Effect of topical 5-fluorouracil treatment on actinic keratosis: a light and electron microscopic study

Evaluation of the efficacy and tolerability of 0.5% fluorouracil cream and 5% fluorouracil cream applied to each side of the face in patients with actinic keratosis

BACKGROUND

A new 0.5% fluorouracil cream has been developed that provides an alternative to the more highly concentrated topical formulations of fluorouracil that are currently available.

OBJECTIVE

This was a comparison of the tolerability and efficacy of the 0.5% and 5% fluorouracil creams in the treatment of actinic keratosis (AK).

METHODS

During this single-blind, randomized study, patients with > or =6 AK lesions were treated for 4 weeks with the 0.5% (once daily) and 5% (twice daily) fluorouracil creams applied to opposite sides of the face. After the end of treatment, patients were followed for an additional 4 weeks. Efficacy variables included absolute and percent reductions in AK lesions from baseline and total clearance of AK lesions. A questionnaire was used to evaluate patients' treatment preferences. Tolerability was evaluated through continuous monitoring of adverse events.

RESULTS

Treatment with 0.5% fluorouracil cream reduced the number of AK lesions from 11.3 at baseline to 2.5 at the end of the 4-week follow-up phase, compared with a reduction from 10.3 to 4.2 lesions after treatment with 5% fluorouracil cream. The reduction was significantly greater with the 0.5% cream compared with the 5% cream (P = 0.044). The 0.5% cream was as effective as the 5% cream in terms of the percent reduction in AK lesions from baseline (67% and 47%, respectively) and in achieving total clearance of AK lesions (both treatments, approximately 43% of patients). Both treatments were associated with similar degrees of investigator-rated irritation; however, patients preferred the 0.5% cream because they felt it was more tolerable (P = 0.003), easier to apply, and had a once-daily application schedule. Although all patients experienced facial irritation in association with both creams, fewer patients treated with the 0.5% cream reported symptoms of facial irritation.

CONCLUSIONS

In this study, 0.5% fluorouracil cream once daily was at least as effective as 5% fluorouracil cream twice daily in terms of the percent reduction in AK lesions and total clearance of AK lesions; it was more effective than the 5% cream in reducing the absolute number of AK lesions from baseline. Patients preferred the 0.5% cream to the 5% cream.

Destructive procedures are the standard of care for treatment of actinic keratoses

BACKGROUND

Actinic keratoses are premalignant lesions resulting from exposure to carcinogens. Recently, some Medicare carriers have limited reimbursement for destruction of actinic keratoses to those lesions unresponsive to topical 5-fluorouracil treatment.

OBJECTIVE

Our purpose was to determine whether this policy meets the community standard of care for treatment of actinic keratoses.

METHODS

Data from the 1993 and 1994 National Ambulatory Medical Care Survey were used to determine the frequencies at which different treatments are used for actinic keratoses. These were compared with the frequencies at which procedures and medical therapies are used to treat control conditions (warts, psoriasis, acne, and dermatitis) to determine whether procedures are done because they are available or out of medical necessity.

RESULTS

Procedures were performed during 78% of visits for actinic keratoses. 5-Fluorouracil was used at 3.6% of visits, and at 39% of these visits a procedure was also performed. There were no observations of use of 5-fluorouracil alone at a first visit for actinic keratosis. Procedures were less likely to be performed at visits for warts, psoriasis, acne, or dermatitis, which indicates that reimbursable procedures are performed not simply because they are available.

CONCLUSION

Procedures are performed to destroy actinic keratoses out of medical need. Medicare policies mandating initial use of 5-fluorouracil as initial treatment of actinic keratoses do not represent the community standard of care for treatment of these lesions.

Long-term efficacy and safety of Jessner's solution and 35% trichloroacetic acid vs 5% fluorouracil in the treatment of widespread facial actinic keratoses

BACKGROUND

Few studies have examined the long-term efficacy of fluorouracil (FU) or chemical peels for the treatment of actinic keratoses (AK). Our earlier work examined the efficacy and safety of a medium-depth chemical peel compared with the standard regimen of topical FU in the treatment of widespread facial AK through 12 months.

OBJECTIVES

To determine long-term efficacy of both treatments by extending our observations through 32 months.

METHODS

Fifteen patients with severe facial actinic damage were treated on the left side with a single application of Jessner's solution and 35% trichloroacetic acid and on the right side with twice daily applications of 5% FU cream for 3 weeks. Parameters evaluated at 1, 6, 12, and 32 months included counts of visible AK, random skin biopsies from both treatment areas, development of intercurrent neoplasms, and surveys assessing sun exposure.

RESULTS

Eight patients were available for reevaluation at 32 months. Both treatment sides showed a reduction in mean number of AK at 12 months followed by an increase in mean AK number between 12 and 32 months. Improvements in biopsies of clinically actinically damaged skin were seen in keratinocytic atypia, hyperkeratosis, parakeratosis, and inflammation at all treatment times during the study with both treatments. Three squamous cell carcinomas developed in the patients after initial treatment; one developed on the side treated with the peel, and two developed on the side treated with fluorouracil. Surveys failed to demonstrate an association between sun exposure and clinical response.

CONCLUSION

Based on these findings, patient with widespread actinic keratoses treated with medium-depth chemical peel or with 5% FU should be reevaluated yearly or every 1.5 years for reappearance of AK and retreatment.

Effect of 5-fluorouracil in cholesteatoma development in an animal model

This investigation was designed to evaluate the effects of the antimetabolite 5-fluorouracil (5-FU) on cholesteatoma formation in a chinchilla model. The animals received middle ear applications of propylene glycol according to a procedure previously shown to produce cholesteatomas in 60% to 70% of animals. A 5% solution of 5-FU was then applied to the lateral surface of the tympanic membrane (TM) and, after 1 month, temporal bones were taken for histologic study. No macroscopically visible cholesteatomas were present in any of the 16 temporal bones included in the study. However, microscopic invasion of epidermis to the medial side of the TM was observed in four specimens; perforations were present in three of these. Although there was considerable variability in the response to 5-FU application, the majority of specimens showed little or no proliferation of connective tissue in the lamina propria of the TM. In the four specimens in which epidermis reached the medial side of the TM, it did so either by migration through microscopic breaks in the fibrous layer or via TM perforations. Thus, 5-FU did not completely inhibit migration of epidermis into the middle ear. However, the results of this study indicate that it does tend to reduce the proliferation of TM epidermis and connective tissue, thereby reducing the likelihood of cholesteatoma formation in the experimental model.

Topical 5-fluorouracil treatment of superficial basal cell epithelioma. A light and electron microscopic study

A 27-year-old patient developed superficial basal cell epitheliomas approximately 20 years after taking Fowler's solution. One of the lesions was successfully treated with topical 2% 5-fluorouracil soultion under occlusion. Sequential biopsies of the lesion before, during and after therapy were examined by light and electron microscopy, and the changes at various stages are described. Changes occurred only in tumor cells and adjacent epidermis, and only after occlusion of 5-FU. After one week of occlusive therapy, focal discontinuities in the basal lamina and intercellular spaces were wider with reduction and condensation of tonofilaments. Mitochondrial degeneration was seen along with irregularities in nucleoli. These changes were most prominent after two weeks of occlusive therapy, and many degenerating keratinocytes were seen detached from other cells. One month after cessation of therapy, the entire area was excised, and no evidence of tumor was seen.