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Cancer biopsy during colonoscopy doesn’t start new tumors

Kaiser Permanente clinical research finds patients who have a site biopsied after a cancer is biopsied are not more likely to develop a second cancer


A large Kaiser Permanente study should reassure patients that a biopsy of a cancer performed during a colonoscopy is highly unlikely to cause another cancer to start at other sites biopsied during the same procedure.

Douglas A. Corley, MD, PhD, research scientist, Division of Research, TPMG gastroenterologist.

“A previous study by a research group in the Netherlands had suggested this type of spread was biologically possible,” said the study’s senior author Douglas A. Corley, MD, PhD, a research scientist at the Kaiser Permanente Northern California Division of Research and a gastroenterologist with The Permanente Medical Group. “Our work shows this is not a common reason for people to get a second cancer.”

The new study, published May 26 in Clinical Gastroenterology and Hepatology, included 14,119 patients who had a cancer biopsied during a colonoscopy between January 2006 and June 2018. All of the patients went on to have their tumor removed.

In a review of the patients’ medical records, the research team identified 45 patients who were diagnosed with a new primary cancer between 6 months and 4 years after their first tumor was found. A new primary cancer is not the same as a cancer recurrence — which is when the original cancer comes back.

Our work shows this is not a common reason for people to get a second cancer.

— Douglas A. Corley, MD, PhD


These 45 patients were matched with 212 patients of the same age, race, and sex who had not developed a new tumor. Then, the researchers looked to see which of these patients had had another area of the colon biopsied after the cancer was found, and which had not.

In the patients who were later diagnosed with a new, second cancer, the researchers checked to see whether the biopsy and the new tumor were in the same place. Statistical analyses showed there was no significant association between having another area of the colon biopsied after the cancer was biopsied and the risk of developing a new tumor at the biopsied site.

“Metachronous colorectal tumors — new cancers found more than 6 months after the original cancer is found — are rare,” said first author Angela Lam, MD, a gastroenterologist with The Permanente Medical Group. “This means you need to be able to study a large number of patients to see if there is an association. Kaiser Permanente’s unique integrated care structure, the number of patients we treat, and our electronic medical record system make us one of the few places that could do a study like this to follow up on the previous findings.”

Angela Lam, MD, TPMG gastroenterologist.

The study from the Dutch research group, which was published in 2019, demonstrated through genetic tumor tests that it was biologically plausible to have a tumor seed, or start, a new tumor.

But even if 2 tumors are genetically similar, said Corley, that doesn’t mean the second tumor came from the first tumor. “When someone has colon cancer,” said Corley, “they are constantly releasing colon cancer cells into their colon. If someone has 2 tumors that are genetically similar, they may have both developed independently, due to the same factors. This is an area where we need more research.”

The real question, said Corley, is this: “Can cancer cells that get moved during a biopsy establish themselves in another part of the colon during a colonoscopy and start a new tumor at another biopsy site? And the answer to that question from our study is that this is not common — which is reassuring.”

The study was funded by the Population-based Research to Optimize the Screening Process (PROSPR 2) Consortium.

Co-authors include Jeffrey K. Lee, MD, MPH, from the Division of Research and The Permanente Medical Group; Sophie Merchant, MPH, and Christopher D. Jensen, PhD, of the Division of Research; and Mai Sedki, MD, formerly of the Division of Research.

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About the Kaiser Permanente Division of Research

The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 600-plus staff is working on more than 450 epidemiological and health services research projects. For more information, visit or follow us @KPDOR.

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