A saliva test for detecting oropharyngeal cancer caused by human papillomavirus–16 (HPV-16) has scored a world first: It detected such a cancer in an asymptomatic adult.
If the finding can be replicated in a larger cohort of healthy asymptomatic individuals, widespread screening for HPV-16 – the main driver behind skyrocketing rates of oropharyngeal cancer – could be one step closer, the researchers suggested.
“Oropharyngeal squamous cell carcinomas often presents at a late stage with patients suffering huge morbidity as a result of treatment, [so] we must find strategies to detect these cancers earlier,” senior author Chamindie Punyadeera, PhD, Queensland University of Technology in Brisbane, Australia, told Medscape Medical News in an email.
“This study, for the first time, provides a solid scientific foundation to initiate a screening trial in high-risk individuals to detect HPV-driven oropharyngeal cancer, she added. “Saliva testing could be broadly implemented and [used] in a screening trial in the future,” she said.
The case report wasMarch 31 in Frontiers in Oncology.
The saliva test was developed by Dr. Punyadeera and first author Kai Dun Tang, PhD, also from Queensland University of Technology. It is administered as an oral rinse: the individual swishes a saline solution around in his or her mouth for a minute or 2, and then spits the sample into a tube.
The saliva test was being scrutinized in an ongoing HPV-16 DNA prevalence study, which involved 650 healthy participants being tested for oral HPV-16 DNA.
“Of these, 3 have been identified to have persistent oral HPV-16 DNA infection,” the investigators reported.
After having approached these three participants, one middle-aged male who had been consistently HPV-16 DNA positive for a period of 36 months – and whose HPV-16 viral load had been steadily rising over time – was invited to attend an ear, nose, and throat clinic for assessment.
“Initial clinical examination of the oropharynx including palpation and white light revealed no significant abnormalities,” the researchers emphasized.
As Dr. Punyadeera explained, standard clinical assessment for oropharyngeal malignancy includes white light examination for masses, detection of irregularities or asymmetry of the underlying structures and palpation of the tonsil and tongue base.
Cross-sectional imaging with CT or MRI can be helpful as well, she said, but these imaging studies are unable to detect lesions smaller than a few millimeters in size.
In the case of this individual, salivary oral rinse samples had been collected at baseline, and again at 6, 12, and 36 months after study enrollment as well as 2 weeks after the patient decided to undergo a bilateral tonsillectomy.
DNA was extracted from the salivary oral rinse samples, as well as from the tonsillar tissue obtained after resection. HPV-16 DNA genotyping and viral loads were analyzed with a PCR assay.
Results from the salivary samples indicated that the patient’s HPV-16 DNA viral load had increased exponentially across the 36 months of follow-up, from 3.43 copies/50 ng at baseline to 1281.69 copies/50 ng at 36 months.
On surgery, the patient was found to have a 2 mm squamous cell carcinoma in the left tonsil, but all other oropharyngeal tissues were normal and HPV-16 DNA negative.
Two weeks after undergoing the tonsillectomy, the patient’s HPV-16 DNA viral load in the saliva samples became undetectable.
This case report demonstrates that salivary HPV can both detect smaller lesions than either clinical examination or even radiological investigation, and that the same salivary test can likely also be used to monitor treatment response, Dr. Punyadeera commented.