Download Dental caries show `unexpected` relationship with head and neck cancer

Dental caries show ‘unexpected’ relationship with head and neck cancer
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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Tooth Cavities Linked to Lower Risk of Head, Neck Cancer in Study
Bacteria involved in cavity formation may have some cancer-protective effect, researcher says, but
skeptics aren't sure
Tooth Cavities Linked to Lower Risk of Head, Neck Cancer in Study
THURSDAY, Sept. 12, 2013 (HealthDay News) -- People with more cavities in their teeth may have a
reduced risk for some head and neck cancers, a new study suggests.
That's because lactic acid bacteria produced by cavities may be protective against cancer cells, the study
authors said.
"This was an unexpected finding since dental cavities have been considered a sign of poor oral health
along with periodontal disease, and we had previously observed an increased risk of head and neck
cancers among subjects with periodontal disease," said lead researcher Dr. Mine Tezal, an assistant
professor at the University at Buffalo, State University of New York.
Tezal was quick to note, however, that the finding doesn't mean people should let cavities develop in
hopes of preventing these cancers.
"The main message is to avoid things that would shift the balance in normal microbial ecology, including
overuse of antimicrobial products and smoking. Rather, you should maintain a healthy diet and good
oral hygiene, by brushing and flossing," she said.
The report was published Sept. 12 in the online edition of JAMA Otolaryngology -- Head & Neck Surgery.
For the study, Tezal's team evaluated 399 patients with head and neck cancers, comparing them to 221
similar people without cancer.
The investigators found that the people with the most cavities were the ones least likely to have head
and neck cancer, compared to those with the fewest cavities. Those with the most cavities had a 32
percent lower risk even after factors such as sex, marital status, smoking and alcohol use were taken
into account.
"It is important to point out that missing teeth and decayed filled teeth, a widely used measure of tooth
decay, were not associated with head and neck cancers," Tezal said.
Cavities are caused by lactic acid produced by bacteria such as streptococci, lactobacilli, actinomycetes
and bifidobacteria, the same kinds of bacteria used in yogurt production, Tezal said.
"These bacteria have important roles in digestion, as well as in local mucosal and systemic immunity,
and their reduction has been associated with chronic inflammatory diseases, allergies, obesity and
cancer," she said.
Tezal said these bacteria could be a key to preventing some head and neck cancers.
"We could think of dental cavities as a collateral damage, and develop strategies to reduce their risk
while preserving the beneficial effects of the lactic acid bacteria," she said.
However, Dr. Joel Epstein, a diplomat of the American Board of Oral Medicine who was not involved
with the study, said its "limitations are many." Among these were the small study size and focus on
current cavities only.
"Tooth loss early in life is typically related to cavities and trauma, and late due to periodontal disease,
and this was not assessed in the study," said Epstein, a consultant with the division of otolaryngology
and head and neck surgery at the City of Hope, in Duarte, Calif.
"The authors and correlation do not prove cause and effect," he said. "Also, even if caries is associated
with reduced cancer risk -- seems very unlikely -- the dental damage, and infection risk of dental disease
carries its own risk."
More in-depth studies that "must be done are not done -- this is a real problem of statistical
correlation," Epstein said.
Another expert agreed that the findings are preliminary, but said that if confirmed, they might lead to
new ways to prevent or treat head and neck cancers.
"We see a mechanism that may protect against mouth cancer, and may be a potential strategy either as
part of prevention or treatment of oral cavity cancer," said Dr. Dennis Kraus, director of the Center for
Head & Neck Oncology at the New York Head & Neck Institute at Lenox Hill Hospital, in New York City.
"This is a fascinating first step," Kraus said.