Men who have sex with men (MSM) who started antiretroviral therapy before highly active antiretroviral therapy (HAART) became available developed invasive anal cancer faster than those who began therapy using HAART, according to a recent Canadian study.
This study, a retrospective analysis of anal cancer cases among MSM in British Columbia, Canada, collected data on 4,937 men who received antiretrovirals between 1988 and 2008.
A little over 34% (1,612) of the study participants identified as MSM. Within that group, 37 biopsy-proven cases of invasive squamous cell carcinoma were diagnosed during the two decades studied. Participants were divided into those who began taking antiretrovirals between 1988 and 1995 (in what is considered the pre-HAART era) and those who did so between 1996 and 2008 (during the HAART era).
The analysis combined a province-wide database of HIV-positive patients with the database of the local anal dysplasia clinic. Patients were more likely to develop anal cancer if they had started taking antiretrovirals before 1996 (P = .002), if their CD4+ cell count dipped below 100 cells/µl (P = .035) and if their CD4+ cell count stayed longer below 100 cells/µl (P = .002).
The 26 anal cancer patients who had started antiretroviral therapy before 1996 correspond to an incidence rate of 370 per 100,000 person-years, compared to an incidence rate of 93 per 100,000 during the HAART era (P < .001; overall incidence rate: 196 per 100,000).
It took an average of 10 years (range: eight to 13 years) from the first recorded CD4+ cell count or viral load to an anal cancer diagnosis. Anal cancer patients started antiretroviral therapy in 1995 on average (range: 1992 to 1997) and took antiretrovirals for an average of seven years (range: five to 10 years) before being diagnosed with cancer in the early 2000s.
About 58% of the cancer patients took their antiretrovirals more than 95% of the time and 49% were virally suppressed when diagnosed with anal cancer. More than 25% of these patients had developed resistance against early types of antiretrovirals (nucleoside reverse transcriptase inhibitors and non-nucleoside reverse transcriptase inhibitors) and 19% were resistant to protease inhibitors. The average lowest CD4+ cell count among those with anal cancer was 70 cells/µl.
"Overall, the current study raises the interesting possibility that HAART may prolong time to development of invasive anal cancer in HIV-positive MSM," the study authors concluded.