The prevalence of HPV-positive Oropharyngeal squamous cell carcinoma at one of the largest tertiary care centers in Sub-Saharan Africa Tygerberg Hospital
CONTEXT Limited data on the prevalence of HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) in Sub-Saharan Africa exist. The aim of the current study was to determine the prevalence of HPV-positive OPSCC at one of the largest tertiary care centers in the region (Tygerberg Hospital, Cape Town, South Africa). METHODS Sequential surgical samples of 266 cases of OPSCC diagnosed over a 10-year period (2007-2017) were selected for evaluation and relevant patient characteristics were documented. p16 immunohistochemistry (IHC) was performed as a screening test. All p16 positive cases were further evaluated for HR-HPV using BD onclarity™ HPV assay (BD Diagnostics, Sparks, USA), a real-time PCR assay that detects type-specific E6 and E7 genomic DNA. RESULTS Of 266 OPSCC cases, 14% (n=36) were positive for p16. Of those p16-positive cases, 23 were negative and 13 (13/266=5%) were positive for HR-HPV when evaluated by PCR. P16 was found to have a positive predictive value (PPV) of only 36.1%. HPV subtypes were HPV-16 (n=10), HPV-18 (n=1), HPV-52 (n=1) and HPV-31 (n=1). One case was positive for HPV-16 and HPV-31. HPV-positive OPSCC occurred in 10 men and 3 women (male: female ratio 3.3:1) with a mean age of 51 years (range: 33 to 72 years). All HPV-positive OPSCC arose from the tonsil (n=10) and base of tongue (n=3). Most HPV-positive OPSCC were non-keratinizing (n=10) or partially keratinizing (n=1). In contrast, HPV-negative OPSCC were predominantly keratinizing (n=218). A positive history of smoking was significantly correlated with a negative HPV status (p=0.08) CONCLUSIONS The presence of HR-HPV in 5% of OPSCC cases, in one of the largest tertiary care centers in Sub-Saharan Africa (Tygerberg Hospital), suggests HR-HPV as a minor etiologic agent in OPSCC in this region. Due to its sub-optimal positive predictive value (36.1%), p16 IHC is a less reliable marker for HR-HPV infection due to high incidence of tobacco and alcohol related diseases in this region. When positive, HPV-specific testing should be performed by one of the available platforms. The identification of the less common HR-HPV types; HPV-52 and HPV-31, in our cohort of HPV-positive OPSCC cases, may have implications for in-situ hybridization (ISH) HPV cocktails and current local vaccination strategies.