Researchers from the Cancer Therapy & Research Center (CTRC) at The University of Texas Health Science Center at San Antonio and the University of Texas at Austin began by examining blood serum from breast cancer patients.
They placed the serum in a culture of fat cells that make estrogen, and then placed the serum on breast cancer cells.
The serum from overweight and obese patients caused the cancer cells to grow much more aggressively than the serum from patients who were not overweight.
"It looks like the mechanism is prostaglandins, which have a role in inflammation, and there's more of it in the obese patient serum," said CTRC oncologist Andrew Brenner.
Based on those findings, the researchers did a retrospective study on patients from the CTRC and the START Center for Cancer Care. They were segregated into those taking COX2 inhibitors (aspirin or ibuprofen) and those who did not.
"Patients who were on COX2 inhibitors tended to have a lower recurrence rate," Brenner said.
Anti-inflammatory use reduced the recurrence rate of ER positive breast cancer by 50 per cent and extended patients' disease-free period by more than two years.
ER positive breast cancers, cancers that grow in response to exposure to the hormone estrogen, are among the most common form of the disease, accounting for approximately 75 per cent of diagnoses.
The investigators have cautioned that these results are preliminary.
The findings are published in the journal Cancer Research.