Case-Control Study of Human Papillomavirus and Oropharyngeal Cancer

1. Case-Control Study of Human Papillomavirus and Oropharyngeal Cancer Osler Journal Club Shaline Rao, MD June 10, 2009

2. Background • HPV is the causative agent in nearly all cervical cancer • Molecular evidence has suggested HPV can be found in some oropharyngeal squamous cell carcinomas • No previous study has looked at the epidemiology of HPV infection and oropharyngeal carcinomas

3. Molecular Evidence • HPV 16 is found on pathologic examination of many squamous cell carcinomas of the oropharynx • HPV found in 26% of worldwide oropharyngeal carcinomas • Goal: Molecular evidence suggests a causal role for HPV in oropharyngeal carcinomas – does the epidemiologic evidence suggest the same?

4. Study Outline • Hypothesis: The epidemiologic data will suggest a relationship between HPV infection and oropharyngeal squamous cell carcinoma. • Study Design: Case Control Study • Setting: Johns Hopkins Outpatient Center ENT clinic • Participants: New diagnoses of oropharyngeal squamous cell carcinoma from 2000-2005 and matched controls • Data Collection: Cytopathology and serologic specimens + patient survey • Main Outcome: HPV is associated with oropharyngeal carcinoma in patients with and without traditional risk factors such as smoking and alcohol use. • Analytic Method: Unconditional and conditional multivariate regression models, odds ratios

5. Methods • Cases: All new diagnoses of oropharyngeal carcinoma (squamous cell) from 2000-2005 in the JHOC ENT Clinic • Controls: Patients seen in the same clinic during that time for benign conditions • 2 controls matched for each case based on gender and 5 year age range

6. Data Collection • Case: oral cytopathology obtained pre-treatment • Control: oral cytopathology obtained at enrollment • All patients filled a survey regarding oral hygiene, medical history, sexual history, demographics, family history, and use of tobacco, marijuana, and alcohol.

7. Laboratory Data • All cytopath specimens were tested for HPV16 • Subgroup of cases with +HPV16 were further assessed • Needed DNA in specimen to be at least 70% tumor • Serologic testing for exposure to HPV 16 was also performed in all patients to see if patients without HPV in their oropharynx had been exposed in the past

8. Statistical Methods • Alcohol and tobacco exposures were assessed as total life time consumption • Multivariate regression models were used to assess factors associated with HPV infection and subsequent oropharyngeal squamous cell carcinoma • This regression model is designed to reduce confounding by assessing each variable separately and together with the others to determine statistical significance

9. Results • 130 eligible cases- 100 agreed to participate in study • Cases who refused were more likely to be female • 70% of eligible controls participated in study (total of 200 patients) • Univariate analysis showed case and control patients were similar except cases were more likely to be from outside Maryland

10. Table 1

11. Table 1 Continued • Increase risk of oropharyngeal cancer if: • 1st degree relative with squamous cell head and neck cancer • Sibling with malignancy • Poor oral hygiene • Oral papillomas • > 20 pack year tobacco • Marijuana use • > 15 drinks per week x 15 years • Cases and control matched for use of ETOH, marijuana, tobacco, gender and age range

12. Table 2: Sexual History

13. Table 2 Continued • Increased risk of oropharyngeal cancer with: • High total lifetime number of partners • High total lifetime vaginal-sex partners • High total oral-sex partners • Suggests sexual exposure for HPV infection

14. Table 3 Increased risk of OP malignancy with oral HPV infection, and seropositivity for antibodies to HPV L16 capsid (validated measure of exposure to HPV).

15. HPV and Sexual Risk • HPV exposure was not enough to show significance between sexual behavior and oropharyngeal malignancy • However, patients with HPV16 + oropharyngeal malignancies were found to have history of higher vaginal / oral sex partners, infrequent condom use, and high total lifetime partners. • ETOH and tobacco cases also studied- those with HPV16 seropositive serum or oral HPV infection even w/o ETOH and tobacco had higher rate of oropharyngeal malignancy.

16. Table 4 Synergy of HPV16 exposure/infection, ETOH, and tobacco not found!

17. Tobacco and ETOH • In HPV seropositive patients there is no higher rate of squamous cell carcinoma based on exposure to ETOH or tobacco • In HPV seronegative patients, those with significant exposure to tobacco and ETOH did have higher rates of squamous cell carcinoma (not necessarily HPV related) than those who did not have exposure to tobacco and ETOH. • ETOH and tobacco are independent risk factors for squamous cell carcinoma of the oropharynx but not for HPV mediated malignancies.

18. Other Results • Factors associated with oropharyngeal carcinoma after controlling for sex, age, ETOH • HPV16 seropositivity – 55% of cases can be explained by this alone! • Poor dentition • Poor hygiene (infrequent brushing) • Tobacco use • First degree relative with squamous cell head and neck cancer

19. Pathology

20. Conclusions • HPV exposure has increased risk with risky sexual practices • HPV 16 L exposure observationally increases risk for subset of oropharyngeal cancer • HPV DNA can be found in nearly 72% of specimens for squamous oropharyngeal malignancy here at JHH • Tobacco and ETOH as independent but not associated risk factors for malignancy

21. Conclusions • Increased rates of oral sex and other sexual contacts resulting in HPV infection/exposure are associated with higher rates of squamous cell oropharyngeal cancer – in MEN and WOMEN • Consider vaccination for both genders for HPV, as this may reduce cervical and oropharyngeal cancers

22. Strengths • Methods to detect HPV are strong • Good effort made at matching to adequate number of controls • Given nature of study is epidemiologic and observational, case-control method is appropriate • Low cost study • Allows study team to use small numbers, patients with the target disease to be assessed for risk factors and long time frames retrospectively • Once enrolled, no loss to follow up or loss to sample • Public health implication for this study is important as it indicates good reason to vaccinate males for HPV

23. Weaknesses • Case control model – high risk for confounding and bias • Small cohort and clinic based based population • Low numbers of women, less than high school education, non white ethnic groups • This may not be most applicable study in our patient population • Cannot assess absolute risk with case control model • Bias may be introduced with selection of the controls • Variability in reporting by patients of their own behaviors (recall bias, deliberate underreporting) • Failure to recognize that they have oral/genital papillomas • Patients who refused the study may alter results in ways we are unable to recognize (selection bias) • Causality cannot be assumed in this case control model, only association

24. Discussion Points • Case Control Model – is there another model we could use that would better capture the intended data? • Cohort studies, prospective studies • Randomized trials involving active inoculation with HPV would be unethical • Public Health implications- the study focuses on the HPV implications and need for vaccination • What about other measures such as improved access to dental care, better education on dental hygiene, safe sex practices, and tobacco and ETOH cessation? • Note the baseline tobacco use is higher even in the controls! Should we do this study in a different or wider population? • If about 25% of oropharyngeal malignancy is HPV related, that leaves 75% to still be managed! • Which is the more cost effective and safe approach? • Perhaps we should be doing both!