oropharyngeal cancer

see also:

• neoplasia / cancer / tumours
• human papilloma virus (HPV)
• nasopharyngeal carcinoma

• 0.7% of men will develop oropharyngeal cancer (prior to widespread HPV vaccination)
• there appears to be 4 distinct groups of oropharyngeal cancer:
  • HPV infection (mainly HPV type 16) related:
    • now accounts for ~70% of oropharyngeal cancers
    • has the better 5 year survival rate (75-80% for stage III/IV), and accounts for over 60% of the tumours
    • expression of viral E6 and E7 oncoproteins that inactivate tumour suppressor proteins p53 and retinoblastoma protein (pRb), respectively, is necessary for malignant behaviour of these tumours
    • tobacco-related carcinogens may render HPV-positive tumours less responsive to Rx
    • ~7% of the adult population have oral HPV ¹⁾
      • 10% of men and ~4% of women have it
      • risk of oral HPV (prior to widespread HPV vaccination) ²⁾:
        • 15% of men if smoke and 5 or more oral sex partners
        • 7.4% of men who do not smoker but had 5 or more oral sex partners
        • 7.1% of men if smoke and 2-4 oral sex partners
        • 4% of men who do not smoker but had 2-4 oral sex partners
        • 1.5% of men who had less than 2 oral sex partners
        • 1.8% of female smokers who had less than 2 oral sex partners
        • 0.5% of female non-smokers who had less than 2 oral sex partners
    • 1% of the adult population have oral HPV type 16 which is associated with over 90% of oropharyngeal squamous cell carcinomas
    • it appears oral HPV infection is predominantly sexually transmitted
    • current smoking and intensity of smoking were independently associated with oral HPV infection, particularly among women
    • peak ages for oral HPV infection were 30–34 years and 60–64 years. This bimodal age pattern was particularly striking among men.
    • the number of HPV-positive oropharyngeal cancers diagnosed each year will surpass that of invasive cervical cancers by the year 2020
    • HPV-positive oropharyngeal tumours were increasing in incidence, now exceeding the number of these tumours caused by tobacco and alcohol abuse
  • hpv-negative, alcohol or cigarette related tumours:
    • 5 year survival rate 45-50% for stage III/IV³⁾
    • a 2013 study showed 55% patients with HPV-positive cancers were alive two years after a recurrence, compared with 28% of those with HPV-negative cancers
  • for oral cavity squamous cell carcinomas (OCSCC), two groups of no identifiable risk factor (NIRF), hpv-negative, no alcohol or tobacco, and probably mediated by endogenous factors⁴⁾
    • aging-related SBS1 endogenous mutation group
    • APOBEC-associated signatures (SBS2 and SBS13)