Effect of Celecoxib vs Placebo as Adjuvant Therapy on Disease-Free Survival Among Patients With Breast Cancer: The REACT Randomized Clinical Trial.

Importance: Patients with breast cancer remain at risk of relapse after adjuvant therapy. Celecoxib has shown antitumor effects in preclinical models of human breast cancer, but clinical evidence is lacking.

Objective: To evaluate the role of celecoxib as an addition to conventional therapy for women with ERBB2 (formerly HER2)-negative primary breast cancer.

Design, Setting, And Participants: The Randomized European Celecoxib Trial (REACT) was a phase 3, randomized, double-blind study conducted in 160 centers across the UK and Germany testing 2 years of adjuvant celecoxib vs placebo among 2639 patients recruited between January 19, 2007, and November 1, 2012, with follow-up 10 years after treatment completion. Eligible patients had completely resected breast cancer with local and systemic therapy according to local practice. Patients with ERBB2-positive or node-negative and T1, grade 1 tumors were not eligible. Randomization was in a 2:1 ratio between celecoxib or placebo. Statistical analysis was performed from May 5, 2019, to March 5, 2020.

Interventions: Patients received celecoxib, 400 mg, or placebo once daily for 2 years.

Main Outcomes And Measures: The primary end point was disease-free survival (DFS), analyzed in the intention-to-treat population using Cox proportional hazards regression and log-rank analysis. Follow-up is complete.

Results: A total of 2639 patients (median age, 55.2 years [range, 26.8-86.0 years]) were recruited; 1763 received celecoxib, and 876 received placebo. Most patients' tumors (1930 [73%]) were estrogen receptor positive or progesterone receptor positive and ERBB2 negative. A total of 1265 patients (48%) had node-positive disease, and 1111 (42%) had grade 3 tumors. At a median follow-up of 74.3 months (interquartile range, 61.4-93.6 years), DFS events had been reported for 487 patients (19%): 18% for those who received celecoxib (n = 323; 5-year DFS rate = 84%) vs 19% for those who received placebo (n = 164; 5-year DFS rate = 83%); the unadjusted hazard ratio was 0.97 (95% CI, 0.80-1.17; log-rank P = .75). Rates of toxic effects were low across both treatment groups, with no evidence of a difference.

Conclusions And Relevance: In this randomized clinical trial, patients showed no evidence of a DFS benefit for 2 years' treatment with celecoxib compared with placebo as adjuvant treatment of ERBB2-negative breast cancer. Longer-term treatment or use of a higher dose of celecoxib may lead to a DFS benefit, but further studies would be required to test this possibility.

Trial Registration: ClinicalTrials.gov Identifier: NCT02429427 and isrctn.org Identifier: ISRCTN48254013.