ANAL CANCER AND HIV
(How Are They Connected)
(How Are They Connected)
Rising rates of anal cancer among men in the USA have been heavily influenced by the HIV epidemic since the 1980s, a study shows.
However, the authors found that while rates of anal cancer are higher in women than men, and have also increased during the same period, HIV infection has not significantly contributed to this.
Meredith Shiels (National Cancer Institute, Rockville, Maryland) and colleagues used data collected between 1980 and 2005 from the HIV/AIDS Cancer Match (HACM) Study, which incorporates 17 HIV/AIDS and cancer registries. During this time there were 20,533 anal cancer cases, of which 1665 (8.1%) occurred in HIV-infected patients.
Between 1980 and 1984 and 2001 and 2005, the incidence of anal cancer rose from 0.44 to 0.93 cases per 100,000 men and the proportion of anal cancers in HIV-positive men rose from 1.1% to 28.4%. Overall, 83.5% of HIV-infected anal cancer cases were in men who have sex with men.
Rates of anal cancer also increased in women. The authors estimated that between 1980 and 1984 and 2001 and 2005 the incidence of anal cancer rose from 0.68 to 1.29 per 100,000 years, and the proportion of anal cancer among HIV-positive women rose from 0% to 1.2%.
Shiels and colleagues found that while HIV-infected anal cancer cases strongly influenced the overall trend in incidence in men, exclusion of HIV-related cases had no effect on the increase in incidence rate in women.
While anal cancer is rare in the USA, it is the fourth most common cancer among HIV-infected individuals. The authors say that the association is likely to be related to anal human papillomavirus (HPV) infection, which is transmitted during anal sex. HIV-related immunosuppression may also impair the immune response to HPV infection, making HIV-infected individuals more susceptible to anal cancer.
They say that their findings could influence potential public health strategies such as HPV vaccination or Papanicolaou testing.
"Measures that would effectively prevent anal cancer in HIV-infected males could markedly reduce anal cancer rates at the population level," they write in the Journal of the National Cancer Institute. "In contrast, very few females with anal cancer were HIV-infected, and more research is needed to understand causes of rising anal cancer incidence in females."
The presence of palpable, clinically involved inguinal lymph nodes (PCIINs) and male gender are both independent risk factors for poor prognosis in anal cancer, confirm the results of a UK analysis.
The researchers analyzed data from 292 patients in the Anal Cancer Trial (ACT) I trial who received chemoradiation between 1987 and 1994. From this, they generated prognostic scores for locoregional failure at 2 years, anal cancer death at 5 years, and overall survival at 5 years.
Regression analysis showed that male gender and PCIINs were independent risk factors for all three endpoints.
In comparison with women, the risk for locoregional failure was 60% greater (36 vs 26%), for anal cancer death was 80% greater (39 vs 25%), and for any death was 56% greater for men (82 vs 57%). Meanwhile, the presence of PCIINs increased the risk for locoregional failure by 87% (40 vs 28%), and for anal cancer death by 83% (45 vs 27%), and led to significantly worse overall survival compared with patients with inpalpable nodes.
After adjusting for gender and lymph node status, the authors also found that lower hemoglobin level increased the risk for anal cancer death, while increased baseline white blood cell count reduced overall survival.
"The use of hemoglobin as a risk-stratification factor may be useful in future trials and may provide a method with which to identify patients who might benefit from future methods of hypoxic modification of radiotherapy," Robert Glynne-Jones (Mount Vernon Center for Cancer Treatment, Northwood, UK) and colleagues write in Cancer.
They add that pretreatment white blood cell count may be prognostic due to the role of inflammation in cancer progression.
