Sixty age-eligible participants were enrolled in the study with 30 participants in each treatment group. All of the participants completed the 26-week study period and were included in the intention-to-treat analysis. All of the participants were white with a median age of 67 years; the median number of baseline AK lesions was 12. Participant baseline demographics and clinical characteristics are provided in Table 1. Treatment compliance in both groups was good with only a few participants reporting missed doses.
In our evaluation of the rate of change in the number of AK lesions at week 8 compared to baseline, the 5-FU cream 0.5% group showed an 84% reduction in the number of AK lesions versus a 69% reduction in the control group. At week 26, the 5-FU cream 0.5% group showed a 72% reduction in the number of lesions versus 73% in the control group. There was no significant difference between 5-FU cream 0.5% and the comparator cream for either 100% or 75% clearance of AK lesions by the end of the study; however, comparing the AK lesion count from baseline to 8 weeks following the initiation of the study, participants in the 5-FU cream 0.5% group were more likely than the control group to achieve 75% or 100% clearance on the relative risk and risk difference scales (Table 2).
There were no significant differences between the 2 groups for the IGA of improvement at any time point (Table 3). On average, participants in the 5-FU cream 0.5% group experienced more dryness, erosion, fissuring, and redness than the control group but not more ulcerations by the end of week 4 (Table 4). All other QOL measures were statistically comparable between the 2 treatment groups for all time points.
A total of 25 AEs were reported throughout the study but none were considered to be serious. One AE (redness, burning, and itching over the eyebrow) was considered to be related to the study drug. No participants withdrew from the study due to AEs. A total of 12 participants in the 5-FU cream 0.5% group and 10 in the control group reported AEs.
After a 1-week course of 5-FU cream 0.5% following cryosurgery, a greater reduction in the number of AK lesions for a period of 2 months was noted in the treatment group compared to the control group. These findings are consistent with a similar study from 2006 that used 5-FU cream 0.5% or a vehicle 1 week prior to cryosurgery and then counted the number of AK lesions that remained.8 In the 2006 study, remarkable improvement out to week 26 was noted,8 unlike our study; however, there was insufficient power in our study to demonstrate a continued effect out to week 26.
Both the 2006 study and our current study support the benefit of using a combination treatment to clear AK lesions versus either treatment alone. Of note, these studies also show that combination treatments are equally effective, regardless of the order of treatments, in lowering AK lesion counts compared to cryosurgery alone.
Although participants in the 5-FU cream 0.5% group reported slightly more AEs on average at week 4, the rate of side effects was lower than those reported in a study documenting the side effects of a 4-week course of 5-FU.6 This rate of side effects must be considered in light of the added benefits this combination treatment has demonstrated.
Results of this pilot study suggest that a larger sample size would yield a difference in the study arms for all time periods (weeks 8 and 26). In an effort to maintain exchangeability of the study arms, patients were randomized at baseline treatment, but behaviors of patients in the 6 months following treatment, such as variation in sun exposure or other habits that promote AK lesion development, may have attenuated the results.
Key strengths of this study include no loss to follow-up and high medication adherence rates. The key limitation was the small sample size, which did not demonstrate a statistical advantage of the 5-FU cream 0.5% at 26 weeks; however, our study does show promise for larger future studies in illustrating this difference. A study by Krawtchenko et al9 noted that long-term efficacy of field therapy with 5-FU may ultimately be less than imiquimod cream 5%, suggesting that a possible alteration of the study protocol to compare the efficacy of different forms of field therapy may ultimately achieve better outcomes.
Overall, individuals with AK may benefit from a combination of treatment with cryosurgery and topical 5-FU to resolve lesions for longer periods than with cryosurgery alone. Although prior studies have found statistically significant differences in short-term and long-term treatment efficacy when cryosurgery is combined with an active field therapy versus a placebo vehicle,8,9 the current study aimed to find the best combination of efficacy with the fewest side effects. Therefore, the results of prior literature studies only further the feelings of the authors that with a protocol that looks at a slightly different treatment regimen within the treatment arm, the results can be extremely beneficial to patients. Further studies should be implemented to confirm the longer-term benefits of this combination therapy.
