EMERGING TESTS

HPV DNA from Oral Rinse Samples May Be Prognostic Marker for Head, Neck Cancer

Samples collected from a mouth rinse can detect human papillomavirus (HPV) DNA. These easily collected samples might provide important monitoring information for patients with certain head and neck cancers.

Two recently published studies shed light on both the feasibility of using oral gargle samples and the potential clinical utility of HPV viral load surveillance during and following primary treatment. Both studies show the viability of using oral gargle rinse samples. However, one study was able to show that detection of persistent HPV DNA in oral rinses following primary treatment was tied to poorer patient outcomes.

Most of the clinically relevant HPV genotypes found in oropharyngeal squamous cell carcinoma tumors can be detected using oral gargle samples, according to a study published March 28 in JAMA Otolaryngology Head Neck Surgery.

“Currently the preferred method of HPV status determination is p16 immunohistochemistry, which does not provide specific HPV genotype information,” write the authors, led by Laura Martin-Gomez, M.D., Ph.D., from Moffitt Cancer Center, Tampa, Fla. “As development of HPV-targeted treatment approaches, such as genotype-specific therapeutic vaccines, moves forward, it may be important to adapt an HPV detection method that can determine the specific HPV genotypes for each patient.”

Adult, male patients with newly diagnosed squamous cell carcinoma of the oropharynx (stage I to IV; May 2014 through October 2017) were evaluated. Paired oral gargle and tumor specimen samples were available for 171 men. A highly sensitive in vitro reverse hybridization assay (DDL Diagnostic Laboratory) was used to detect HPV DNA in both sample types.

The researchers found that the detection rate of HPV genotypes was 93.0 percent in tumor specimens and 82.8 percent in oral gargle samples. Only one oral gargle sample failed DNA quality assessment. Of the 171 paired gargle and tumor specimens, there was 74 percent agreement for HPV 16 and 94 percent agreement or higher for all other HPV types, including the high-risk HPV 18 genotype. The oral gargle samples detected low-risk HPV genotypes that were not identified in tumors, but these low-risk genotypes were always a coinfection with high-risk genotypes. Multiple HPV types were present in 7.6 percent of the tumor specimens and 9.9 percent of the oral gargle samples.

“Oral gargle samples are reliable, noninvasive sources of HPV DNA in patients with known oropharyngeal squamous cell carcinomas,” wrote Ricardo Ramirez and Jose Zevallo, both from Washington University in St. Louis, Mo., in an accompanying editorial. “Unfortunately, their study does not bring us any closer to defining practical, clinically relevant applications for this technology.”

However, a second, independent study published May 2 in JAMA Oncology provides some evidence that HPV DNA samples derived from oral rinses hold promise as a marker for treatment response and risk of progression among patients with oral and oropharyngeal cancers. The study showed that the prevalence and viral load of tumor-type HPV DNA decreased rapidly with therapy, but that persistent HPV DNA detection was associated with increased risk of cancer recurrence and death.

“Our data suggest that persistent tumor-type oral HPV DNA identified a subset of HPV-positive patients with increased risk of recurrence and consequently inferior overall survival,” write the authors led by Carole Fakhry, M.D., from Johns Hopkins University in Baltimore, Md. “Patients with persistent HPV DNA may benefit from close clinical surveillance or adjuvant therapy.”

In the present study tumor samples were assessed for 37 HPV DNA types, while HPV load was measured in oral samples for 22 HPV types using type-specific real-time polymerase chain reaction. Samples were considered positive if HPV copy number was above the lower-limit of reproducibility (≥3). In total, 396 patients (217 had oropharyngeal cancer; 170, oral cavity cancer) with newly diagnosed oral cavity or oropharyngeal squamous cell carcinomas were evaluated at two locations from July 11, 2011, to May 7, 2016. Oral rinse samples (a 30-second rinse and gargle with saline) were prospectively collected at diagnosis and at completion of primary therapy, as well as weekly during radiotherapy.

The researchers found that just over half of patients overall (51 percent) had HPV-positive tumors, although a higher percentage of oropharyngeal cancer patients were HPV-positive (86.2 percent). For detection of any oral HPV DNA at diagnosis, oral rinse samples had a sensitivity of 84 percent, specificity of 88 percent, a positive predictive value of 88 percent, and a negative predictive value of 84 percent for a diagnosis of an HPV-positive tumor. Among the 202 patients with HPV-positive tumors, nearly 80 percent had the same HPV DNA type detected in the oral rinse sample and in the tumor at baseline.

The prevalence and load of tumor-type HPV decreased significantly during primary therapy (surgery and radiotherapy). For most patients, there was a 24 percent relative reduction in DNA load per radiotherapy visit. Yet, tumor-type HPV was detectable after treatment in14.3 percent of HPV-positive patients.

There was significantly lower two-year overall survival among the HPV-positive patients with persistent detection of tumor-type HPV after therapy versus patients without detectable tumor-type DNA after therapy (68 percent versus 95 percent). Similar results were seen for recurrence-free survival (55 percent versus 88 percent). Finally, among patients with detectable tumor-type DNA post-therapy, the cumulative incidence of recurrence by 2 years was 45.3 percent versus 12.2 percent among those without detectable tumor-type HPV DNA post-treatment.

“The clinical utility may be constrained by a need to identify the tumor-type infection, a low-moderate positive predictive value for recurrence, and weak associations with risk of distant metastases,” the authors caution. “Ongoing studies will evaluate whether multiplexed detection of plasma HPV DNA can improve these limitations.”

Takeaway: HPV DNA is detectable in oral rinse samples and holds promise for ongoing monitoring and surveillance of treatment response in patients with certain head and neck cancers. While feasible, additional research will be needed to determine the full clinical utility of this sample collection method.

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