Significance of HPV16 Viral Load Testing in Anal Cancer

Human papilloma virus (HPV) is highly frequent among patients with anal squamous cell carcinoma, but the viral load (VL) differs between patients. This study aimed to compare the rate of HPV positivity, HPV16VL, p16(INK4A) and p53 expression between treatment naive and recurrent anal cancer patients. HPV was genotyped via AmpliSens (R) HPV HCR-genotype-titre-FRT kit. HPV16 VL was determined via quantitative polymerase chain reaction-based in-house test. p16(INK4A) and p53 expression was tested via immunohistochemistry. The cohort comprised 13 treatment-naive and 17 recurrent anal SCC patients. High-risk HPV was detected in 87% of cases, and HPV16 (73%) was the predominant genotype. The rate of HPV positivity was higher among women and nonsmokers, and majority of HPV-positive cases were also p16(INK4A)-positive. All p53-negative tumors were HPV16-positive. The most predominant p53 staining pattern in the HPV-positive group was scattered type, whereas it was diffuse type in the HPV-negative group. The HPV16 VL was higher in the treatment-naive group. Further, in the treatment-naive group, cases with scattered staining pattern of p53 had higher HPV16 VL than cases with diffuse staining pattern. The opposite result was noted in the recurrent cancer group. Moreover, p16-positive cases with scattered p53 staining pattern in the treatment naive group had higher HPV16 VL than their counterparts in the recurrent cancer group. In conclusion, the HPV VL, as is the association between VL and p16(INK4A) /p53, is in an inversed trend in treatment naive and recurrent cancer patients, highlighting the importance of HPV VL measurement in anal SCC.