Key differences between HPV-positive and HPV-negative head and neck squamous cell carcinomas (HNSCC)
Head and neck squamous cell carcinomas (HNSCC) develop from the mucosal epithelium in the oral cavity, pharynx, and larynx and are the most common malignancies that arise in the head and neck.1 Increasingly, tumors in the oropharynx are linked to prior infection with oncogenic strains of human papillomavirus (HPV), primarily HPV-16 and, to a lesser extent HPV-18 and others.2,3 HNSCCs of the oral cavity and larynx are primarily associated with tobacco-derived carcinogens, excessive alcohol consumption, or both, and are collectively referred to as HPV-negative HNSCC.4 The median age of diagnosis for non-virally associated HNSCC is 66 years, whereas the median age of diagnosis for HPV-associated oropharyngeal cancer is about 53 years.5
HPV-positive and HPV-negative HNSCC are two distinct diseases with different sites of origin, etiological agents, risk factors, and contributions to the development of oropharyngeal squamous cell carcinoma (OPSCC). The demographics, cause, and prevalence of HPV-positive and NPV-negative cancers are summarized in Table 1.
Whereas the incidence of smoking-related HNSCC continues to decline worldwide, that of HPV-positive HNSCC is on the rise.6 During 2007-2016, HPV-associated cancers increased by 2.1% per year on average, whereas cancers not associated with HPV decreased by 0.4% per year on average.6
HPV-positive and HPV-negative HNSCCs present with different molecular characteristics, immune landscapes, and clinical prognosis (Table 2) and lead to two fundamentally different diseases with distinct pathogenesis in terms of gene expression, tumor microenvironment (TME), and mutational burden.
Genomic and epigenetic analyses reveal extremely high heterogeneity in HNSCC in terms of characteristic mutations, molecular signature, cellular phenotype, composition of TME, and immune landscape (Table 3).
Various promising vaccine targets have been identified and treatment options employed for the treatment of HPV-positive and HPV-negative cancers with varying degrees of success (Table 4).
Treatment personalization and de-escalation
According to Dr. Nishant Agrawal, Chief of Otolaryngology-Head & Neck Surgery UChicago Medicine, “We have seen a significant increase in the incidence of HPV-associated oropharyngeal cancer in relatively younger patients, with the median age of diagnosis in the 50s, even patients in their 30s.”32 He added that “Even at 2 years after radiation therapy, 15% of patients had grade 2 swallowing dysfunction and 8% had progressive dysphagia, so their swallowing is going to continue to get worse. Patients may also have chronic xerostomia. The dry mouth improves but it never gets back to 100%.”33 In contrast to patients with HPV-negative HNSCC, who have a five-year survival rate of about 25%-40%, patients with HPV-positive HNSCC fare much better with a disease-free survival rate of 85%-90% over five years. According to Dr. Agrawal, the better prognosis for HPV-positive patients suggests a need to de-escalate treatment while preserving survival.
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