Certain Pesticides Linked to Pancreatic Cancer Risk

Two French studies found that pesticide exposure increases the risk of pancreatic adenocarcinoma, the conventional form of pancreatic cancer. They were presented at the "Francophone Days of Hepatology, Gastroenterology, and Digestive Oncology" (Francophone Days of Hepatology, Gastroenterology, and Digestive Oncology). One, a case–control study, found increased risk among people with banned substances in their adipose tissue.

Increasing Incidence

Pancreatic cancer incidence has risen continuously for more than 30 years. Approximately 16 thousand new cases were reported in France in 2023, corresponding to an annual increase of approximately 2%. According to France's National Cancer Institute, "By 2030, pancreatic cancer could become the second leading cause of cancer-related death." Dr. Brugel said, "The increase is particularly high in France compared with other Western countries. The reasons remain unclear, raising the question of environmental factors such as pesticides," he said.

Pesticides are known to have mechanisms promoting carcinogenesis (cancer development). Their intensive use, particularly in France, is suspected of contributing to increases in some cancers. France is Europe's largest pesticide consumer, using 65 thousand tons annually, with 300 substances authorized.

Highest-Risk Regions

To explore the association, Dr. Brugel and colleagues conducted EcoPESTIPAC and PESTIPAC, presented at this year's conference. EcoPESTIPAC was a national ecological analysis dividing France into 5529 spatial units. Annual pancreatic cancer cases in each unit were identified through the National Health Data System.

Nine chemicals, including glyphosate, accounted for half of pesticide purchases in France. Total pesticide quantity was also examined regardless of molecule. Exposure over the 11 years from the start of 2011 to the end of 2021 was estimated using the median purchase rate per agricultural area.

More than 134 thousand cases were reported. Risk was elevated around Paris, central France and the Mediterranean basin, while western areas had the lowest incidence. This heterogeneous distribution suggests risk factors are involved. After adjustment for confounders such as smoking, the study found increased pancreatic cancer risk associated with total pesticide quantity and three specific substances: spray-form sulfur, mancozeb and glyphosate.

Risk Increase

A dose–response relationship was evident. An increase of 2.5 kg per hectare over 11 years raised pancreatic adenocarcinoma risk from 0.9% to 1.4%. "Although the increase is relatively small, remember that this risk applies across France," Dr. Brugel said. Risk appeared homogeneous across the country.

The first national study of this link found robust associations with the four identified factors but had limitations. Estimates of use were based on pesticide purchases.

PESTIPAC, the second study, was a case–control investigation at Reims University Hospital examining pancreatic adenocarcinoma in relation to organochlorine pesticide concentrations in fat and urine.

It included 26 patients with pancreatic cancer undergoing abdominal surgery, allowing collection of at least 10 g of fat. Morning urine samples were collected fasting.

Controls were 26 other patients undergoing surgery for benign abdominal conditions such as gallstones or hernia, allowing identical sampling. Groups were matched by age and body mass index, two pancreatic cancer risk factors.

Below is a mind map illustrating "Pesticides and Pancreatic Cancer" in the context of these studies:

Banned Substances

Chromatography and mass spectrometry tested 345 substances. Five banned substances were found in all patients, and nine in half the samples.

Brugel said, "Contamination is very common in both pancreatic cancer patients and controls," he said. Substances present in everyone therefore could not be compared between groups.

After adjustment, four fat-soluble substances were associated with increased pancreatic cancer risk: 4,4-DDE, mirex or perchlordecone, trans-nonachlor and cis-nonachlor. These four are herbicides banned for at least 30 years.

The study also examined whether pesticides in the body affected survival after pancreatic cancer. No significant difference was found in overall or disease-free survival.

Brugel said, "Pesticides are a plausible candidate to explain rising pancreatic adenocarcinoma incidence," he said. However, "although associations exist, they are not sufficiently understood, and clear causality is difficult to establish."

The researchers called for larger studies to confirm these associations. Assessing the general population's exposure to banned substances also appears warranted.