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

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.

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.

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.