Bottom Line: An analysis of nearly 16,000 young patients with cancer in Utah revealed that exposure to fine particulate matter was associated with increased mortality at five and 10 years after diagnosis of certain cancers.
Journal in Which the Study was Published: Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research; this paper will be featured in a forthcoming Environmental Carcinogenesis Focus section in the journal.
Author: Judy Ou, PhD, research scientist at the Huntsman Cancer Institute at the University of Utah in Salt Lake City
Background: "It is estimated that roughly 40 percent of Americans live in communities with unhealthy levels of air pollution," said Ou. "Currently, there are no guidelines for long-term cancer survivors that advise reducing exposure to air pollution, nor are cancer patients considered a population vulnerable to mortality or illness from air pollution. Our results suggest that limiting exposure to fine particulate matter may be important for the survival of younger cancer patients with specific cancers."
Studies have shown associations between increased exposure to fine particulate matter, defined as atmospheric particles less than 2.5 micrometers in diameter, and cancer mortality among adult breast, liver, and lung cancer patients, yet the underlying biology of cancers in young patients potentially differs from cancers in adults, Ou explained. "Because the associations observed between exposure to fine particulate matter and increased cancer mortality in adults cannot be easily extrapolated to younger cancer patients, we wanted to study how continued exposure to fine particulate matter after diagnosis affected survival outcomes in this specific population," she said.
How the Study was Conducted: Using information from the Utah Population Database and Utah Cancer Registry, Ou and colleagues followed 2,444 pediatric (ages 0 to 14) and 13,459 young adult and adolescent (AYA; ages 15 to 39) patients diagnosed with cancer while living in Utah from 1986 to 2015. These patients were followed from diagnosis to the clinically relevant time points of five and 10 years after diagnosis.
To estimate cumulative exposure to fine particulate matter, the researchers used data from stationary monitors provided by the Environmental Protection Agency (EPA). Using this information, the researchers could model the association between cumulative exposure and mortality from cancer and all-causes. The exposure to fine particulate matter was measured continuously (in increments of 5 micrograms per cubic meter of air; μg/m3) and categorically (if exposure was equal to/exceeded the EPA annual standard of 12 μg/m3, based on the three-year average of annual mean concentration of fine particulate matter) for these models. Models were adjusted for sex, race/ethnicity, and socioeconomic status, among other factors.
Results: Among pediatric patients, exposure to fine particulate matter was associated with an increased risk of death for the following specific cancers:
- Lymphomas had increased cancer mortality and all-cause mortality at both time points, when exposure was measured continuously;
- Central nervous system and intracranial/spinal neoplasms had increased cancer mortality and all-cause mortality at both time points, when exposure was measured continuously;
- Lymphoid leukemias had increased all-cause mortality at five years post diagnosis, when exposure was measured both continuously and categorically;
- Hepatic tumors had increased all-cause mortality at 10 years post diagnosis, when exposure was measured continuously.
Overall, among AYA patients, exposure to fine particulate matter was associated with an increased risk of cancer mortality and all-cause mortality at both time points when exposure was measured categorically. Exposure to fine particulate matter was associated with an increased risk of all-cause mortality at five years post diagnosis when exposure was measured continuously.
Further, among AYA patients, exposure to fine particulate matter was associated with an increased risk of death for the following specific cancers:
- Central nervous system and intracranial/spinal neoplasms had increased cancer mortality and all-cause mortality at both time points, when exposure was measured both continuously and categorically;
- Skin melanomas had increased cancer mortality at five years post diagnosis when exposure was measured categorically and increased all-cause mortality at both time points when exposure was measured categorically;
- Carcinomas (excluding skin), when analyzed collectively, had increased cancer mortality and all-cause mortality at both time points when exposure was measured either continuously or categorically;
- Lymphomas had increased all-cause mortality at five years post diagnosis when exposure was measured categorically.
Author's Comments: "Exposure to air pollution is preventable to a degree on an individual level, but the responsibility ultimately lies with government policy to protect the public from this major health hazard," said Ou. "We need patients and their caregivers to become informed advocates to support enforcing air quality policies at the local, state, and federal levels."
Study Limitations: As a limitation to the study, data for 1999 to 2015 were collected from stationary monitors measuring fine particulate matter throughout the state of Utah, but the data for 1986 to 1998 were collected from stationary monitors measuring coarse particulate matter, defined as atmospheric particles less than 10 micrometers in diameter, in four Utah counties that contain 80 percent of Utah's population. "While fine particulate matter was not measured directly from 1986 to 1998, coarse particulate matter and fine particulate matter measurements are highly related, allowing us to extrapolate measures of fine particulate matter during these years," Ou explained.
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Funding & Disclosures: This study was sponsored by a grant from St. Baldrick's Foundation, grants from the National Institute of Health (NIH)/National Cancer Institute (NCI), and NCI's Geographic Management of Cancer Health Disparities program at the Huntsman Cancer Institute.
Partial support for all datasets within the Utah Population Database was provided by the University of Utah Huntsman Cancer Institute and the Huntsman Cancer Institute Cancer Center Support grant from the National Cancer Institute.
The Utah Cancer Registry is funded by the National Cancer Institute's SEER Program and the U.S. Centers for Disease Control and Prevention's National Program of Cancer Registries, with additional support from the University of Utah and Huntsman Cancer Foundation. Ou declares no conflict of interest.
About the American Association for Cancer Research
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