Healing process after breast cancer surgery could cause cancer to spread in mice, study says

While mastectomies and lumpectomies are common treatments used to remove cancer cells, the disease could return within months. Doctors may now understand why, according to a new report.

Researchers from the Massachusetts Institute of Technology conducted a study, published in Science Translational Medicine on Tuesday, to explore factors that may contribute to cancer recurrence post-surgery.

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To do so, they created a mouse model that mirrored patients with tumor cells in the breast. They found that the tumor incidence and size drastically increased, the authors wrote.

For further analysis, the scientists explored the immune system’s response during the healing process. It works to cure surgical scars by triggering cells throughout the body to help with the repair. However, in doing so, it may also recognize and rouse undetected tumor cells, causing cancerous ones to roam free and multiply.

Preeti Subhedar, breast oncology surgeon at Winship Cancer Institute of Emory University, told the Atlanta Journal-Constitution the findings were interesting.

"The exact mechanism of why some tumors metastasize and others don't is still not well understood, but this study adds some fascinating detail to the understanding of tumor dormancy," said Subhedar, who was not a part of the experiment.

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Subhedar stressed that the implementation of the sponge or any foreign object in animals is not the same as an actual tumor in humans.

“We don’t know if the immune response to a foreign object is the same as that to a tumor,” Subhedar said. “This study shows that there could be an association between the immune response and cancer spread, but an association is not causation.”

For the second part of the study, MIT researchers tested the effects of anti-inflammatory drugs, such as aspirin, as other studies have shown these medicines may help reduce the risk of other cancers, like colon cancer. Their method worked, and the mice developed "significantly smaller tumors than wounded, untreated mice," they said. In fact, the tumors often completely disappeared, and the medicine did not impede the mice's wound healing.

Although there is no definitive data on the relationship between anti-inflammatory drugs and cancer for humans, researchers are hopeful about the results.

“We have a lot more research to determine if and how surgery can influence cancer spread,” Subhedar said. “I hope that the public understands that these kinds of studies may provide interesting findings, but surgery still remains an important curative part of breast cancer treatment.”

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