Chewing coca leaves increased the risk of developing oral squamous cell cancer

Argentine scientists conducted a case-control study and found that chewing coca leaves may increase the risk of developing oral squamous cell cancer. As reported in the journal Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, the study involved 62 patients and 180 controls.

Approximately 90 per cent of oral malignancies are classified as oral squamous cell cancer. That said, this type of tumour is a multifactorial disease. Classic risk factors associated with it include tobacco and alcohol use and betel nut consumption. However, there are also non-canonical risk factors - for example, low fruit and vegetable intake, chronic inflammation and oral dysbiosis.

In addition, the researchers identified various geographical differences in the epidemiological and clinical profile of oral squamous cell cancer in Latin America. Notably, one province in northern Argentina with a high consumption of coca leaves (Erythroxylum coca) was found to have a specific association with a high incidence of oral squamous cell cancer. Putting coca leaves in the back of the mouth, being an ancient practice, is considered to have health benefits, but there are few epidemiological studies linking coca leaf chewing and oral squamous cell cancer.

Therefore, a team of scientists led by Gerardo Gilligan of the National Autonomous University of Mexico studied the association between coca leaf chewing and the development of oral squamous cell cancer among patients seeking medical care at the Hospital Señor del Milagro in Salta, Argentina. A total of 242 patients (mean age 58 years) were included in the study: including 62 patients and 180 controls. Patients with oral squamous cell cancer were more likely to smoke (p=0.001), chew coca (p<0.001) and have poor oral health with visible biofilm and severe periodontal disease or extensive caries (p=0.02) compared to controls.

In multivariate analysis, smoking (odds ratio 2.77, p=0.0139), coca chewing, (odds ratio 2.98, p=0.0007) and poor oral health (odds ratio 3.1, p=0.0006) remained independently associated with the development of squamous cell cancer. When risk factors were analysed stratified, it was found that the group of people who did not chew coca showed no association with the above three risk factors. Conversely, in the coca chewing group, smoking and poor oral health were directly associated with cancer development.

So far, these results do not clearly link coca leaf consumption to the development of oral squamous cell cancer due to the small amount of observations and the influence of confounding factors. However, this study may initiate further work on the effects of coca leaves on the development of oral tumours.