The bad news: metastasis of breast cancer between 12 and 18 months after surgery could be attributed to a side effect of removing the tumors themselves. The good news: administering non-steroidal anti-inflammatory drugs – or NSAIDs such as aspirin or ibuprofen – could help prevent it from happening, writes a team from the Whitehead Institute for Biomedical Research in Cambridge, Mass., in the journal Science Translational Medicine.

“We find that the systemic inflammatory response induced after surgery promotes the emergence of tumors whose growth was otherwise restricted by a tumor-specific T cell response,” write the authors. “We demonstrate that perioperative anti-inflammatory treatment markedly reduces tumor outgrowth in this model, suggesting that similar approaches might substantially reduce early metastatic recurrence in breast cancer patients."

The researchers demonstrated the effect in mouse models. The mice were observed to have T lymphocyte cells – a key immune response – keep injected cancer cells from developing and spreading.

But when the mice were seriously wounded, natural immunosuppression took over, giving the cancer cells a window of opportunity.

“Inflammation induced during wound healing may disrupt this delicate balance,” say the researchers.

This domino effect is believed to be caused by an increase in inflammatory monocytes, which turn into tumor-associated macrophages. The macrophages suppress the T lymphocytes – giving the tumor cells sway.

The NSAID drug administered was meloxicam (brand name Mobic). The trials found that the drug prevented inflammation. In turn, mice subjected to the drug developed smaller tumors, some of which disappeared entirely. The process of healing the wound was not impeded, either, according to the paper.

The findings could essentially find a way to offset the risk of recurrence, the scientists said.

“Surgery is essential for treating a lot of tumors, especially breast cancer. But there are some side effects of surgery, just as there are side effects to any treatment,” said Jordan Krall, the first author, and a former postdoctoral researcher at Whitehead. “We’re starting to understand what appears to be one of those potential side effects, and this could lead to supportive treatment alongside surgery that could mitigate some of those effects.”

The post-surgical metastasis effect was previously documented in other studies, most notably a 2010 study by Belgian doctors.