A history of allergies is associated with a lower risk of some cancers (including cervical, esophageal, laryngeal, colorectal) and possibly a higher risk of others (bladder, prostate). Allergies are a hyperactivation of the immune response and involve immune cell infiltration. A history of allergies may be inversely associated with the risk of some cancers either because of heightened immune surveillance, or due to effects of allergy symptoms themselves either ridding cancer causing agents from the body, or causing behavior modifications which reduce exposure to such agents. Few studies have investigated the relationship between a history of allergies and oral squamous cell carcinoma (OSCC). Of those, some failed to account for human papilloma virus (HPV) infection, which is a cause of some cancers and which may be associated with both OSCC risk and a history of allergy.
Dr. Marni Stott-Miller and colleagues in the Public Health Sciences Division tested the hypothesis that oral squamous cell carcinoma (OSCC) risk is lower in persons with a history of allergies. They also accounted for evidence of HPV infection, which they hypothesized would correlate with a weaker immune response (i.e. fewer allergies) and with increased OSCC risk. This is also the first study to distinguish between different types of allergens in OSCC, to further inform our understanding of the potential biological mechanisms.
Investigators included WA state residents 18-65 years old diagnosed with OSCC between 1985-1995 (n=400), as well as a comparison (control) group of persons of similar age and sex with no history of oral cancer (n=613), recruited by random digit telephone dialing. Participants answered questions about demographics, lifestyle, and medical factors prior to the reference date. (For OSCC cases, this was the date of diagnosis; for controls a date was randomly signed in a similar distribution to the cases’ diagnosis dates. Investigators used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs), and accounted for differences in age, sex, race, education, and history of smoking and alcohol use. Some analyses also accounted for differences in HPV infection status, and OSCC tumor site.
Cases were, on average, less educated, poorer, and more likely to be HPV positive compared to controls. Approximately half of controls had allergies, over 60% of which included allergies to dust, pollen, or mold. There was evidence for an inverse association between airborne allergens and OSCC (OR 0.67, 95% CI 0.48-0.93); there was no evidence for an association with other types of allergies. The airborne particle allergy association was limited to later stage OSCCs (regional or distant cancer at diagnosis) (OR 0.42, 95% CI 0.26-0.66) and was not observed in earlier stage cancers (in situ or local; OR 0.98, 95% CI 0.66-1.46).
The inverse association observed for later stage, but not earlier stage, OSCC supports the idea that persons with allergies are somehow also less likely to experience tumor progression/ promotion of early OSCC tumors (whereas an association with early stage tumors might suggest that allergies are associated with improved ability to prevent tumor initiation).
Possible explanations for these findings include the prophylaxis theory, whereby the allergy symptoms themselves remove cancer-causing agents from the oral and pharyngeal cavities, or that the allergy symptoms cause people to modify their behaviors, thereby reducing their exposure to potential cancer-causing agents. As authors point out, large studies using biomarkers are necessary to further investigate any biological mechanisms underlying the observed associations.