Benefit of Topical Combination Therapy for Acne: Analyzing Effect Size Using Number Needed to Treat.

Background: Topical acne trials often are confounded by high vehicle response rates and differing outcome measures, making it difficult to compare treatments. Number needed to treat (NNT) can be a simple, clinically meaningful way to indirectly compare treatment options without head-to-head data. NNT is the number of patients who need to be treated with an intervention to observe one additional patient successfully achieving a desired outcome versus vehicle/placebo. While treatment attributes such as adverse events may not be captured, lower NNT is a good indicator of a more effective treatment.

Methods: Following a search of combination topical treatments for acne vulgaris, all treatments that reported pivotal trial efficacy data consistent with the 2018 FDA definition of success were included in NNT analyses.  Results: Of 13 treatments, 7 reported 12-week treatment success rates in 11 phase 3 trials, with similar baseline demographics/disease severity. Treatment success ranged from 26.8% with tretinoin 0.1%/benzoyl peroxide (BPO) 3% cream to 50% with triple-combination clindamycin phosphate 1.2%/adapalene 0.15%/BPO 3.1% gel. NNTs for the triple-combination gel were 4 and 5 (from 2 pivotal trials). Adapalene 0.3%/BPO 2.5% gel had an NNT of 5. Tretinoin/BPO had the largest range between trials, with NNTs of 4 and 9. The other 4 treatments had NNTs ranging from 6 to 8.

Conclusion: A comparison of combination topical acne treatment trial data, using the same treatment outcome and similar patient populations, resulted in triple-combination clindamycin phosphate/adapalene/BPO gel and adapalene/BPO gel having the most favorable NNTs.J Drugs Dermatol. 2024;23(2):42-49.  doi:10.36849/JDD.7927.