Individual-patient meta-analysis: Daily aspirin reduces risk for incident cancer with distant metastasis

Question: Does daily aspirin reduce risk for incident cancer with distant metastases or later metastasis? Review scope: Included studies were done in the UK and compared aspirin (any dose) with no aspirin for prevention of vascular events. Exclusion criteria were use of other antiplatelet agents unless given to both groups, < 10 incident cancers during follow-up, ≤ 90 days of treatment for acute vascular events, and treatment or secondary prevention of cancer or colonic polyps. Outcomes were incident cancer with metastasis at diagnosis or follow-up (excluding hematologic or primary brain cancers) and cancer mortality. Review methods: The selection criteria were applied to the search results from a companion review by Rothwell and colleagues (see adjacent page). Investigators were contacted, and national death certification and cancer registration records were reviewed. 5 randomized controlled trials (RCTs) met the selection criteria (n = 17 285, mean age 58 to 62 y, 29% to 100% men): 2 RCTs were for primary prevention of vascular disease, 1 for secondary prevention after recent vascular events, and 2 in patients with asymptomatic peripheral artery disease. Main results: Individual patient meta-analyses showed that daily aspirin reduced risk for incident cancer and death due to incident cancer (Table). Aspirin reduced risk for cancer with definite distant metastasis and increased risk for localized cancer (Table). Individual patient meta-analysis showed that aspirin reduced risk for metastatic adenocarcinomas but not metastatic nonadenocarcinomas (Table). Conclusion: Daily aspirin reduces risk for incident cancer with metastasis.