Amanda Dilger

M.D.

Mass General Brigham

Surgeon (MEE)/Instructor - Otolaryngology-Head and Neck Surgery (Harvard)

PLCO (Learn more about this study)

PLCO-1381

Nov 13, 2023

A prospective study on air pollution exposure and incidence of aerodigestive tract cancer

It is well documented that compounds found in air pollution particles with a diameter less than 2.5 microns, or PM2.5 have carcinogenic capability, and substantial evidence has linked long-term exposure to PM2.5 with higher lung cancer incidence and mortality, particularly in non-smokers. Therefore, it is no surprise that the International Agency for Research on Cancer, or the IARC, has classified air pollution, particularly PM, as a causal agent (Group 1 carcinogen) for lung cancer.1 Recently, incidence in other types of cancer including of the breast, liver, pancreatic, and thyroid have also been associated with PM exposure, albeit with less robust and clinically significant data.

Considering the exposure of the upper aerodigestive tract to the same air pollutants as implicated in lung cancer, more evidence is needed on cancer incidence for head and neck cancer by subsite. Currently, there is limited evidence that links air pollution with head and neck cancer, particularly laryngeal, hypopharyngeal, nasopharyngeal and recently oral cavity cancer, however limited by small sample sizes, variable lag periods, and in some cases lack of controlled variables. Recently, however, PM2.5 levels were associated with selected cancer incidences using data from the Surveillance, Epidemiology, and End Results (SEER) U.S. cancer registry on a US county level with various lag models up to 15-years. Strong associations were made with PM2.5 exposure and lung cancer, and to a lesser extent oral cancer among other subsites. However, delineations between subsites were unclear, for example between oral and oropharyngeal and laryngeal and hypopharyngeal cancer incidences. Therefore, site specific incidence relationships to air pollution are still lacking, particularly for head and neck cancer.

This work primarily seeks to identify the association between PM2.5 exposure and the incidence of head and neck as well as lung cancers employing the Prostate, Lung, Colorectal and Ovarian (PLCO) trial data from the National Cancer Institute. Briefly, the PLCO trial assessed whether screening tests reduced deaths from prostate, lung, cervical and ovarian cancer. Participants were randomized to either control or screening including chest X-ray, flexible sigmoidoscopy, prostate-specific antigen screening, and digital rectal examination cancer antigen 125 screening and transvaginal ultrasound. This trial enrolled 155,887 men and women age 55-74 at 10 centers across the US between November 1993 and July 2001. The trial was funded by the National Cancer Institute with Clinicaltrials.gov numbers NCT00002540, NCT01696968, NCT01696981, and NCT01696994.