Aspirin’s benefits linked to HLA class I expression in colorectal cancer

Regular aspirin use doubled survival rates in patients with colorectal cancer whose tumor cells express human leukocyte antigen class I, according to study results presented at the European Cancer Congress.

“We think that platelets are involved in cancer spreading to other parts of the body by shielding tumor cells in the bloodstream so that they cannot be recognized by the immune system and can finally colonize distant organs,” researcher Marlies Reimers, MD, of the department of surgery at Leiden University Medical Center in The Netherlands, said in a press release. “Aspirin could help to ‘unmask’ those tumor cells by attacking platelet formation, so that the immune cells can detect and eliminate them.”

The analysis included 999 patients with colon cancer who were enrolled in the Eindhoven Cancer Registry between 1998 and 2007. Researchers evaluated all patients for expression of HLA class I and clyclooxygenase-2 (COX-2), as well as PIK3CA mutations.

Mean follow-up was 4 years.

Overall, regular aspirin use was associated with improved OS (HR=0.48; 95% CI, 0.22-1.03). However, use of other NSAIDs was associated with worse survival (HR=1.62; 95% CI, 1.18-2.23).

Among patients whose tumors expressed HLA class I, those who took low-dose aspirin — defined as 80 mg daily — after diagnosis were half as likely to die as those who did not use aspirin.

Aspirin’s effects were not linked to COX-2 expression or PIK3CA mutations, researchers wrote.

“HLA class I might serve as a predictive biomarker to help identify patients who could benefit from aspirin therapy after diagnosis,” Reimers said. “Although speculative, it may be that the interaction of platelets with HLA-positive tumor cells circulating in the blood promotes the metastatic potential of these cells. Aspirin interferes with this interaction, thereby decreasing the risk of metastatic disease and colon cancer-related death.”

For more information:

Reimers MS. Abstract #2183. Presented at: The European Cancer Congress 2013. Sept. 27 – Oct. 2, 2013; Amsterdam.

Disclosure: The researchers report no relevant financial disclosures.