Of 45 included studies, 23 addressed the treatment of AK. Three of these were not discussed in detail as they were concerned with rarely used therapies.
No studies examined how different methods of treatment of AKs affected morbidity and mortality from SCC. There were no data on the efficacy of destruction, topical therapy, or other treatments to control AKs.
In two randomised trials, one in Texas (n=53; poor quality) and one in Australia (n=588; moderate quality), the daily use of sunscreen reduced the incidence of AK. In a subsequent, good-quality trial, sunscreen reduced the incidence of SCC by 18%.
One randomised trial evaluated the efficacy of a low-fat diet in controlling AKs (n=133; poor quality). In the first year, the control group was diagnosed to have four times as many AKs as the low-fat group. Over 2 years, patients in the low-fat group had a significant reduction in skin cancers.
Three randomised trials evaluated dietary supplements to prevent SCC and reduce the incidence of AKs. In one good-quality trial, beta-carotene had no effect on the incidence of AK or SCC. A randomised trial of a daily oral retinol supplement showed no effect in patients at high risk of SCC, but in a similar trial in moderate-risk patients, retinol reduced the incidence of first new squamous cell skin cancers by 32%. One case series reported that, in 70 patients followed for 1 year to 8.5 years, only 12 of 1,018 AKs treated with cryosurgery recurred.
One pilot study and two multicentre phase 3 trials examined the efficacy of photodynamic therapy. In the pilot study, the use of 10%, 20% or 30% ALA (aminolaevulinic acid) for photosensitisation was compared with placebo. Patients in all groups were exposed to the same light source after sensitisation. Significantly more AKs on the face and scalp or trunk and extremities responded completely to ALA than placebo.
Two multicentre trials found 88% of ALA-treated patients had at least 75% clearance of their AKs 3 months after initial treatment, versus 20% in the placebo group.
Five reports from four controlled trials and two case series examined the efficacy of 5-fluorouracil (5-FU). In these trials, 5-FU eliminated 75 to 80% of AKs initially present. In one study, the results of using 1% 5-FU and 5% 5-FU were similar. In some trials, a longer course of treatment was needed to treat AKs on the hand than on the face or scalp. One study compared the efficacy of tretinoin and 5-FU versus 5-FU alone on the upper extremity. The side treated with 5-FU plus tretinoin reduced the mean number of AKs per patient from 15.7 to 3.4. In the other two studies, tretinoin reduced the number of AKs more effectively than placebo.
One trial treated 427 patients who had 5 or more AKs per area of interest with topical diclofenac for 30 to 90 days. Assessment at 30 days after completion of treatment revealed that 39% of AKs on the forehead and 47% of AKs on the face were not visible, versus approximately 20% for the placebo group.
In one controlled trial, glycolic acid (a superficial chemical peel) reduced the mean number of AKs from 13.7 to 11.6 at 6 months. In another trial comparing two medium-depth peels, the overall improvement of AKs at 2 months was rated as 'fair - good' in those who had a peel with trichloroacetic acid (TCA) and glycolic acid, and "fair" in those who had a peel with TCA and Jessner's solution. In one controlled trial of 15 patients, a medium-depth peel with TCA was as effective as initial treatment with 5-FU.
One case series reported a 4% recurrence rate of AK at 6 months associated with 'cryopeeling'. At 2 years, this rate was 18%. Thirty-three patients developed SCC.
In a case series of patients undergoing dermabrasion, 22 out of 23 patients had no AKs after one year and 19 out of 23 had no AKs after 2 years. At 3 years, 15 out of 19 (64%) had no AKs. No SCCs were found. None of the studies used global or disease-specific measures to assess the impact of treatment on health-related quality of life.