Cryotherapy No Better Than 50% Salicylic Acid, Costs More

Emma Hitt, PhD

September 27, 2011

September 26, 2011 — For the treatment of verrucae, cryotherapy using liquid nitrogen and patient daily self-treatment with 50% salicylic acid appear to result in similar efficacy outcomes, although cryotherapy is more expensive, according to the findings of a new randomized trial conducted in the United Kingdom.

Sarah Cockayne, MSc, from the Department of Health Sciences, York Trials Unit, University of York, United Kingdom, and colleague reported their findings in the September issue of Health Technology Assessment.

According to the researchers, it is estimated that almost 2 million people in England and Wales visit their general practitioner for the treatment of cutaneous warts each year, at a cost of £40 million. However, the "evidence base on which to inform clinical decision-making is poor," according to the authors. In addition, they note, a 2006 Cochrane review of 60 studies concluded that a trial comparing topical salicylic acid with cryotherapy was "urgently needed."

The current study, called the Effective Verruca Treatments trial, sought to assess the clinical effectiveness, acceptability, and cost-effectiveness of cryotherapy compared with salicylic acid for the treatment of verrucae.

A total of 240 study participants, all of whom were aged 12 years or older and had at least 1 verruca deemed treatable with either method, were included in the analysis. Participants were randomly assigned either to receive cryotherapy (n = 117), using liquid nitrogen, administered by a podiatrist, practice nurse, or general practitioner, or to treat themselves once a day with 50% salicylic acid (n = 123).

Cryotherapy was delivered by a clinician using liquid nitrogen in no more than 4 treatments at 2- to 3-week intervals. The first treatment involved a gentle freeze lasting approximately 10 seconds. Subsequent treatments, debridement, masking, and padding were given according to standard protocol used at the study site. Patients assigned to receiving 50% salicylic acid once daily for up to 8 weeks were instructed by a clinician about how to apply the treatment.

The proportion of patients with complete clearance of all verrucae at 12 weeks was comparable between the salicylic acid and cryotherapy groups (14.3% vs 13.6%; P = 0.89). The number of verrucae present was also comparable at 12 weeks (incidence rate ratio, 1.08; 95% confidence interval [CI], 0.81 - 1.43; P = .62). In addition, the percentages of patients who achieved complete clearance were similar between the groups at 6 months (30.5% vs 33.7% for the salicylic acid and the cryotherapy groups, respectively; P = .64). The time to clearance was also comparable for the 2 treatment groups (hazard ratio, 0.80; 95% CI, 0.51 - 1.25; P = .33).

Cryotherapy was more expensive than salicylic acid; the additional mean cost with cryotherapy was about £101 per patient.

Study limitations include the lack of a no-treatment group, which limited ability to assess spontaneous clearance of verrucae. In addition, the concentration of salicylic acid used is much higher than the dose usually used as first-line treatment (namely, over-the-counter concentrations of 15% - 26%); the 50% salicylic acid used in the current trial (also over the counter) may be considered second-line therapy.

"[T]here is very small probability of cryotherapy being cost-effective for a wide range of willingness-to-pay values," the authors conclude.

"The sensitivity analysis clearly demonstrates, primarily, the lack of treatment benefit of cryotherapy over salicylic acid and, secondly, that the larger number of treatment visits required for the cryotherapy drives the cost-effectiveness results," they add.

The project was supported by the National Institute for Health Research Health Technology Assessment programme. The 50% salicylic acid (Verrugon) plasters and felt pads were provided to the University of York, free of charge, by the manufacturer William Ransom & Son Plc. BOC Cryospeed provided liquid nitrogen storage equipment at reduced cost. Neither company has had any input into the design, analysis, and reporting of the study. The authors have disclosed no relevant financial relationships.

Health Technol Assess. 2011;15(32). Full text


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