Whether aspirin may help prevent or reduce the risk of breast cancer remains a hotly debated research question. While past studies have indicated a potential benefit, most recently in hormone receptor-positive breast cancers, one new study from Penn Medicine suggests otherwise. Aspirin does not appear to be protective or associated with improved clinical outcomes or survival among breast cancer patients with aggressive disease, the researchers of one study report. However, another study suggests aspirin may in fact help reduce breast tissue density, which could lead to earlier detection of some breast cancers. Results of both studies will be presented at the 2015 San Antonio Breast Cancer Symposium (Abstracts PD1-04 and PD1-05, respectively) on Wednesday, December 9, 2015.

In the first study to report on the association of aspirin use with breast cancer outcomes in a large patient population, researchers examined the pattern of aspirin use, cancer pathology and overall survival in 1,000 patients treated at the Abramson Cancer Center of the University of Pennsylvania and diagnosed with breast cancers, including receptor positive, HER2- positive and triple negative cancers. A history of aspirin use for at least 30 days prior to diagnosis was reported in 14 percent of the participants.

The team, led Julia C. Tchou, MD, PhD, an associate professor of Surgery in the Perelman School of Medicine at the University of Pennsylvania, found that a history of taking aspirin was not associated with improved survival, regardless of receptor status. In fact, after a five-year follow up, researchers found that low-dose aspirin was significantly associated with worse overall survival compared to patients who didn’t take it before their cancer diagnosis.

The study’s first author Yun R. Li, a fourth-year MD/PhD candidate in the Perelman School of Medicine was chosen to receive an AACR Scholar-in-Training Award to attend SABCS based on her highly rated abstract by the Abstract Selection Committee.

The results come during a time when studies investigating aspirin’s anti-cancer effects have found evidence to support its benefit, beyond staving off cardiovascular disease or, in oncology, reducing the risk of colorectal cancer.

“Past studies have found that aspirin may hold anti-cancer benefits. However, many of them were preliminary, preclinical, and didn’t support a clear mortality benefit. They also didn’t look at prior use of aspirin,” Tchou said. “Our data did not support the notion that this century-old pill has protective qualities and down-the-road benefits for breast cancer patients. However, larger patient cohort studies are needed to confirm our results.”

In the second study, researchers examined whether aspirin is associated with breast density, which is a widely accepted risk factor for both estrogen receptor minus (ER-) and estrogen receptor positive (ER+) breast cancers, and can be a key factor in detecting tumors during routine mammograms.

Although some studies have suggested aspirin may help detect or prevent both ER- and ER+ breast cancers, clinical trials have yet to substantiate this effect.

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