Dental Trauma May Play a Role in Oral Cancers

Roxanne Nelson

November 07, 2014

Chronic dental irritation might play a role in the development of oral cancers, especially in nonsmokers, according to a study published online November 6 in JAMA Otolaryngology–Head & Neck Surgery.

The authors note that oral cavity cancers occur predominantly at sites of potential dental and denture trauma; this is particularly true for nonsmokers who lack other established risk factors.

But more significant was the difference in the location of the cancers they observed in their retrospective analysis of 724 patients. "The key finding of this study is that the location where oral cavity cancers arise is different in smokers and nonsmokers," write lead author Brendan J. Perry, BSc, MBBS, from the Princess Alexandra Hospital in Brisbane, Australia, and colleagues.

The majority of oral cavity cancers in patients who were nonsmokers occurred in areas where teeth or dentures can rub and cause irritation.

For smokers, most of the tumors were on the edge of the tongue (107 of 303 cases), on the floor of the mouth (82 cases), and on the retromolar trigone (38 cases).

But tumors on the edge of the tongue, a lesion site that can potentially be associated with chronic dental trauma, were much more common in nonsmokers than in current or former smokers (66% vs 35%; P < .001).

In addition, in current or former smokers, the incidence of cancer on the edge of the tongue was 20% higher than the incidence of cancer on the floor of the mouth. In comparison, nonsmokers had a nearly 6-fold higher incidence of cancer on the edge of the tongue than on the floor of the mouth (57 vs 10 patients).

Factors Unclear

A relatively high incidence of oral squamous cell carcinoma (SCC) in nonsmokers has been reported, especially in women who are nonsmokers and/or lack other established risk factors, note the authors. Cigarette smoking and alcohol are the most recognized causative factors in the development of oral cavity malignancies.

Human papillomavirus (HPV) has also been established as a known and potent carcinogen within the oropharynx, but the authors note that the role of the virus in mouth cancer is not as clear.

Although there have been a few studies suggesting that chronic irritation from dental trauma or poor fitting dentures play a role in the development of oral cancer, it is not widely accepted as a carcinogen, the authors point out.

High Rates in Female Nonsmokers

To assess the role of chronic dental trauma in the development of oral cancer, Dr Perry and his team analyzed 881 cases of oral and oropharyngeal tumors that occurred during a 10-year period (2001 to 2011) at an Australian hospital.

Of the 724 patients eligible for inclusion, 334 had oropharyngeal cancer and 390 had mouth cancer. Smoking status was similar in the two groups. Of patients with oropharyngeal cancer, 48 were lifelong nonsmokers, 266 were current smokers, and 20 were former smokers. For mouth cancer patients, 87 were lifelong nonsmokers, 276 were current smokers, and 27 were former smokers.

The average age at diagnosis was 60 years for patients with oropharyngeal cancer and 61.7 years for those with mouth cancer. The proportion of men in the oropharyngeal and mouth cancer groups was 79% and 65%, respectively.

During the 10-year study period, the incidence of mouth cancer in women was almost twice that of oropharyngeal cancer (135 vs 69 cases). In men, the incidence of mouth and oropharyngeal cancer was similar (255 vs 265 cases).

For nonsmokers, oral cavity lesions were more common in women than men (61% vs 39%). In contrast, for smokers, oral cavity lesions were less common in women (72% vs 28%).

In nonsmoking men, the number of cases of oropharyngeal and mouth cancer were similar (36 vs 34 cases). However, in female nonsmokers, there were 4 times as many cases of mouth as oropharyngeal cancer (53 vs 12 cases).

Data on alcohol use were difficult to interpret, say the authors, because many patients reported being social drinkers. However, none of the nonsmokers reported heavy drinking.

Dr Perry and his colleagues note that epithelial warts that are caused by HPV are known to implant at sites of trauma. Thus, HPV could be a potential cocarcinogen with dental trauma.

"Given that chronic irritation is a key factor in the development of tumors elsewhere in the body, this study provides further evidence that dental trauma could be a significant cause of oral cavity SCC, possibly the major cause in lifelong nonsmokers," conclude the authors. "This study supports other studies showing that women are particularly prone to mouth cancer, even when they do not smoke, and that cancers occur more often on the lateral tongue in young people and where dentures rub in elderly people."

The authors have disclosed no relevant financial relationships.

JAMA Otolaryngol Head Neck Surg. Published online November 6, 2014. Abstract

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