Efficacy of Switching from Prior Nonsteroidal Anti-inflammatory Drugs to Transdermal Diclofenac in Cancer Pain Management

<h3>Background/Aim:</h3> Nonsteroidal anti-inflammatory drugs (NSAIDs) are recommended for mild cancer pain and can be combined with opioids for moderate-to-severe pain. The efficacy of switching from prior NSAIDs to transdermal diclofenac in patients with cancer has not been fully evaluated, however. <h3>Patients and Methods:</h3> We conducted a retrospective observational study at the Cancer Institute Hospital, Ariake, Japan, from May 21, 2021, to May 20, 2023. Hospitalized of patients with cancer who were switched from prior NSAIDs to transdermal diclofenac were included. Patients were excluded if they never applied the patch, could not continue treatment for ≥7 days, or had dementia/delirium precluding pain assessment. The primary endpoint was change in numerical rating scale (NRS) score from baseline (Day 0) to Day 8. Statistical analyses were performed using the Wilcoxon signed-rank test, with <i>p</i>&lt;0.05 considered indicative of statistically significant differences. <h3>Results:</h3> A total of 72 patients were included. The median age was 67 years, and 46 were female. Prior NSAIDs included loxoprofen, flurbiprofen, naproxen, and celecoxib. Concomitant opioids were used in 55 patients. Mean NRS score decreased from 3.8 to 2.4 by Day 8 (<i>p</i>&lt;0.001). Forty-six patients (64%) showed reduced NRS scores. Rescue medication use decreased in 13 patients (18%), remained unchanged in 39 (54%), and increased in 20 (28%). One patient reported mild pruritus; no treatment discontinuation occurred. <h3>Conclusion:</h3> Switching to transdermal diclofenac effectively reduced pain in patients with cancer and may serve as a useful alternative when oral or prior NSAID therapy is difficult to continue.