Noninvasive biopsies may be faster and more effective for diagnosing HPV‐associated head and neck cancer

“We found that ctHPVDNA alone had excellent diagnostic accuracy. When we added physical exam and imaging findings into an algorithm with ctHPVDNA, this maintained high diagnostic accuracy and increased confidence in a non–tissue-based diagnosis.”—Daniel Faden, MD A new prospective, observational study finds that cell-free HPV DNA tests may diagnose HPV-HNSCC more accurately, at lower cost, and more quickly than tissue-based approaches. The study appears in Clinical Cancer Research (doi:10.1158/1078-0432.ccr-21-3151). According to the researchers, “HPV-associated cancers make up 5% of all cancers worldwide … HPV-HNSCC is the most common HPV-associated malignancy in the United States and continues to increase in incidence.” The goals of the study, says study author Daniel Faden, MD, an assistant professor in the Department of Otolaryngology at Harvard Medical School Massachusetts Eye and Ear, Massachusetts General Hospital, and the Eli and Edythe L. Broad Institute of MIT and Harvard in Boston, Massachusetts, were to compare the diagnostic accuracy of a ctHPVDNA-based diagnosis, combined with routine cross-sectional imaging and a physical examination, with the standard tissue-based clinical workup for the diagnosis of HPV-HNSCC. Additionally, the researchers investigated whether or not ctHPVDNA produced quicker results and lower costs than tissue biopsies using modeling. “This study is the first to evaluate a liquid biopsy-based noninvasive diagnostic approach for HPV-associated head and neck cancer and shows strong proof of principle to support such an approach, disrupting the existing dogma,” says Dr. Faden. The researchers recruited 70 consecutive patients diagnosed with HPV-associated oropharyngeal squamous cell carcinoma, nasopharyngeal carcinoma, or sinonasal squamous cell carcinoma at the Head and Neck Surgical Oncology Clinic at Massachusetts Eye and Ear between January 21, 2020, and March 30, 2021 (minus 4 months because of the coronavirus disease 2019 pandemic). Each candidate was at least 18 years old and agreed to contribute blood samples during a standard-of-care diagnostic workup. Only 61 of these potential participants qualified for the final analysis after 9 were excluded because they had not undergone direct HPV testing and did not have tissue available for testing or because they had already had at least partial treatment. The study's control group consisted of 45 patients who were diagnosed with HPV-negative HNSCC and 25 healthy individuals without cancer. For the liquid biopsy procedure, 10 to 20 mL of peripheral blood was processed for the collection of ctHPVDNA in plasma. The researchers designed and validated custom droplet digital polymerase chain reaction assays for DNA from HPV E7 genotypes 16, 18, 33, 35, and 45. The researchers also used modeling methods to compare liquid biopsy–based and tissue-based standard of care regarding the time to diagnosis (diagnostic interval) and the cost of diagnostic procedures (using fee schedules from the Centers for Medicare and Medicaid Services). In 61% (n = 37) of the patients eventually diagnosed with HPV-HNSCC, FNA of a lymph node was the first procedure for tissue sampling (surgical biopsy was the initial procedure for the remaining 39%). A diagnosis of HPV-HNSCC was successful in only 46% of the FNA specimens, in part because cystic necrosis of HPV-HNSCC nodal metastases can result in aspiration of nondiagnostic/inadequate material to perform confirmatory tests needed to make the diagnosis, such as p16 immunohistochemistry. In these cases, it was necessary to perform repeat FNA or surgical biopsy, which increased the cost and the time to diagnosis. In addition to these pre-analytic/specimen adequacy limitations, the researchers noted in their article that the “interpretation of p16 IHC on FNA specimens lacks consensus and is variable across pathologists and institutions.” The sensitivity and specificity of the noninvasive liquid biopsy approach were 98.4% and 98.6%, respectively, with positive and negative predictive values of 98.4% and 98.6%, respectively. The sensitivity and specificity of a combined approach using ctHPVDNA and criteria based on imaging plus physical examinations were 95.1% and 98.6%, respectively. The accuracy of this noninvasive approach was much higher than that of the traditional standard of care; the Youden indices (defined as sensitivity + specificity – 1) for the 2 approaches were 0.968 and 0.707, respectively (P < .0001.) Dr. Faden says that because using a standalone liquid biopsy for diagnosing HPV-HNSCC would lead to eventual treatment of that cancer, 100% specificity is necessary. “False positives would not be tolerated,” he says. “We found that ctHPVDNA alone had excellent diagnostic accuracy. When we added physical exam and imaging findings into an algorithm with ctHPVDNA, this maintained high diagnostic accuracy and increased confidence in a non–tissue-based diagnosis.” The study found that a large reduction in the time to diagnosis—an average of 26 days per patient—may be possible with liquid biopsies. This improvement is due primarily to the fact that scheduling patients for biopsies can add days or even weeks to the diagnosis in addition to the pathology processing time, whereas bloodwork can be obtained often on the same day or even ahead of time. “Importantly, time lag between presentation and treatment has been shown to be an independent predictor or survival in HNSCC,” they wrote. The researchers' cost modeling suggested that using a noninvasive approach with liquid biopsies may save more than $6000 on average in comparison with an approach based on FNA and/or surgical biopsies. “This study joins a host of others discussing the possibility of incorporating circulating tumor DNA into the diagnosis and monitoring of response to therapy in patients with head and neck cancer,” says Anurag Singh, MD, a professor of oncology and director of radiation research in the Department of Radiation Medicine at the Roswell Park Comprehensive Cancer Center in Buffalo, New York. In his experience, “delays in treatment due to the inability to make a diagnosis of HPV-positive head and neck cancer with routine procedures are rare. Following patients for recurrence after therapy, however, is fraught with significant costs and false positive tests. In this setting, liquid biopsy technology will certainly progress to allow routine follow-up on our patients' response to therapy with liquid biopsies. Ideally, the additional value to our patients would be to allow less onerous and less costly testing with fewer false positives and false negatives.” “The take-home message here for cancer researchers and clinicians is that a liquid biopsy-based diagnostic approach for HPV-associated head and neck cancer may have improved accuracy, reduced cost, and a shorter time to diagnosis compared to standard clinical workup,” adds Dr. Faden. “These findings suggest that this approach could be a viable alternative to traditional tissue biopsy in the future. The data for using ctHPVDNA detection in HPV-associated head and neck cancer are certainly growing, and I strongly believe that in the near future, ctHPVDNA will be how we diagnose and monitor all HPV-associated head and neck cancer patients. However, we must first generate more data from large, diverse patient populations and clinical settings, and review this data judiciously as a community, before adopting such an approach the standard of care. Specifically, we need more well-designed, prospective clinical trials testing ctHPVDNA compared to existing approaches.”