MAL-PDT clears Bowen's disease with excellent cosmesis

National report - Photodynamic therapy using the topical photosensitizer methyl aminolevulinate 16 percent cream (Metvix, Galderma) is a non-invasive, well-tolerated, effective treatment for Bowen's disease, offering excellent cosmetic results, according to the findings of a multicenter, randomized, active- and placebo-controlled study, says Colin A. Morton, M.D., consultant dermatologist, Falkirk Royal Infirmary, Falkirk, Scotland.

The trial was conducted at 40 investigational sites across Europe and randomized 229 patients with 279 lesions 5:1:5 to: 1) PDT with application of methyl aminolevulinate cream (MAL-PDT); 2) PDT with placebo cream; or 3) standard therapy (cryotherapy or topical 5-fluorouracil 5 percent cream).

Responses were evaluated after three months, at which time a second course of treatment was allowed for partial responders (repeat treatment for patients in the placebo-PDT group was performed with MAL-PDT).

"Based on the results of this study and bearing in mind that Bowen's disease most often affects the lower extremities in older patients, topical MAL-PDT seems to offer an attractive therapeutic alternative deserving consideration as a first-line treatment option," Dr. Morton says.

He adds, "Previous studies have established the benefits of MAL-PDT for treatment of actinic keratosis (AK) and basal cell carcinoma (BCC), and now, with Bowen's disease added to its list of potential uses, MAL-PDT is emerging as a reasonable modality for dermatologists to consider incorporating in their practices."

The study

The study evaluating its role in the treatment of Bowen's disease enrolled males and females aged 18 years and older (mean age 73 years) who had a histologically confirmed diagnosis of Bowen's disease and lesions measuring 6 mm to 40 mm.

"This study and a previous trial using topical 5-aminolevulinic acid as the photosensitizer showed that PDT is a viable treatment for large lesions of Bowen's disease. In that regard, PDT will be important for helping to avoid the need for surgical excision and grafting, considering that the larger the lesion, the less likely it is to respond completely to other less invasive standard therapies," Dr. Morton says.

For the PDT treatments, MAL or placebo cream was applied three hours prior to illumination with a 570 nm to 670 nm red light source (prototype device from Photocure) at a dose of 75 J/cm². A second PDT treatment was performed one week later. For patients assigned to standard therapy, the choice between topical 5-fluorouracil (5-FU) and cryotherapy depended on availability and investigator's choice. Cryotherapy was performed to maintain the ice-field for at least 20 seconds. 5-FU was applied once daily for one week followed by twice daily for three weeks.

Results from the three-month assessment showed complete response rates of 93 percent for MAL-PDT, 21 percent for placebo-PDT, 86 percent for cryotherapy and 83 percent for 5-FU. The difference between MAL-PDT and placebo-PDT was highly statistically significant and there was a trend favoring MAL-PDT over the standard therapies.

Due to recurrences, complete response rates after 12 months had fallen in each of the active treatment groups. However, the complete response rate in the MAL-PDT group continued to be higher than among patients treated with cryotherapy or 5-FU.

"Topical chemotherapy and cryo-therapy are widely used and effective treatments for Bowen's disease as well as for AKs and BCCs, but their long-term efficacy has not been very well-studied. Therefore, the data collected on lesion recurrence in the MAL-PDT trials have been helpful for filling those knowledge gaps," Dr. Morton says.