Hepatitis C doubles the risk of head and neck cancers

Hepatitis C infection doubles the risk of developing cancers of the oral cavity, upper throat and larynx, a meta-analysis of eight studies has shown and the study authors say that people with hepatitis C should be checked regularly for these cancers.

The findings are published in the journal Oral Oncology.

Hepatitis C is linked to the development of several types of cancer apart from hepatocellular carcinoma (liver cancer), including non-Hodgkin lymphoma. Some studies have shown that people with hepatitis C are at higher risk of developing several types of head and neck cancers, but these studies have been small and estimates of the increased risk vary.

Head and neck cancers are defined as those occurring in the oral cavity, the nose and sinuses, the salivary glands, the back of the nose and throat (nasopharynx), the upper throat (oropharynx), the lower throat (hypopharynx) or the voice-box (larynx). These cancers are most often caused by smoking and alcohol. Oropharyngeal cancer is often caused by human papillomavirus.

Almost all head and neck cancers start in the squamous cells that line the mouth, throat and nose. Cancers of the mouth are the most common head and neck cancers. Approximately 12,000 head and neck cancer were diagnosed in the United Kingdom between 2015 and 2017 and head and neck cancers cause 450,000 deaths worldwide each year.

The risk of developing a head or neck cancer is relatively low, although the incidence of these cancers is on the rise. Men are about twice as likely as women to develop one of these cancers. The lifetime chance of developing oral cancer is around one in fifty for men born after 1960 in the United Kingdom, Cancer Research UK has calculated. The risk of other head and neck cancers is lower. Head and neck cancers are more common in Asia.

Investigators from the United Kingdom, Italy and United States carried out a meta-analysis of published studies of head and neck cancer risk in people with hepatitis C.

They identified eight studies (3 case control and 5 observational studies) that reported on the risk of head and neck cancers in people with confirmed hepatitis C infection.

The case control studies matched 1625 cases of head and neck cancers with 2561 controls. Observational cohort studies (three in people with viral hepatitis) reported 58 cases.

Seven studies reported on the association between hepatitis C and oral cancers, finding that people with hepatitis C were approximately twice as likely as others to develop oral cancer (pooled relative risk 2.13, 95% CI 1.61-2.83).

Five studies reported on the risk of oropharyngeal cancer, finding that people with hepatitis C were approximately twice as likely as others to develop oropharyngeal cancer (RR 1.81, 1.21-272).

Three studies reported on the risk of laryngeal cancer, showing that people with hepatitis C were approximately two-and-a-half times more likely than others to develop laryngeal cancer (RR 2.51, 1.11-5.94).

Only two studies reported on the risk of hypopharyngeal cancers and this did not show an increased risk in people with hepatitis C.

The association between hepatitis C and head and neck cancers persisted after people with HIV co-infection were excluded from the analysis (immunosuppression caused by HIV raises the risk of some cancers).

The authors say that the mechanism through which hepatitis C might influence cancer development is unknown, although the virus can be isolated from saliva and has been found in cancer epithelial cells in people with oral cancer. But the authors also acknowledge that studies included in this analysis did not carry out sub-group analyses which took into account smoking, alcohol consumption or human papillomavirus infection, each of which might be more prevalent in people with hepatitis C.

Doctors treating people with head and neck cancers should consider the possibility of undiagnosed hepatitis C and liver specialists should carry out regular checks for head and neck cancers in their patients with hepatitis C, the authors conclude.