Aspirin Fails to Stop Cancer's Return in Liver Metastasis Trial

The ASAC trial randomized 466 patients across 14 hospitals in Norway, Sweden and Denmark. Every participant had already been treated for colorectal cancer that spread to the liver, either by surgery or local ablation. They were assigned to take aspirin 160 mg daily or an identical placebo for up to three years. The results, published in The Lancet Gastroenterology & Hepatology, are blunt: aspirin did not reduce the risk of the cancer coming back.

"We found no benefit from aspirin in preventing cancer recurrence in these patients," said Sheraz Yaqub, professor at the University of Oslo and a consultant hepatobiliary surgeon at Oslo University Hospital. The aspirin group also showed lower overall survival, a finding the researchers say should be interpreted cautiously. Serious adverse events were more common among those taking aspirin. Yaqub's conclusion: aspirin should not be routinely recommended to prevent recurrence after curative-intent treatment of colorectal cancer liver metastases.

The stakes are high because roughly 30% of colorectal cancer patients develop liver metastases, and the metastatic disease is what usually kills. Surgery offers many of them their best shot at a cure, but the cancer still returns in more than half. Aspirin looked like a promising weapon: it's cheap, has been in use for over a century, and its effects and side effects are well documented.

The trial ran alongside the Scandinavian ALASCCA study, and both probed molecular changes in tumor tissue. ALASCCA found aspirin cut recurrence in some patients with localized colorectal cancer whose tumors carried specific alterations in the PI3K signaling pathway. ASAC found no benefit for liver metastasis patients, including those with the same molecular alterations. "What works for one group of patients does not necessarily work for another," Yaqub said.

An earlier registry-based study by Yaqub and colleagues, linking the Norwegian Cancer Registry with the Norwegian Prescription Database, had suggested colorectal cancer patients taking aspirin lived longer. He says such studies can only spot associations. "Randomized, placebo-controlled trials provide much stronger evidence about the effects of treatment," he said. Why the results diverged isn't clear yet, though differences in disease stage and tumor biology may be involved.

One thing patients shouldn't do is quit their own prescriptions. People already taking aspirin were excluded from ASAC, so the findings say nothing about them. "Patients who are already taking aspirin for cardiovascular disease or other medical indications should not stop treatment because of these findings," Yaqub said. Any change, he added, should be discussed with the treating physician.