Prostate cancer linked to pesticides: Study

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Researchers at the University of Southern California (USC) have found an increased prevalence of prostate cancer among older men exposed to certain pesticides in Central Valley neighborhoods.

For their study the team used the state cancer registry to recruit 173 white and Latino seniors in Tulare, Fresno and Kern counties who had been diagnosed with prostate cancer between August 2005 and July 2006. They compared them with 162 men without prostate cancer, found through Medicare and tax records.

Researchers then traced where the men lived and worked from 1974 to 1999 and compared those locations with state records of pesticide application. Those who lived within 500 meters of places where methyl bromide, captan and eight other organochlorine pesticides had been applied, they found, were more likely to have developed prostate cancer.

“This is some evidence that we're doing a very bad job of controlling how you apply pesticides,” said Myles Cockburn, an associate professor of preventive medicine at USC's Keck School of Medicine who was among the authors of the study “Prostate cancer and ambient pesticide exposure in agriculturally intensive areas in California,” published this spring in the American Journal of Epidemiology.

Cockburn said they chose prostate cancer in part because, unlike other forms of cancer, the risk factors are relatively few. They chose to focus on residential rather than occupational pesticide exposure because of the Central Valley's demographics and because they suspected that previous studies were skewed toward those who handle pesticides, a population also more likely to have worn protective gear, he said. “California's Central Valley has by far the largest use of pesticides and the largest population potentially exposed to them in the United States,” he said.
The study was funded by the National Cancer Institute, National Institute of Environmental Health Sciences and Department of Defense Prostate Cancer Research Program.

Critics questioned the study's findings and definition of pesticide exposure. “Pesticide use doesn't equal pesticide exposure of bystanders,” said Robert Krieger, a toxicologist at UC Riverside, who said “contact with potential for absorption” would be more accurate. “Just because you lived in the vicinity of an application doesn't guarantee you were exposed,” Krieger said. He questioned whether the men involved in the study could accurately report details that might skew the results, such as whether they used household pesticides.

“The attempts to reconstruct exposure in retrospect is extremely uncertain,” he said, adding that he and other researchers have focused on workplace pesticide exposures that they can more easily quantify and trace.

Officials at the California Department of Pesticide Regulation had not reviewed the USC study Tuesday, but a spokeswoman defended efforts to guard against pesticide drift. “California's drift regulations are the toughest in the nation,” said Lea Brooks, a department spokeswoman. “They include buffer zones to address urban encroachment of agricultural lands and labor-intensive crops.” She said the department works with county agricultural commissioners to track pesticide drift, immediately investigate reports and issue civil penalties.

According to the National Institutes of Health, prostate cancer is the third most common cause of death from cancer in men of all ages and is the most common cause of death from cancer in men over age 75. Prostate cancer is rarely found in men younger than 40. The prostate is a small, walnut-sized structure that makes up part of a man’s reproductive system. It wraps around the urethra, the tube that carries urine out of the body.

This is not the first study to link pesticide exposure to prostate cancer. In 2008, University of California Davis Cancer Center research showed that Vietnam War veterans exposed to Agent Orange have greatly increased risks of prostate cancer and even greater risks of getting the most aggressive form of the disease as compared to those who were not exposed. Based on medical evaluations conducted between 1998 and 2006, the study identified twice as many men exposed to Agent Orange with prostate cancer. In addition, Agent Orange-exposed men were diagnosed two-and-a-half years younger and were nearly four times more likely to present with metastatic disease.

Use of prostate cancer therapy

A another new study featured in the newly released Journal of Urology dispels the myth that physicians' offices use prostate cancer treatments more often than hospital outpatient facilities.

The article, "Utilization Trends in Prostate Cancer Therapy," explains that as technology has improved, utilization of both surgical and radiation therapy for management of prostate cancers has increased. Specifically, the pattern increase for Intensity-Modulated Radiation Therapy (IMRT) for adenocarcinoma of the prostate, a common type of prostate cancer, in physicians' offices and hospital outpatient facilities is similar.

The principle author, Deepak A. Kapoor, along with a multi-disciplinary team of co-authors, sought to determine therapeutic trends in the management of adenocarcinoma of the prostate, particularly decision-making in surgery vs. radiation therapy, and whether site of service influenced those trends. The study demonstrated that the percentage of Medicare beneficiaries receiving treatment for prostate cancer has increased in recent years. Although there were increases in both surgery and radiation, the study demonstrated a clear shift toward minimally invasive surgery and newer technologies in radiation.

“Newer treatments, such as IMRT and robotic surgery, allow doctors to be far more precise and administer both surgery and radiation treatments with fewer side effects than older technology, which is why we've seen an increase in utilization by doctors in different settings,” said Dr. Kapoor, Chairman and CEO of Integrated Medical Professionals, and President-Elect of the Large Urology Group Practice Association. 

The In-Office Ancillary Services Exemption (IOASE) to the Stark Law, a Federal physician self-referral law, gives patients the option to be treated by their physician in their normal doctor's office. Some claim the IOASE causes utilization to be higher in physician offices than in hospitals.

But the study shows that the IMRT utilization patterns for Medicare beneficiaries were similar across physicians' offices and hospital outpatient facilities, increasing from 7.3 to 11.1 percent and 8.3 to 11.3 percent, respectively, from 2006-08 -- the most current data available at the time of the study.

Radiation and surgery treatments experienced 11.5 and 13 percent increases, respectively, from 2006-08. These trends show that patients are choosing safer, less invasive treatment options, such as IMRT and laparoscopic radical prostatectomy. 

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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