Dec. 16, 1999 (Los Angeles) -- Compounds found in pesticides, food, and a variety of industrial products may be linked to a mutation frequently seen in patients with pancreatic cancer, say researchers in Spain. However, the lead author, Miquel Porta, tells WebMD that these results are preliminary and must be replicated before firm conclusions can be drawn.
Porta and his colleagues examined the levels of three types of compounds known as organochlorines in 51 patients with pancreatic cancer. They studied DDT, once commonly used in pesticides; DDE, a breakdown product of DDT; and substances known as polychlorinated biphenyls (PCBs), which are often used in making paint, electrical equipment, and other industrial processes. These compounds are also common in fish that have been contaminated. DDT has not been used in many years, Porta explains, but once in the body it can persist for decades, and DDE was found in a high proportion of the meat sampled in a recent study in Spain.
In their study, the investigators divided the patients, who came from five hospitals in eastern Spain, into two groups: 34 with a mutation in a gene known as K-ras, and 17 patients of the same age and sex who had a normal, or "wild-type," form of the gene. These patients were then compared with 26 patients chosen from a different hospital who were being treated for non-cancerous conditions.
To examine the relationship between pancreatic cancer, K-ras mutations, and organochlorines, the authors analyzed each subject's serum for DDT, DDE, and three kinds of PCBs. Serum concentrations of DDE and DDT were significantly higher in all 51 of the pancreatic cancer patients than in the other subjects, and cancer patients with K-ras mutations had significantly higher concentrations than cancer patients without the mutation. Patients with the highest levels of DDT were eight times more likely to have the mutation, and patients with the highest concentrations of DDE were more than five times more likely to have the mutation. PCB concentrations also were higher in the patients with cancer, and, as with DDT and DDE, concentrations of the PCBs were highest in patients with K-ras mutations.
Porta emphasizes that much more study is needed to illuminate the exact relationship among organochlorines, K-ras mutations, and the risk of pancreatic cancer. However, he points out that cigarette smoking is as yet the only well-established risk factor for pancreatic cancer, and it has not been linked to organochlorine exposure. Therefore, he says, this disease can be caused by more than one mechanism. However, while warning that "our study cannot directly answer the question" of the relationship between organochlorines and pancreatic cancer, he does point out that these compounds usually are found in fatty foods, and that "people seem to agree that the human body absorbs them more efficiently when they are dissolved in fat."
Porta emphasizes that this is only a small study, although "our results were statistically significant." Perhaps, he says, "this will open a new avenue for the study of K-ras mutations in pancreatic cancer. We looked at only one of the genetic alterations required for pancreatic cancer to develop. Now we must look at factors that influence the other genetic mutations that lead to this form of cancer."