A MULTI-INSTITUTIONAL analysis of circulating tumor DNA extracted from the plasma of patients has shown that human papillomavirus type 16 (HPV16) DNA is detectable in the majority of cases of favorable-risk HPV-associated oropharyngeal squamous cell carcinoma and may be a clinically useful biomarker of disease control in the setting of de-intensified chemoradiation therapy. These data were presented at the 2018 Multidisciplinary Head and Neck Cancer Symposium.¹ 

“Plasma circulating tumor HPV16 DNA may be a potential biomarker of tumor burden and also may be a window into tumor genomics.”

— Gaorav P. Gupta, MD, PhD

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“We found plasma circulating tumor HPV DNA reveals genetic heterogeneity among HPV-associated oropharyngeal cancer,” said lead author of the study, Gaorav P. Gupta, MD, PhD, Assistant Professor of Radiation Oncology and a member of the Lineberger Comprehensive Cancer Center at the University of North Carolina. “Unfavorable circulating tumor HPV16 DNA was strongly associated with regional disease failure in heavy smokers. Future studies will evaluate whether circulating tumor HPV16 DNA may help guide treatment intensity in nonsmokers and smokers.” 

As Dr. Gupta reported, previous studies have demonstrated that exposure influences risk in oropharyngeal cancer. HPV-positive patients, for example, generally tend to do well, whereas HPV-negative smokers tend to have poor outcomes.² However, the question remains whether genetic biomarkers can improve clinical risk stratification. 

“Plasma circulating tumor HPV16 DNA may be a potential biomarker of tumor burden and, importantly, response kinetics, because we can sample the blood quickly as these patients receive definitive and curative-intent treatment,” said Dr. Gupta. “It may also be a window into tumor genomics. Ultimately, we wanted to ask whether plasma circulating tumor HPV16 DNA may inform decisions on who is most appropriate for de-escalated therapy.” 

Dr. Gupta and colleagues developed a digital polymerase chain reaction assay for HPV16 DNA that is highly specific (does not cross-detect HPV18, HPV31, HPV33, or HPV35), linear (absolute quantification over five orders of magnitude), precise (exceptional reproducibility), and sensitive (detects as few as six copies of HPV16 with approximately 80% sensitivity). “We analytically validated this assay through a variety of means and are very encouraged by its performance as a potential diagnostic tool,” said Dr. Gupta. 

Interaction With Smoking History 

FOR THIS PROSPECTIVE, phase II clinical trial, investigators applied the assay to 64 patients with biopsy-proven, HPV-positive oropharyngeal squamous cell carcinoma. All patients received definitive chemoradiation therapy, and 54 patients (84%) enrolled in a prospective chemoradiation de-intensification trial, which consisted of 60-Gy intensity-modulated radiotherapy with concurrent weekly intravenous cisplatin (30 mg/m2). 

Following analysis of approximately 450 blood samples, the researchers identified 2 broad patterns of HPV DNA in the blood. In the first group of patients, pretreatment levels of HPV DNA in the blood were very high (between 257 and 22,684 copies/mL) and would drop to undetectable numbers after treatment. In the second group, lower pretreatment levels of HPV DNA spiked after initiation of therapy, likely reflecting increased distribution of tumor DNA as the tumor was receiving treatment, revealed Dr. Gupta. In both groups of patients, plasma circulating tumor HPV16 DNA would then diminish as therapy progressed, suggesting it was responsive to chemoradiation therapy and was largely cleared after treatment. 

Dr. Gupta went on to describe two distinct profiles of circulating tumor HPV16 DNA that correlated with smoking status and disease outcomes after chemoradiotherapy. Patients with abundant circulating tumor HPV16 DNA in the blood (at least 200 HPV16 copies/mL) and rapid clearance kinetics were deemed to have a favorable DNA profile. All other patients were deemed to have an unfavorable DNA profile, because they had delayed clearance kinetics, low copies of HPV16, variant HPV, or undetectable HPV in all five types (HPV16, HPV18, HPV31, HPV33, and HPV35). In both smokers and nonsmokers, the authors noted, approximately 30% of patients had favorable HPV plasma DNA profiles. 

“When we looked at regional disease control, determined by posttreatment neck dissection or regional recurrence in the field of radiation, we found that in patients who had a favorable circulating tumor DNA profile, smoking history did not have a measurable impact; there were no disease events in that cohort,” Dr. Gupta explained. “With unfavorable plasma DNA profiles, however, there was an interaction with smoking history.” 

As Dr. Gupta reported, heavy smokers with unfavorable circulating tumor HPV16 DNA (ie, patients with low/undetectable levels or delayed clearance) had “dismal” regional disease control and were strongly associated with regional disease failure. Patients with a limited smoking history, however, still had good outcomes, with 90% regional disease control. 

Francis P. Worden, MD

Potential Biomarker 

THE MODERATOR of the session, Francis P. Worden, MD, a medical oncologist at the University of Michigan Health System Comprehensive Cancer Center in Ann Arbor, noted the research was still in an early phase but may one day provide clinicians with valuable prognostic information. 

“These findings suggest the amount of circulating tumor HPV16 DNA in the blood as well as clearance kinetics could help stratify patients into low- and high-risk profiles,” said Dr. Worden. “It was interesting that unfavorable plasma DNA profiles had an interaction with smoking history.” ■ 

DISCLOSURE: Dr. Gupta has received research funding from the University Cancer Research Fund, Burroughs Wellcome Fund, Susan G. Komen Foundation, and the Department of Defense. Dr. Worden reported no conflicts of interest. 

REFERENCES 

1. Gupta GP, Kumar S, Marron D, et al: Circulating tumor HPV16 DNA as a biomarker of tumor genomics and disease control in HPV-associated oropharyngeal squamous cell carcinoma. 2018 Multidisciplinary Head and Neck Cancer Symposium. Abstract LBA1. Presented February 16, 2018. 

2. Ang KK, Harris J, Wheeler R, et al: Human papillomavirus and survival of patients with oropharyngeal cancer. N Engl J Med 363:24-35, 2010.