Researchers are investigating whether pesticide exposure could help explain a puzzling increase in lung cancer among younger people who have never smoked, particularly women.
A preliminary study from the USC Norris Comprehensive Cancer Center found that lung-cancer patients aged 50 or younger reported eating more fruit, vegetables and whole grains—and generally had higher-quality diets—than the average American. The researchers stressed that healthy foods were not shown to cause cancer and that the possible role of pesticide residues remains unproven.
Unexpected Pattern Among Young Patients
Lung cancer has traditionally been associated with smoking, older age and male patients. The average age at diagnosis is about 71, and falling smoking rates have contributed to an overall decline in US lung-cancer cases.
However, that improvement has not been shared equally. Researchers say lung cancer has become more common among non-smokers aged 50 and younger, with women in this group now diagnosed more frequently than men.
To investigate the trend, researchers established the Epidemiology of Young Lung Cancer Project. The latest analysis involved 187 people who had been diagnosed with the disease by age 50.
Participants provided information about their diets, smoking histories, demographic backgrounds and diagnoses. Most had never smoked and had forms of lung cancer that differed biologically from the cancers commonly associated with tobacco exposure.
Previous work connected to the project also found that lung cancers diagnosed in people younger than 40 included distinct molecular subtypes compared with those generally found among older patients.
Patients Reported Healthier Diets
Researchers assessed participants’ eating habits using the Healthy Eating Index, which measures overall diet quality on a scale from one to 100.
The young lung-cancer patients recorded an average score of 65, compared with a US national average of 57. Women in the study generally received higher scores than male participants.
Participants also reported consuming more dark-green vegetables, legumes and whole grains than the broader population.
They ate an average of 4.3 daily servings of dark-green vegetables and legumes, compared with 3.6 servings among the typical American adult. Their average whole-grain consumption was 3.9 servings per day, compared with a national average of 2.6.
The findings initially appeared counterintuitive because diets rich in produce and whole grains are widely associated with better general health and a reduced risk of several diseases.
Lead investigator Dr Jorge Nieva said the pattern raised questions about whether an unidentified environmental exposure connected with food production—not the nutritional value of the foods themselves—could be affecting some younger adults.
Researchers Examine Pesticide Theory
The USC team believes pesticide residues may be one possible explanation requiring further investigation.
Conventionally produced fruit, vegetables and grains may carry more pesticide residues than many meat, dairy and heavily processed products. Researchers also pointed to earlier evidence associating long-term occupational pesticide exposure among agricultural workers with increased lung-cancer rates.
However, the study did not directly test the food eaten by participants or measure pesticide chemicals in their bodies.
Instead, researchers estimated potential exposure using previously published information about average pesticide-residue levels across food categories. This means the findings cannot establish that participants consumed unusually high pesticide levels or that such exposure caused their cancers.
The analysis also compared the eating habits of diagnosed patients with national dietary averages rather than following matched groups of people with and without cancer over time. As a result, the reported association should not be interpreted as proof that people who eat more fruit and vegetables face a higher lung-cancer risk.
Young Women Require Further Study
Women represented a particularly important group in the research because younger female non-smokers are experiencing lung cancer more frequently than men of the same age.
Female participants also tended to consume more fruit, vegetables and whole grains than male participants, giving researchers another reason to examine whether environmental exposures connected with produce may contribute to the gender difference.
Other established or suspected causes of lung cancer among people who have never smoked include second-hand smoke, radon, air pollution, asbestos and inherited or acquired genetic changes. The pesticide theory therefore represents only one possible explanation for a complex disease pattern.
Direct Testing Planned
The next stage of the USC project is expected to involve directly testing patients’ blood or urine for pesticide exposure.
Researchers hope laboratory measurements will reveal whether affected patients carry higher levels of particular chemicals and whether certain pesticides appear more strongly associated with lung cancer than others.
Nieva said identifying modifiable environmental contributors could eventually improve prevention strategies for younger adults. However, the team emphasised that substantially more evidence is required before public-health or dietary recommendations should change.
The research was presented at the annual meeting of the American Association for Cancer Research. Funding came from the Addario Lung Cancer Medical Institute, AstraZeneca, the Beth Longwell Foundation, Genentech, GO2 for Lung Cancer, Upstage Lung Cancer, the US National Institutes of Health and the National Cancer Institute.
The investigators disclosed that Nieva had received consulting payments from AstraZeneca and Genentech.
For now, the findings offer a possible direction for future research rather than a confirmed explanation. They highlight the need to investigate environmental exposures more carefully as doctors encounter increasing numbers of younger lung-cancer patients without a history of smoking.
