Despite remarkable treatment advances in childhood cancer in the past few decades that have resulted in a survival rate of more than 80% for childhood cancers in high-income countries, the survival rate among children with cancer in low- and middle-income countries can be as low as 10% in some settings,¹ with a wide variability in survival by cancer type. Limited options usually remain when the malignant tumor progresses after 1 or 2 lines of a standard chemotherapy protocol. Repetitive administration of conventional chemotherapy at the maximum tolerated dose imposes many adverse effects that further limit dosing and quality of life. The goal of the oncologist at this point remains mainly palliative, with an effort to halt the progression of cancer and improve quality of life. Often the only therapy offered is best supportive care, which includes treatment of pain and other associated problems without any definite therapy for cancer control.

PURPOSE: Hand-foot syndrome (HFS) is a dose-limiting side effect of capecitabine. Celecoxib prevents HFS by inhibiting cyclooxygenase-2 (COX-2) that is upregulated because of the underlying associated inflammation. However, systemic side effects of celecoxib have limited routine prescription. Topical diclofenac inhibits COX-2 locally with minimal risk of systemic adverse events. Therefore, we conducted this study to assess the efficacy of topical diclofenac in the prevention of capecitabine-induced HFS. METHODS: In this single-site phase III randomized double-blind trial, we enrolled patients with breast or GI cancer who were planned to receive capecitabine-based treatment. Participants were randomly assigned in a 1:1 ratio to receive topical diclofenac or placebo gel for 12 weeks or until the development of HFS, whichever occurred earlier. The primary end point was the incidence of grade 2 or 3 HFS (Common Terminology Criteria for Adverse Events version 5), which was compared between the two groups using simple logistic regression. RESULTS: In total, 264 patients were randomly assigned to receive topical diclofenac gel (n = 131) or placebo (n = 133). Grade 2 or 3 HFS was observed in 3.8% of participants in the diclofenac group compared with 15.0% in the placebo group (absolute difference, 11.2%; 95% CI, 4.3 to 18.1; P = .003). Grade 1-3 HFS was lower in the diclofenac group than in the placebo group (6.1% v 18.1%; absolute risk difference, 11.9%; 95% CI, 4.1 to 19.6). Capecitabine dose reductions because of HFS were less frequent in the diclofenac group (3.8%) than in the placebo group (13.5%; absolute risk difference, 9.7%; 95% CI, 3.0 to 16.4). CONCLUSION: Topical diclofenac prevented HFS in patients receiving capecitabine. This trial supports the use of topical diclofenac to prevent capecitabine-associated HFS.