Rectal squamous cell carcinoma in immunosuppressed populations: is this a distinct entity from anal cancer?
Published Date:Jan 2 2016
Pubmed Central ID:PMC4703472
Funding:261201000024C/PHS HHS/United States
261201300021I/PHS HHS/United States
5U58/DP003931-02/DP/NCCDPHP CDC HHS/United States
5U58DP000824-04/DP/NCCDPHP CDC HHS/United States
5U58DP003875-01/DP/NCCDPHP CDC HHS/United States
5U58DP003921-03/DP/NCCDPHP CDC HHS/United States
5U62PS001005-05/PS/NCHHSTP CDC HHS/United States
N01-PC-2013-00021/PC/NCI NIH HHS/United States
U58DP000848-04/DP/NCCDPHP CDC HHS/United States
U62PS004001-2/PS/NCHHSTP CDC HHS/United States
U62PS004011-02/PS/NCHHSTP CDC HHS/United States
Z99 CA999999/Intramural NIH HHS/United States
Squamous cell carcinoma (SCC) of the rectum is rare, but as with anal cancer, risk may be increased among immunosuppressed individuals. We assessed risk of rectal SCC in HIV-infected people.
We utilized the HIV/AIDS Cancer Match, a linkage of US HIV and cancer registries (1991–2010), to ascertain cases of anal SCC, rectal SCC, rectal non-SCC, and colon non-SCC. We compared risk in HIV-infected persons to the general population using standardized incidence ratios (SIRs) and evaluated risk factors using Poisson regression. We reviewed cancer registry case notes to confirm site and histology for a subset of cases.
HIV-infected persons had an excess risk of rectal SCC compared to the general population (SIR=28.9; 95%CI 23.2–35.6), similar to the increase for anal SCC (SIR=37.3). Excess rectal SCC risk was most pronounced among HIV-infected men who have sex with men (MSM, SIR=61.2). Risk was not elevated for rectal non-SCC (SIR=0.88) or colon non-SCC (SIR=0.63). Individuals diagnosed with AIDS had higher rectal SCC rates than those with HIV-only (incidence rate ratio=1.86; 95%CI 1.04–3.31). Based on available information, one-third of rectal SCCs were determined to be misclassified anal cancer.
HIV-infected individuals, especially with advanced immunosuppression, appear to have substantially elevated risk for rectal SCC. As for anal SCC, rectal SCC risk was highest in MSM, pointing to involvement of a sexually transmitted infection such as human papillomavirus. Site misclassification was present, and detailed information on tumor location is needed to prove that rectal SCC is a distinct entity.
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