Detection and Prevention of Oral Cancer: Are Screening Methods Effective?

In dentistry, screening for oral cancer by visual inspection and palpation is an essential part of a clinician’s routine practise. Yet achieving the goals of screening—identification of precancerous lesions or cancers so that interventions can reduce malignant transformations or improve chances of survival—can be a major challenge. Diagnostic delays mean that more than half of all people with oral and pharyngeal cancer have regional or distant metastases at the time of diagnosis¹.

Three recent reviews examined the latest evidence on the effectiveness of screening programs for oral cancer and arrived at generally similar conclusions: there isn’t enough evidence to definitively say whether oral cancer screening is effective or not. The take-home advice for dentists? Despite inconclusive evidence, dentists should remain vigilant for signs of precancerous or cancerous lesions in all patients while performing routine follow-up and new patient oral examinations.

“Dentists should use the opportunity of a routine oral examination to screen for oral cancer,” says Dr. Catherine Poh, associate professor in the UBC faculty of dentistry and researcher in the areas of community screening and management of high risk oral precancerous lesions. “Soft tissue screening is our responsibility as dentists—it has the potential to detect a variety of irregularities, including early signs of mouth or throat cancer. Three minutes could save a life!”

Cochrane Collaboration

A Cochrane Collaboration review² assessed current screening methods— visual examination and adjunctive technologies like toluidine blue, fluorescence visualization or brush biopsy—and found no evidence of their effectiveness in reducing mortality from oral cancer. The study authors found some evidence that a visual examination reduces the death rate for oral cancer in high-risk individuals—those who used tobacco or alcohol or both—although the evidence came from only one study.

Another Cochrane Collaboration review³ attempted to evaluate the diagnostic accuracy of an oral cancer screening examination and other adjunctive technologies, but the substantial variability in the included studies made it difficult to compare studies or conduct a pooled analysis of the data. The review authors conclude that general practitioners should “remain vigilant for signs of PMD (potentially malignant disorders) and oral cancer while performing routine oral examinations in practice.”

U.S. Preventive Services Task Force

A review by the U.S. Preventive Services Task Force (USPSTF)⁴ found there was inadequate evidence that the oral screening examination—visual examination and palpation—performed by primary care providers accurately detects oral cancer or results in improved morbidity or mortality through treatment. However, the USPSTF statement clearly notes that its recommendation on oral cancer screening does not pertain to dentists or otolaryngologists. Despite the lack of evidence supporting a beneficial outcome to screening, the USPSTF authors recognize that clinical decisions “... involve more considerations than evidence alone,” and must take into account the specific patient or situation.

Although tobacco and alcohol use are considered the major risk factors for oral cancer, risk also increases with age. An increasingly important risk factor for oropharyngeal cancer is sexually transmitted oral HPV infection (HPV-16). Yet all adults—not only high risk individuals—should be screened for oral cancer, according to Dr. Poh, who says there has been an increase in the number of younger-age oral cancer patients and patients without obvious known risk factors. Adds Dr. Poh, “It’s time to consider and conduct a large-scale, multi-centre study with a standardized protocol to investigate this potentially life-saving measure. What’s needed is more solid research-based evidence to answer the questions ‘Should we screen or not screen for oral cancer? Are adjunctive techniques useful, and what is their value in screening?’”

In Canada, approximately 4100 new cases of oral cancer and 1150 deaths from oral cancer were estimated for 2013⁵. Globally, oral cancer is the sixth most common cancer and its rates are increasing.

Dr. Poh was a co-author of a JCDA article⁶ that includes step-by-step advice on performing a head and neck evaluation to screen for oral cancer. See: www.cda-adc.ca/jcda/vol-72/issue-5/413.pdf.