Aspirin Improves Survival in Colon Cancer Patients with Specific Tumor Type

Study finds aspirin improves survival outcomes only for patients with HLA class I antigen expression.

Use of aspirin as part of regular treatment in patients with colon cancer is associated with improved overall survival, but only if the patients’ tumors express a specific antigen, according to a study published online on March 31, 2014, in JAMA Internal Medicine.

Previous studies have found aspirin use after a colorectal cancer diagnosis can improve overall survival, but the new study finds that low-dose aspirin use appears to be associated with longer overall survival only when patients’ tumors express HLA class I antigen. In contrast, a low-dose aspirin regimen in patients with tumors that lost expression of the HLA antigen did not alter the survival outcome.

The researchers examined tissue samples from 999 patients who had surgery for stage III or lower colon cancer between 2002 and 2008, analyzing the samples for HLA class I antigen and the prostaglandin endoperoxide synthase 2 enzyme expression. They also looked at data on participants’ aspirin use after they were diagnosed with cancer.

There were 396 deaths in 817 aspirin non-users (48.5%) and 69 deaths in 182 aspirin users (37.9%) after diagnosis. Out of tumor samples from 963 participants that were analyzed, 320 showed a loss of the HLA antigen and 643 still had expression of the antigen.

In cases where there was a loss of the HLA antigen, 57 of 320 (18%) patients were aspirin users, while in patients with expression of the antigen, 122 out of 643 (19%) were aspirin users. The results indicated a strong benefit from taking aspirin in patients whose tumors expressed the HLA antigen, but not in patients whose tumors did not express the antigen.

Those with the HLA antigen who took aspirin after diagnosis had significantly increased survival, with an adjusted rate ratio of 0.53. By contrast, those without the HLA antigen who took aspirin after diagnosis had an adjusted rate ratio of 1.03.

“If the association of HLA antigen expression and benefit from aspirin is confirmed in other data sets it could be used in clinical practice, and our data may have important clinical implications for both the dose and timing of aspirin as an anticancer agent,” the authors write. “First, low-dose daily aspirin may suffice as an anti-metastatic therapy in patients with early-stage cancer. Second, because circulating tumor cells are found in the perioperative period, it could be argued that aspirin therapy should be initiated as soon as considered clinically appropriate after diagnosis.”

In an accompanying commentary on the study, Alfred I. Neugut, MD, PhD, writes that the negative health effects that come with taking aspirin outweigh its benefits in prevention of colon cancer. Dr. Neugut adds, however, that he would personally add aspirin to his treatment regimen if he were diagnosed with stage III colon cancer, so he would convey a similar message to his patients.

“Certainly, if one just simplistically does a back-of-the-envelope risk-benefit analysis of aspirin use vs chemotherapy, one must begin to wonder whether it is not time to make aspirin a part of the conventional standard of care for this disease, given the relatively low risk profile of aspirin,” Dr. Neugut writes.