Comparing Human Papillomavirus Prevalence in Rectal and Anal Cancer Using US Cancer Registries, 2014-2015

Rectal squamous cell carcinoma (SCC) is a rare malignancy, and the causal role of human papillomavirus (HPV) in these cancers is thought to be similar to anal cancer. We compared type-specific prevalence of HPV in rectal SCC to anal cancer. In rectal SCC, we evaluated the agreement between HPV prevalence and positivity for p16, a marker of oncogenic activity.

A stratified random sample of rectal SCCs and anal cancers diagnosed between 2014 and 2015 were identified from 3 statewide cancer registries in Iowa, Kentucky, and Louisiana. HPV testing was performed at the HPV laboratory at the Centers for Disease Control and Prevention. HPV types were described using hierarchical attribution to HPV16 and other oncogenic types, weighted for sampling design. In rectal SCC, we computed concordance and Cohen's kappa coefficient (κ) between HPV status and p16 positivity.

A total of 39 rectal and 72 anal cancers were analyzed. HPV16 was the most common type in both rectal and anal cancer and did not differ significantly between sites (71.4% vs 82.1%; P = .32). Concordance between the presence of any HPV type and p16 positivity in rectal SCC was 92% with κ = 0.77.

Rectal SCC and anal cancer have similar type-specific HPV prevalence, with HPV16 found most frequently. Substantial agreement between p16 and HPV status in rectal SCC lends additional support for the etiologic role of HPV in both anal and rectal cancer. Larger studies could be conducted to replicate these findings.