METHODS
Participants and Data Sources
We analyzed data from 13 cohort studies (10 from the United
States and 3 from Canada) that are included in the North
American AIDS Cohort Collaboration on Research and Design
(NA-ACCORD) for the years 1996–2007. Cohorts were included
if they provided data on anal cancers and sexual orientation.
Study methods for NA-ACCORD have been described elsewhere
[15]. Study protocols were approved by the local institutional
review board for each cohort.
Eleven of the 13 participating cohorts were clinic-based, and
data were obtained from medical records. The remaining 2
participating cohorts (Multicenter AIDS Cohort Study [MACS],
and Women’s Interagency HIV Study [WIHS]) were intervalbased,
and data were obtained as part of a research protocol at
scheduled 6-month study visits. All contributing cohorts
used standardized methods of data collection, and submitted
demographic, treatment, clinical, laboratory, and vital status
data on enrolled HIV-infected individuals. In addition, 3
cohorts (MACS, WIHS, and Kaiser Permanente Northern
California [KPNC]) contributed data on HIV-uninfected
individuals. Because sexual orientation was unknown for
the majority of HIV-uninfected individuals, we were unable
to stratify men in the comparison group by MSM status.
Incident anal cancer diagnoses were ascertained separately
by each cohort from medical records, patient interviews
(confirmed by medical record reviews), or linkage with a cancer
registry. Cases comprised all anal cancer diagnoses, regardless
of histology, because histological information was not
provided by all cohorts. Individuals with prevalent anal cancer
were excluded. incidence rates to the reference groups of HIV-uninfected men
and women. For each cohort member, the start of follow-up
(ie, baseline) was defined as the cohort entry date, or 1 January
1996, whichever came last. Individuals were followed until
there was an anal cancer diagnosis, loss to follow-up, death,
or up to 31 December 2007, whichever occurred first.