin D1 positivity (p<0.001) and absence of HER2 over-expression.

Significantly superior prognosis was demonstrated in HPV-associated OPSCC. The 5-year overall and disease specific survivals were 67.0% and 88.6% compared with 27.8% (p<0.001) and 41.3% (p<0.001) in the non-viral counterpart respectively. Other good prognostic factors identified for OS and DSS included early primary disease (T1/T2) (p=0.02; p=0.001), absence of distant metastasis (both p<0.001), high TIL level (both p<0.001), p16-positivity (p=0.002; p=0.003), non-smoker (p=0.021; p=0.014). In the multivariate analysis, the HPV-associated tumor (HR: 0.28; 95% CI: 0.08 – 0.93; p=0.038), early primary tumor (HR: 0.52; 95% CI 0.30 – 0.89; p=0.017) and absence of distant metastasis (HR=0.15 95% CI: 0.07 – 0.3; p<0.001) were associated with lower risk of death from any causes after controlling other confounding factors.

Most importantly, high TIL level in HPV-associated OPSCC patients was associated with 89% (HR: 0.11; 95% CI: 0.02 – 0.61; p=0.012) lower risk of death from any causes than those with low TIL level, but not present in non-HPV counterpart. In addition, either HPV PCR complemented with typical high-risk genotyping results or p16 IHC positivity complemented with HPC PCR positivity using specific designed primers were two reasonably sensitive and specific detection algorithms based on the local genotypic distribution of this disease.

In summary, this is the first most comprehensive and robust local study indicating the importance of HPV-associated OPSCC in Hong Kong. It successfully illustrated various distinctive characteristics of this viral-related cancer. Additionally, it has suggested a potential predictor to identify the minority with more aggressive diseases and the most effective laboratory detection algorithms in this locality. It definitely facilitates the next step in exploring this disease via larger and prospective trials in coming future.