The risk of cancer
is increased twofold for people with HIV compared to individuals in the
general population, Danish investigators report in the online edition of AIDS. But the increased risk was almost
entirely due to higher incidence of smoking-related cancers and also malignancies
caused by viral infections. The risk of other cancers did not differ between
the people with HIV and people who did not have HIV.
“In the present
study we found that the increased risk of non-AIDS cancer was largely confined
to cancers associated with smoking and viral infections,” write the authors.
“The risk of cancers that are not considered strongly related to smoking or
viral infections did not differ between the HIV-infected and the background
population, and the impact of immune deficiency was limited.”
cancers are an increasingly important cause of serious illness and death among people with HIV. The exact causes are uncertain. However, possible
explanations include high rates of smoking, a high burden of viral co-infections
such as hepatitis C virus (HCV) and human papillomavirus and immune suppression
caused by HIV.
Denmark wanted to establish the proportions of cancers in people living with HIV attributable
to smoking, viral infections, and HIV-related immune suppression.
compared the incidence of cancer between people with HIV and matched controls
in the general population. Results were stratified according to smoking status
and immune deficiency. Cancers were categorised as smoking-related, virus-related
population consisted of 3503 individuals who received care between 1995 and
2011. Their average CD4 count at baseline was 450 cells/mm3. At the
time of inclusion in the study, 77% were taking HIV therapy and, for 92% of
follow-up time, the people with HIV were taking antiretroviral therapy.
population consisted of 12,979 individuals.
There were 157
cancer diagnoses among the people living with HIV compared to 255 diagnoses among
incidence of cancer was twice as high in people with HIV compared to the
controls (IRR = 2.0; 95% CI, 1.6-2.5).
The incidence of
cancers related to viral infections was almost twelvefold higher in the
HIV-positive population than in the HIV-negative controls (IRR = 11.5; 95% CI,
6.5-20.5). Incidence of smoking-related cancers was almost threefold higher
among people with HIV (IRR = 2.8; 95% CI, 1.6-4.9). The risk of other cancers
did not differ between the people living with HIV and the HIV-negative controls.
smoking-related cancers associated with current smoking was significantly
higher among the people living with HIV (IRR = 21.35; 95% CI, 2.88-158.5) than
the controls (IRR = 4.12; 95% CI, 1.74-9.78).
For the people
with HIV, a lowest-ever (nadir) CD4 count below 200 cells/mm3 was associated
with a more than threefold increase in the risk of lung cancer (IRR = 3.54;
95% CI, 1.00-12.59). No patients with a nadir CD4 count above 200 cells/mm3
developed a smoking-related cancer.
and virus-associated malignancies accounted for 23% and 43% of cancers
diagnosed in the HIV-positive population. Virological cancers were rare in the
The fractions of
all cancers in the HIV-positive population attributable to smoking and viral
infections were 27% and 49%, respectively.
For cancer types
considered associated with smoking, the proportion attributed to smoking was
91%. The proportion of virus-related cancers attributed to having
HIV was also 91%.
For cancers not
strongly related to smoking or viral infections, the proportion attributable to
being HIV positive and immune deficiency were 0%.
“We found that HIV
patients, with long term-engagement in care, had an increased risk of cancers
that are considered strongly related to smoking and viral infections,” comment
the authors. “They did not have increased risk of other cancers compared with
the background population. We found no association between immune deficiency
and non-virological cancers that are not strongly related to smoking.”