Small Study Warns on Microplastics and Prostate Tumors

SAN FRANCISCO -- In tissue samples collected from patients with prostate cancer, microplastics and nanoplastics (MNPs) were present in almost every one, according to a small proof-of-concept study.

Among 10 patients who underwent radical prostatectomy, MNPs were found in 90% of tumor tissue samples and 70% of benign tissue samples using pyrolysis gas chromatography/mass spectrometry (py-GC/MS), reported Stacy Loeb, MD, of the NYU Grossman School of Medicine in New York City, and colleagues.

The study will be presented as a poster this week at the American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium.

"We already know that microplastics are everywhere, and in all kinds of tissues in the body," Loeb told MedPage Today. "So I guess it wasn't surprising that microplastics are in the prostate. But what was the most interesting finding, I think, was that the concentration was higher in the tumor than in the benign tissue."

The mean concentration of MNPs was 39.8 µg/g (median 16.3) in tumor tissue compared with 15.5 µg/g (median 7.0) in benign tissue.

Using Raman microspectroscopy, microplastic particles were detected in 60% of patient samples, with individual particles ranging from 1.2 to 40.3 µm in diameter.

While cautioning that the study was small, Loeb and colleagues said the results provide some evidence that exposure to microplastics could be a risk factor for prostate cancer.

Loeb noted that she and her colleagues were first inspired to conduct this study after a previous study among 304 Italian patients undergoing carotid endarterectomy showed that those with MNPs in their atherosclerotic plaque were 4.5 times more likely to experience myocardial infarction, stroke, or death.

"That got our attention about this topic and just how little evidence there is to date on the actual health impacts of microplastics," Loeb said. "But more and more data have been coming out showing the presence of microplastics in literally every organ and tissue of the body, like crossing the placenta, in the blood, in the brain. I'm a urologist and focus on prostate cancer, so I was wondering whether microplastics were found in prostate tissue and whether there could be any association with prostate cancer."

As for a possible mechanism behind a plastic-prostate cancer link, Loeb noted that the researchers in the previous study found that carotid plaques containing microplastics had more inflammation.

"And inflammation is certainly something that is associated with cancer development," she said. "So, we are planning to look at whether the concentration of microplastics was associated with higher levels of inflammation in those samples. Once we have more data, we're planning to stratify this by patients who have high-grade and low-grade tumors to get a better sense if the concentration is higher in higher-grade cancers."

Besides the small size of the study, Loeb and colleagues acknowledged that another limitation was the potential for MNP contamination during processing.

"It is very hard to study microplastics just because there's so much plastic in the operating room, in the pathology lab where it's processed, and in the laboratory," Loeb explained. Thus, the researchers designed workflows to minimize incidental plastic exposure, such as transporting specimens in aluminum containers and conducting plastic-free pathological evaluation.

However, "there's always the question of whether anything could have had contamination with plastic, since it can even be in the air, for example," she added. "Another reason I think that the finding that the concentration was higher in the tumor than the benign tissue is so intriguing is because these samples were processed exactly the same way. So, even if there was contamination from the air as the specimens were transported from the operating room or whatever, there would be no reason for there to be that differential between samples."

Of the 10 patients included in the study, median age was 65, median prostate-specific antigen level was 5.6 ng/mL, and 70% had intermediate-risk disease.

The researchers used visual inspection in tandem with Raman microspectroscopy to characterize particle abundance, morphology and chemical composition, as well as py-GC/MS to identify and quantify MNPs on a mass basis.

As for polymer types, nylon-6 and polystyrene were found above the method detection limit in the largest number of samples using py-GC/MS, while polyethylene and polyethylene copolymers were also identified on Raman microspectroscopy.