Discussion

There were an estimated 89 400 people in the UK living with HIV at the end of 2016; this is equivalent to a prevalence of 0.16 per cent.⁶ During this year, 42 per cent of newly diagnosed individuals were late presenters and 10 400 people (12 per cent of the total number of HIV patients) were living unaware of their diagnosis.^{Reference Lord, Stockdale, Malek, Rae, Sperle and Raben7,8}

Patients with HIV are at a substantially higher risk of developing cancer than those who are not infected.^{Reference Engsig, Gerstoft, Kronborg, Larsen, Pedersen and Pedersen4} Infection-driven cancers in HIV-positive individuals are already well recognised in the literature, and include: hepatocellular carcinoma caused by hepatitis B and C infections, and lymphoma related to Epstein–Barr virus.^{Reference Zur Hausen9,Reference McLemore, Haigentz, Smith, Nuovo, Alos and Cardesa10} Human papilloma virus (HPV) is known to be an important risk factor for developing head and neck SCC. However, head and neck SCC is also the third commonest head and neck cancer in HIV-infected individuals, behind Kaposi's sarcoma and non-Hodgkin's lymphoma. For this reason, head and neck SCC, although not an acquired immunodeficiency syndrome (AIDS)-defining condition, is an indicator condition for HIV.¹

Testing for HIV infection in patients with indicator conditions is believed to be an effective strategy to help bridge the HIV diagnosis gap that exists in the UK and to help reach the 90-90-90 Joint United Nations Programme on HIV/AIDS target (90 per cent of people living with HIV infection diagnosed, 90 per cent of people diagnosed receiving treatment and 90 per cent of people receiving treatment being virally suppressed).¹¹

Late diagnosis of HIV leads to increased morbidity and mortality, poorer response to antiretroviral therapy, and increased healthcare costs. Late presenters have a 6.6–13-fold increased risk of death, particularly in the first year after diagnosis. The initiation of antiretroviral therapy is now recommended in patients with cluster of differentiation 4 counts of more than 500 cells/μl, because of the decreased risk of malignancy, cardiovascular disease and infection in those who receive early treatment.^{Reference Mocroft, Lundgren, Sabin, Monforte, Brockmeyer and Casabona12,Reference Lundgren, Babiker, Gordin, Emery, Grund and Sharma13}

The purpose of highlighting an indicator condition is to raise awareness that this patient cohort is more likely to have HIV infection, and their contact with the medical profession is an opportunity to test and therefore potentially avoid late presentations.^{Reference Sullivan, Raben, Reekie, Rayment, Mocroft and Esser3}

Human papilloma virus, and traditional risk factors such as smoking and alcohol intake, are still the most important risk factors in this HIV-positive cohort with head and neck SCC. However, it is also known that these lifestyle risk factors are more prevalent in HIV-infected individuals compared to their HIV-negative counterparts.^{Reference D'Souza, Carey, William, Nguyen, Ko and Riddell14}

It has been reported that patients with head and neck cancer and concurrent HIV infection have an excess mortality compared to their HIV-negative counterparts.^{Reference Purgina, Pantanowitz and Seethala15} Exposure to oncogenic factors as listed above certainly contributes to the increased mortality rates, but there is some evidence that this in part could also be because head and neck cancers are more aggressive in HIV-positive patients. Singh et al. showed one and two-year survival rates of 57 per cent and 32 per cent in HIV-positive patients, and 74 per cent and 59 per cent in non-infected patients, respectively.^{Reference Singh, Sabin, Rofim, Shaha, Har-El and Lucente16} These findings were most likely related to the cancer being at a more advanced stage on diagnosis; however, it is unclear as to whether this is related to the presence of HIV.

In the largest case series of HIV-infected head and neck cancer patients to date, D'Souza et al. determined the characteristics and survival of 94 patients.^{Reference D'Souza, Carey, William, Nguyen, Ko and Riddell14} Seventeen per cent of all head and neck SCCs and 55 per cent of oropharyngeal cancers contained HPV16 DNA. There was no significant difference in overall survival between HIV-infected individuals and those who were HIV-negative (63 vs 61 months). It was, however, found that those with cluster of differentiation 4 counts of 200 cells/μl or less at diagnosis had significantly reduced survival than those with counts of over 200 cells/μl (16.1 vs 72.8 months, p < 0.001).^{Reference D'Souza, Carey, William, Nguyen, Ko and Riddell14} Thus, despite risk factors being similar, the relative importance of HPV-driven cancers and their outcome in late-stage HIV infection does determine patient outcome.

This observational study indicates that HIV testing amongst newly diagnosed head and neck SCC patients is widely underperformed and poorly understood. Historically, there has often been a stigma around discussing HIV risk factors and addressing HIV testing with patients. However, it seems that the main barrier to HIV testing has been the lack of awareness of head and neck SCC being an indicator condition for HIV.

It is important that healthcare professionals who do not work in the field of HIV are aware of the importance of HIV testing for indicator conditions and have the confidence to consent patients for testing on a routine basis. The HIV testing has to be built into the patient's diagnostic investigation, to ensure there are no missed cases. This is true of other conditions within the scope of the head and neck MDT, such as lymphoma, which often presents to ENT clinics early in the patient journey. Once a patient is diagnosed with HIV infection, there need to be clear and timely referral pathways in place, to ensure that both the HIV and head and neck cancer are treated expediently. Increased testing provides us with the opportunity to decrease the number of people living with HIV who are not aware of their status, and allows us to improve the outcome of individual patients under our care with head and neck SCC.