HIV-Related Anal Cancer: Incidence Rising Despite Effective Antiretroviral Treatment
Abstract & Commentary
By William B. Ershler, MD
Synopsis: Relative to the general population, the risk of anal cancer in HIV-infected patients remains very high. Unlike other malignancies associated with AIDS, effective antiretroviral treatment appears to have no preventive effect on anal cancer, particularly among men who have sex with men.
Source: Piketty C, et al. Incidence of HIV-related anal cancer remains increased despite long-term combined antiretroviral treatment: Results from the French Hospital Database on HIV. J Clin Oncol 2012;30:4360-4366.
The use of combination antiretroviral therapy (cART) to treat HIV infection has led to changes in the causes of death in HIV-infected individuals in industrialized countries.1-3 Over time, the risk that infected individuals will experience other comorbidities has increased. In this context, though the incidence of AIDS-defining malignancies (ADM) has declined, non-AIDS-defining malignancies (nADM) are now an important cause of mortality in HIV-infected individuals. The incidence of several nADMs is higher among HIV-infected individuals than among the general population. Furthermore, unlike what has been observed for ADM, several studies have assessed the standardized incidence ratio of nADM and have shown either no differences or even increased incidence of certain malignancies when comparing rates in the pre-cART era to more recent times.
Anal carcinoma is one nADM for which recent studies have indicated increasing incidence in HIV-infected individuals, particularly after the implementation of cART.4-6 To explore this within the French Hospital Database on HIV, Piketty and colleagues identified 263 cases of invasive anal squamous cell carcinoma confirmed histologically between 1992 and 2008. This nationwide hospital-based cohort includes 69 clinical and academic centers and comprehensive data on close to 110,000 patients with more than 700,000 person-years of risk.
The incidence rates of anal cancer across four calendar periods — 1992-1996 (pre-cART period), 1997-2000 (early cART period), and 2001-2004 and 2005-2008 (recent cART periods) — were determined as well as standardized incidence ratios (SIRs) comparing incidence in various HIV subsets and the general population by using incidence data from the French Network of Cancer Registries.
In HIV-infected patients, the hazard ratio (HR) in the cART periods vs the pre-cART period was 2.5 (95% confidence interval [CI], 1.28-4.98). No difference was observed across the cART calendar periods (HR, 0.9; 95% CI, 0.6-1.3). In 2005-2008, HIV-infected patients compared with the general population had an excess risk of anal cancer, with SIRs of 109.8 (95% CI, 84.6-140.3), 49.2 (95% CI, 33.2-70.3), and 13.1 (95% CI, 6.8-22.8) for men who have sex with men (MSM), other men, and women, respectively. Among patients with CD4 cell counts above 500/uL for at least 2 years, SIRs were 67.5 (95% CI, 41.2-104.3) when the CD4 nadir had been < 200/uL for more than 2 years and 24.5 (95% CI, 17.1-34.1) when the CD4 nadir was always above 200/uL.
These results are consistent with those of prior reports indicating that the risk of invasive anal cancer is increased in HIV-infected individuals, not only in the pre-cART era but more recently as well.6-8 Further, relative to that in the general population, the risk of anal cancer in HIV-infected patients remains extremely high, even in patients with high current CD4 cell counts. cART appears to have no preventive effect on anal cancer, particularly in MSM.
One possible mechanism by which HIV infection would associate with increased rates of malignancy relates to the hypothetical acceleration of constitutional aging processes thought to occur with long-term infection HIV.9 In assessing this, Shiels and colleagues found that age at cancer diagnosis did not differ between HIV-infected patients and the general population for most cancers but notably did for both anal and lung carcinomas. The median age at diagnosis of anal cancer was found to be some 3 years younger in those infected with HIV (42 vs 45 years; P < 0.001).6
Thus, relative to the general population, the risk of anal cancer in HIV-infected patients remains extremely high, even in patients effectively treated with cART. Furthermore, with the aging of those living with HIV, it is likely that the prevalence of this once rare form of cancer will be increasing quite dramatically.
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