Laryngeal cancer might not be as well known as many of its malignant cousins – but that’s part of the problem. There has been a worrying shortage of epidemiological information about the disease – but, thanks to a team from The Chinese University of Hong Kong (CUHK)’s Faculty of Medicine (CU Medicine), that’s starting to change.

Laryngeal cancer affects both the vocal cords and the larynx, the tube in the throat above the windpipe that houses them. It mainly affects people aged between 45 and 70, and is 13 times more likely to affect men than women. The five year survival rate is about 60%; however, that rises or falls dramatically depending on when the disease is discovered: it can be as high as 90% if it’s diagnosed at an early stage, but as low as 30% later on.

The new study, which has been published in the International Journal of Surgery, looks at where the disease occurs and what causes it, using data from sources including the World Health Organization Global Cancer Observatory, and the Cancer Incidence in Five Continents and Global Disease Burden studies. Previous studies have also looked into the subject, but tend to be based on old data and of limited geographical scope.

The CU Medicine team was led by Dr Jason Huang Junjie, the first author of the study and Research Assistant Professor from The Jockey Club School of Public Health and Primary Care, along with Professor Martin Wong Chi-sang, the senior corresponding author of the study, Professor of The Jockey Club School of Public Health and Primary Care. They teamed up for it with Professor Mellissa Withers, Director of the Association of Pacific Rim Universities (APRU) Global Health Program and a faculty member of the Keck School of Medicine at the University of Southern California.

The results showed that the incidence of laryngeal cancer is related to different places’ per capita GDP, Human Development Index (HDI), and levels of unhealthy lifestyle habits and exposure to metabolic risk factors. The incidence and mortality rates are generally higher in middle- and high-income countries and regions. The Caribbean, and Central, Eastern and Southern Europe are the regions with highest incidence of the disease.

As far as its causes are concerned, the study found, as expected, that smoking is overwhelmingly the main cause, leading to so-called mucosal hyperplasia, which can become cancerous. Next in the list comes alcohol, in particular excessive consumption of spirits. However, a whole range of other factors can also be at play, says Professor Wong.

“Cigarette smoking and alcohol consumption were found to have the strongest relation with laryngeal cancer, and an interaction effect between tobacco and alcohol consumption on the cancer has been identified in previous studies. Nevertheless, other potential risk factors include advanced age, being male, dietary habits – rich in animal products and fats but low in vegetables and fruit – family history of cancer, chemical workplace exposure, gastro-oesophageal reflux and exposure to human papillomavirus.”

Potential risk factors of laryngeal cancer include unhealthy dietary habits – rich in animal products and fats but low in vegetables and fruit.

The study found that, like many serious conditions, including a number of other cancers, laryngeal cancer is at least in part a disease of affluence, occurring at higher rates in richer countries, largely because people in those places are more likely to indulge in the unhealthy habits mentioned above. However, that doesn’t tell the whole story, with the highest incidence occurring both in Europe, where incomes are high but with considerable regional variation, and the Caribbean, which has generally lower levels of wealth, albeit with some high-income pockets.

“In developed countries, smoking, alcohol drinking, unhealthy diet, physical inactivity, obesity, hypertension, diabetes and lipid disorders are relatively more common. On the other hand, the higher number of cases in developed countries may be attributed to an improvement in early cancer detection and interventions targeting risk factors,” says Dr Jason Huang Junjie.

In less wealthy countries, he adds, high rates of the disease could be less to do with lifestyle factors and more to do with levels of healthcare provision. “The higher proportion of population without access to surgery may also have led to the higher mortality rate, as the Caribbean, Eastern and Central Europe have remarkably higher proportions than regions with higher income such as Western Europe and North America.”

Laryngeal cancer affects about 180,000 people a year globally, with close to 100,000 deaths. The incidence is somewhere between 3 and 5%, a number that is decreasing in many places, probably as a result of reduced levels of smoking globally. However, it is worrisome that in some countries, both incidence and mortality rates are increasing among women, showing a reverse trend, a phenomenon that is particularly pronounced in Japan, Switzerland and the Czech Republic. The reasons why are an important subject for further study.

Cigarette smoking and alcohol consumption were found to have the strongest relation with laryngeal cancer.

Professor Wong says, “It is alarming that increases were observed in the female populations and younger subjects from some countries. If no mitigation interventions are implemented, we expect these upward trends to continue. Governments should strengthen cancer prevention efforts, including the active implementation of smoking and alcohol reduction campaigns.”

Armed with the information provided by the study, healthcare professionals will be able to make better decisions about treatment and resource allocation, says Professor Wong.