Daniel, Jeannie

ABSTRACT Human papillomavirus (HPV) is comprised of >200 genotypes and has an ~8 kb, circular, double-stranded DNA genome. Transmission of HPV occurs through skin-to-skin contact and infection of squamous epithelial cells of cutaneous and mucosal surfaces. HPV genotypes are categorized as low- or high-risk (hrHPV) based on oncogenic potential. There are approximately 14 types of hrHPV that can cause several types of cancer, including HPV-associated oropharyngeal squamous cell carcinoma (HPV(+)OPSCC). Detection of HPV(+)OPSCC is traditionally accomplished using p16 immunohistochemistry (IHC) and HPV-specific testing, either DNA or RNA in situ hybridization (ISH) staining or DNA-based PCR of suspected tumor biopsy tissue. More recently, platelet-poor plasma (PPP) samples from patients with HPV(+)OPSCC have proven useful for detection and quantitation of fragments of HPV circulating tumor DNA (ctDNA). ctDNA has been shown to be useful in determining treatment response and monitoring for disease recurrence. In this study, a novel droplet digital PCR assay (ddPCR) was developed and validated for the detection and quantitation of ctDNA from 5 hrHPV genotypes in PPP. Analytical sensitivity ranged from 7.71 to 19.45 fragments of HPV ctDNA per milliliter of PPP across five hrHPV genotypes. In patients with confirmed primary or recurrent HPV(+)OPSCC or HPV(-)OPSCC, testing of corresponding PPP samples ( n = 32) by ddPCR demonstrated 90.63% (29/32) overall agreement with p16/HPV-ISH biopsy results. Compared with reference ddPCR assays performed at outside laboratories, our ddPCR assay yielded 90% (9/10) overall agreement. This assay may provide clinicians with a tool for monitoring HPV ctDNA prior to, during, and after treatment of an HPV-associated cancer. IMPORTANCE At least 14 genotypes of human papillomavirus (HPV) have been identified to have high oncogenic potential. While molecular diagnostic testing for HPV is widely available for liquid cytologic cervical samples, testing is limited for other sample types, including liquid biopsy samples, such as platelet-poor plasma (PPP). With the rising incidence of HPV-associated oropharyngeal squamous cell carcinoma (HPV(+)OPSCC), laboratory testing is an essential part of patient diagnosis, management, and surveillance. Here, we summarize the development and analytical performance validation of a multiplexed, droplet digital PCR (ddPCR) assay for the detection and quantitation of HPV circulating tumor DNA (ctDNA) in PPP. This assay may provide clinicians with a tool to address minimal residual disease for patients with an HPV-associated cancer.

ImportanceThe De-escalated Adjuvant Radiation Therapy (DART) phase 3 randomized clinical trial (RCT) showed that in patients with human papillomavirus (HPV)−associated oropharyngeal squamous cell carcinoma, postoperative minimal residual disease (MRD), detected through circulating tumor HPV DNA (ctHPVDNA), was associated with a higher risk of disease progression. When considered along with pathologic factors, postoperative ctHPVDNA assessment may improve patient selection for adjuvant treatment de-escalation; however, more data are needed to demonstrate how it may be used in personalizing treatment intensity.ObjectiveTo determine the association of postoperative MRD status with progression-free survival (PFS) after surgery for HPV-associated oropharyngeal squamous cell carcinoma.Design, Setting, and ParticipantsThis was a secondary analysis of the DART RCT, which was conducted from October 2016 to August 2020 in multiple sites in the US. Participants from the de-escalated adjuvant radiation therapy group and the standard of care group with available blood specimen data were included. Reports from 3-month posttreatment surveillance visits were used to assess associations and outcomes. Data analyses were performed from March 2023 to March of 2025.InterventionsThe DART group received 30 to 36 Gy of radiation therapy in 1.5 to 1.8 Gy twice daily, plus docetaxel, 15 mg/m2, on days 1 and 8. The standard of care group received 60 Gy with or without weekly cisplatin, 40 mg/m2.Main Outcome and MeasurePFS.ResultsThe analysis included 140 patients (mean [SD] age, 59.1 [8.4] years; 12 [8.6%] females and 128 [91.4%] males; 97 [69.3%] with no smoking history); characteristics were similar to the overall DART RCT population. Of these, 17 patients (12.1%) had postoperative MRD (13 of 96 [13.5%] receiving DART and 4 of 44 [9.1%] receiving standard of care). For all patients, postoperative MRD positivity was strongly associated with worsened PFS at 24 months (MRD positivity, 69.5%; MRD negativity, 95.9%; hazard ratio [HR], 0.19; 95% CI, 0.06-0.59). MRD positivity was associated with PFS when evaluating only those patients in the DART group, where 24-month PFS was 68.4% compared to 92.6% for MRD-negative patients (HR, 0.28; 95% CI, 0.08-0.93). Three months after completion of all treatment, 8 of 117 patients (6.8%) had detectable ctHPVDNA, whereas 109 of 117 (93.2%) did not, and detection was highly associated with PFS (HR, 20.48; 95% CI, 6.91-60.67).Conclusions and RelevanceThis secondary analysis of the DART RCT found that patients with detectable ctHPVDNA after surgery had a higher risk of disease progression. When added to the pathologic factors considered, ctHPVDNA assessment may improve selection of patients for treatment de-escalation. In addition, the 3-month posttreatment time point, early in surveillance, may identify a sizable portion of patients with progression and may guide intervention and surveillance after surgery for HPV-associated oropharyngeal squamous cell carcinoma.Trial RegistrationClinicalTrials.gov Identifier: NCT02908477