HIV update - 31st January 2018

Cancers in people with HIV

Thanks to the development of safe and effective HIV treatment, most people with HIV can now expect to live well into older age. But this means that the diseases of ageing – including some cancers – are now an important cause of serious illness among people with HIV. This issue of HIV update focuses on cancer and the large number of cancers which are linked to smoking.

But which cancers do people with HIV develop? Are people with HIV at greater risk of cancer than other people?

A very large American study has just published an analysis of people over the age of 50. Among just over 183,000 people living with HIV who were followed for an average of five years each, there were just over 10,000 cancers. This compares to just under 9000 cancers that would be expected if studying the same number of people of the same age in the general population.

The most common cancers in this group of people over the age of 50 living with HIV were:

• Lung cancer (1725 cases)
• Prostate cancer (1341 cases)
• Non-Hodgkin lymphoma (1222 cases)
• Liver cancer (805 cases)
• Anal cancer (524 cases)
• Oral or throat cancer (461 cases)
• Kaposi's sarcoma (338 cases)
• Bowel cancer (360 cases)
• Breast cancer (329 cases)
• Hodgkin lymphoma (253 cases)
• Other cancers (3013 cases)

For some cancers, rates in people with HIV were actually lower than those in the general population. This was the case for prostate cancer, breast cancer and bowel cancer. So although prostate cancer was the second most common cancer in this predominantly male cohort of people with HIV, rates were actually half of those found in the general population.

However, there are several cancers where rates were higher in people with HIV than people in the general population – Kaposi's sarcoma, anal cancer, Hodgkin lymphoma, non-Hodgkin lymphoma, cervical cancer, liver cancer, lung cancer and oral/throat cancer.

In general, the risk of having a cancer progressively increases as you get older. This is also true for people with HIV – people were more likely to develop lung, prostate and bowel cancer in their sixties or seventies than in their fifties.

But the gap between HIV-positive people and HIV-negative people did not increase as people got older – in fact it tended to narrow. This suggests that “premature ageing” due to HIV is not an accurate explanation for cancer in people with HIV.

The researchers summed up the biological processes which appear to interact and affect the risk of cancer in people with HIV:

• Factors related to ‘normal’ ageing, including a gradual deterioration of the immune system.
• Factors associated with HIV infection, its impact on the immune system and HIV treatment.
• Other characteristics of people living with HIV that affect cancer risk, such as smoking and viral infections.

To reduce the risk of cancer, key steps are taking HIV treatment to restore immune function, treating co-infections like hepatitis C, making lifestyle changes such as stopping smoking, and attending screening.

For more information, read NAM’s factsheets: 'Cancer and HIV', 'Non-Hodgkin lymphoma and HIV', 'Anal cancer and HIV', 'Kaposi's sarcoma and HIV', 'Lung cancer' and 'HIV and the ageing process'.

Smoking and cancer

In the last study, lung cancer was the most common cancer in people with HIV. Also, rates of lung cancer were higher in people with HIV than in the general population. This is mostly because rates of smoking are very high amongst people with HIV, compared to the general population. It also appears that a weakened immune system may make lung cancer more likely to develop in HIV-positive smokers than in HIV-negative smokers.

Smoking is the main risk factor for lung cancer, and contributes to several other types of cancer – including cancers of the mouth, throat, bladder, kidney, pancreas, bowel, anus, stomach and cervix. 

Another large American study, drawing on slightly different data sources, has tried to estimate the proportion of cancers in people with HIV in which smoking is the principal cause. They believe it is one in five.

In particular, smoking was thought to cause 94% of cases of lung cancer. It also caused 32% of cases of anal cancer – in other words, if nobody living with HIV smoked, there would be a third fewer cases of anal cancer.

Finally, a study has looked at outcomes in people who had liver cancer, comparing people who smoked after their cancer diagnosis and people who did not. Liver cancer can be a complication of hepatitis B or C, especially if the viral infection had been left untreated for some time. It’s worth noting that this is a study of people with hepatitis B or C – it did not include people who also had HIV.

The researchers found that liver cancer developed at a younger age in smokers, and that smokers were three times more likely to die after their diagnosis. This could be because smokers were generally less healthy or less likely to stick with their treatment. But smoking is also known to worsen liver fibrosis and might also directly influence the progression of liver cancer. 

For more information, read NAM’s factsheet 'Smoking' and 'Managing advanced liver disease' in the booklet 'HIV & hepatitis'.

Older HIV drugs and liver damage

A history of treatment with some older anti-HIV drugs can have a lasting negative impact on liver health, according to a small German study. But having an undetectable viral load protects the liver, outweighing the harm that had been done by older drugs.

Some anti-HIV drugs which were commonly used in the 1990s and early 2000s are known to sometimes harm the liver. These drugs are now rarely used, but many people took them before alternatives became available. They include zidovudine (also known as AZT and a component of the Combivir pill), stavudine (also known as d4T) and didanosine (also known as ddI).

The researchers looked at data on 333 people living with HIV that were collected from 2009 to 2011. Most were men and they had been diagnosed with HIV for an average of ten years. One third also had hepatitis C.

In terms of the older anti-HIV drugs, a third had previously taken zidovudine, a quarter stavudine and 12% didanosine.

The researchers were particularly interested in the 18% of people who had significant fibrosis (scarring of the liver, i.e. the development of hard, fibrous tissue) and the 8% who had cirrhosis (more advanced scarring).

Having hepatitis C was by far the most important risk factor for fibrosis or cirrhosis, raising the risk fivefold. And among people with hepatitis C, people who had previously had zidovudine treatment had a fourfold increased risk.

In those who did not have hepatitis C, having previously had didanosine treatment raised the risk of fibrosis or cirrhosis threefold.

But having an undetectable viral load halved the risk. The researchers commented that viral suppression outweighs the damage done by previous anti-HIV drugs.

For more information, read 'The liver' in NAM’s booklet 'HIV & hepatitis'.