Dental caries show ‘unexpected’ relationship with head and neck cancer

By Joanna Lyford, Senior medwireNews Reporter

People with dental caries have a reduced risk for developing head and neck squamous cell carcinoma (HNSCC), a large case-control study has found.

The finding is “unexpected” since dental caries are considered a sign of poor oral health, say the researchers, who call for future studies to assess the possible benefits of cariogenic bacteria and associated immune responses.

A team led by Mine Tezal (State University of New York at Buffalo, USA) evaluated the relationship between dental caries and incident primary HNSCC in 620 patients treated at the Roswell Park Cancer Institute.

In all, 399 of the participants were newly diagnosed with HNSCC (cases), of whom 146 (36.6%) had oral cavity SCC, 151 (37.8%) had oropharyngeal SCC, and 102 (25.6%) had laryngeal SCC.

The remaining 221 patients were free of cancer or dysplasia (controls); compared with controls, cases were older and more likely to be male, smokers, users of alcohol, and married.

Comparison of oral characteristics found that patients with HNSCC had fewer teeth with caries (1.58 vs 2.04), fewer endodontic treatments (0.56 vs 1.01), fewer crowns (1.27 vs 2.10), and fewer fillings (5.39 vs 6.17) than did patients without cancer; all differences were statistically significant.

However, two other oral variables showed the reverse pattern, with cancer patients having more severe alveolar bone loss (4.03 vs 2.44 mm) and more missing teeth (13.71 vs 8.50) than controls.

A composite variable of “decayed, missing, and filled teeth” was similar between the groups.

After adjusting for multiple confounders, people in the upper tertiles of caries, crowns, and endodontic treatments were significantly less likely to have HNSCC than those in the lower tertiles, with odds ratios (OR) of 0.32, 0.46, and 0.55, respectively.

Further analysis found that dental caries were associated with HNSCC in patients with oral cavity SCC and oropharyngeal SCC but not in those with laryngeal SCC, with ORs of 0.30, 0.27, and 0.89, respectively. The association was also significant among never-smokers and never-drinkers.

Writing in JAMA Otolaryngology–Head & Neck Surgery, Tezal and colleagues say that their finding of an inverse association between dental caries and HNSCC, while unexpected, has “validity” and “is not likely a chance finding.”

They note that research evaluating the role of oral factors in the natural history of HNSCC is lacking and hypothesize that cariogenic bacteria may protect the host against chronic inflammatory disease and HNSCC.

“We could think of dental caries as a form of collateral damage and develop strategies to reduce its risk while preserving the beneficial effects of the lactic acid bacteria,” write Tezal et al.

They continue: “Future studies assessing the potential effects of the oral microbiome and associated immune responses on HNSCC will help elucidate the biological mechanism of the clinical association that we have observed in this study.”

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