SAN DIEGO (FRONTLINE MEDICAL NEWS) – Endometrial cancer patients who regularly took low-dose aspirin experienced markedly better 5-year disease-free and overall survival compared to nonusers in an observational study, Dr. Koji Matsuo reported at the annual meeting of the Society of Gynecologic Oncology.

This apparent survival-prolonging effect of aspirin was greatest in women who were obese, less than 60 years old, had type 1 endometrial cancer, and/or received postoperative whole pelvic radiotherapy. In fact, the benefits achieved statistical significance only in patients who fit into one or more of these subgroups, added Dr. Matsuo of the University of Southern California, Los Angeles.

He presented a multicenter retrospective study of 1,687 patients with surgically staged endometrial cancer, 158 of whom were regular users of low-dose aspirin for various reasons, mainly cardioprotection.

The 5-year disease-free survival rates in aspirin users and nonusers were 90.6% and 80.9%, respectively. The 5-year overall survival rates were 96.4%, compared with 87.3%. Aspirin users had a higher cardiovascular risk profile. Their mean BMI was 36.7 kg/m2, versus 29.6 kg/m2 for nonusers. Moreover, aspirin users were also significantly more likely to have hypertension, diabetes, and hypercholesterolemia, and to be taking medications to manage those conditions.

In a multivariate analysis controlled for age, ethnicity, obesity, medications, tumor grade, stage, and histology, as well as the use of postoperative radiation therapy or chemotherapy, the adjusted 5-year risk of disease progression was 54% lower among aspirin users than in nonusers. The risk of all-cause mortality was reduced by 77%, according to Dr. Matsuo.

Aspirin’s mechanism of anti-oncogenic benefit in the setting of endometrial cancer is believed to involve its ability to inhibit COX-2, thereby curbing the chronic inflammation that figures prominently in the disease. Dr. Matsuo called attention to a recent retrospective cohort study by investigators at Montefiore Medical Center in New York. In that study, concomitant use of aspirin and a statin by endometrial cancer patients was associated with a robust 75% reduction in the risk of cancer-specific mortality, compared with women on neither (Obstet Gynecol. 2015 Jul;126[1]:144-50).

On the separate issue of whether aspirin is also useful for prevention of endometrial cancer, Dr. Matsuo noted that a recent Danish meta-analysis demonstrated a significantly reduced risk of developing the malignancy in regular users of aspirin, particularly if obese. The relative risk reduction in obese aspirin users, compared with nonusers, amounted to 44% in case-control studies and 20% in cohort studies (Gynecol Oncol. 2016 Feb;140[2]:352-8).

Discussant Dr. Kala Visvanathan commented that while the usual caveats about nonrandomized studies such as Dr. Matsuo’s apply – they must be considered hypothesis-generating rather than definitive because of the possibility of unrecognized confounders – repurposing an old drug such as aspirin as a treatment for cancer has enormous appeal.

The safety profiles and drug interactions of older medications such as aspirin, statins, and metformin are well established. And the ability to use an inexpensive older drug to simultaneously prevent or treat multiple common and serious diseases is a tantalizing prospect, observed Dr. Visvanathan, professor of epidemiology and oncology at Johns Hopkins University, Baltimore.