Thursday, March 23, 2023

I don’t suppose too many of us are familiar with the areca palm, but it grows widely in India and throughout much of the rest of Asia and east Africa. Its seed, the areca nut, is also known as the betel nut. It is chewed by hundreds of millions of people throughout India, southern China and other countries, mostly by men.

Betel nut chewing causes a mild euphoric and stimulatory effect, along with heightened alertness. The main psychoactive chemical constituent in the betel nut is arecoline; it appears to be similar chemically to nicotine.

Betel nut chewing has been associated with a variety of harmful health effects, but the one that interests us, of course, is its carcinogenic impact. In 2003, the International Agency for Research on Cancer classified betel nut chewing as a class 1 (definite) carcinogen. It is associated with the development of squamous cell carcinomas of the oral cavity and esophagus. Tobacco and alcohol use are also common in India and thus their joint use with betel nut chewing has led to extremely high rates of oral cavity cancer. It ranks as the third most common cancer in India as well as other countries where this habit is prevalent. Exactly what constituent of betel nuts is carcinogenic currently remains unknown. The chewing does cause chronic irritation in the oral cavity lining, and this irritation may be partly responsible. It is also apparent that betel nut chewing also causes the development of oral leukoplakia, a precursor lesion for oral cancer.

Multiple observational studies have been done to explore the association of betel nut use with oral cavity cancer. One example is a cohort study in India that found an incidence rate of oral cancer of 31/100,000 among 7,000 betel nut users versus zero oral cancers among a similar-sized group of non-users. The comparable incidence rate in the U.S. would be about 10 per 100,000/year for males.

Because of the high rate of oral cancer in India, there has been considerable interest in screening for oral cancer. A randomized controlled trial was conducted in the province of Kerala in India between 1991 and 1992 where the incidence rate of oral cancer was 16/100,000, mostly attributable to betel nut chewing. In this trial, different neighborhoods or health districts were randomized, rather than individuals. Thus, seven districts were assigned to receive the screening intervention while six districts were randomized to serve as controls. In the intervention districts, community health workers were trained to conduct a visual inspection and palpation of the oral cavity and tongue during home visits. Those with suspicious lesions were referred to specialty clinics. This screening was repeated every three years for three rounds. No screening was provided in the control districts. In the first year, there were 59,894 residents in the screened districts and 54,707 residents in the control districts. Each year more individuals were screened annually in the intervention districts, until ultimately 191,873 individuals participated in the study. After nine years, the incidence of oral cancer did not differ significantly between the screened group and the control group (43.7/100,000 versus 37.6/100,000). The stage distribution of the detected cancers was lower in the screened districts than in the control districts, but there was no significant difference in the mortality rate (16.7/100,000 versus 20.7/100,000, not statistically significant).

I myself can recall seeing the hygienist in my dental practitioner’s office and undergoing an oral exam for tumors. Since I don’t smoke, don’t drink alcohol to excess, nor chew betel nuts, I really have to wonder if this was a good use of her time. A study of 24 dentists in London who screened 2,027 high-risk subjects (heavy smokers and drinkers) did establish that the dentists had a very high sensitivity and specificity with regard to the identification of suspicious lesions. Thus, dental professionals are good at screening for malignancy.

Nevertheless, recommendations for cancer screening generally require that there be the demonstration that cancer mortality will be reduced by screening. Even the large study in Kerala, India, I described could not demonstrate that. As a result, the U.S. Preventive Services Task Force does not recommend oral cancer screening in the U.S., even for those at high risk.

Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.

This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.

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