Aspirin as an Adjuvant Therapy in Colorectal Cancer

Aspirin use reduces the risk of colorectal cancer, and retrospective studies have suggested that aspirin use after surgery may reduce recurrence risk, particularly in patients with somatic PIK3CA mutations. Now, investigators report results from a double-blind, randomized, placebo-controlled trial of aspirin use (160 mg daily for 3 years) in 625 patients with resected stage I–III colorectal cancers harboring such mutations. Half had PIK3CA mutations in exon 9 or 20 (group A), and half had other moderate- to high-impact somatic variants in PIK3CA, PIK3R1, or PTEN (group B). About one third had rectal cancer, half had right-sided primaries, and a quarter had tumors with high microsatellite instability.

Key results were as follows:

• Patients receiving aspirin were half as likely to experience colorectal cancer recurrence by 3 years as those receiving placebo. This was true in group A (14% vs. 8% of patients), group B (17% vs. 8%), and the two combined.
• Subgroup analyses showed significant benefit in patients with rectal cancer and those receiving adjuvant or neoadjuvant therapy. Women appeared to benefit more than men.
• Serious adverse events occurred in 17% of patients receiving aspirin.