Disseminated superficial actinic porokeratosis: Diclofenac sodium gel could provide treatment

May 1, 2008

A small study shows that diclofenac sodium gel could provide an effective treatment for disseminated superficial actinic porokeratosis, although results so far suggest the drug may be better at preventing progression than clearing lesions, a study co-author says.

Key Points

Presently, very few effective treatment options exist for DSAP - a hereditary condition that is not that uncommon, especially in the South, says Raj Varma, M.D., a dermatology resident (and formerly a research fellow) at the University of Alabama at Birmingham (UAB), working under the supervision of Boni Elewski, M.D., vice chairman of dermatology at UAB.

However, it's somewhat difficult to assess the condition's true prevalence, Dr. Varma tells Dermatology Times.

"Often, it doesn't get biopsied, because DSAP lesions can be clinically diagnosed. But it's likely still underdiagnosed, overall," he says.

Sun exposure exacerbates both DSAP and actinic keratosis (AK), the latter of which consists of definitely premalignant lesions that eventually can transform into squamous cell carcinoma, Dr. Varma says.

"DSAP is thought to be a premalignant condition," he says, "but it's not known for certain if that's the case."

Although some physicians have reported cases of DSAP lesions transforming into skin cancer, he says, "Some patients can have these lesions for years, and they may not transform into anything malignant."

In the open-label pilot study, researchers at four sites enrolled a total of 17 adult patients with DSAP, which Dr. Varma notes is just one form of porokeratosis.

To confirm the DSAP diagnosis, researchers used biopsies or clinical evidence with documented family histories.

Patients applied diclofenac sodium 3 percent gel to a target area on one forearm twice daily for up to six months.

More specifically, researchers followed patients monthly for three months, and those who still had lesions in the target area at this point continued on the medication for an additional three months.

Investigators performed target- area lesion counts at each visit, as well as global lesion counts to assess each patient's natural progression or regression of overall disease.

They also instructed patients to avoid sunlight during treatment, and gave patients questionnaires at weeks 12 and 24 to assess their satisfaction with treatment.

Ultimately, 13 patients completed 12 weeks of treatment; 10 completed 24 weeks. A total of seven patients withdrew for various reasons, including adverse events (dermatitis, two patients), travel, family difficulties or lack of efficacy.

"We were hoping to gain from this study at least a fair improvement in the number of DSAP lesions. Overall, we found there was a slight reduction in DSAP lesions," but not enough to signify that diclofenac sodium is likely to provide a powerful treatment option in this regard, Dr. Varma says.

However, comparing target area lesion counts to global lesion counts suggested to investigators that the treatment could perhaps prevent or slow down the condition's progression, he says.

In particular, of the 13 patients treated for 12 weeks, seven experienced a decrease in target-area lesions, and one had a stable number of lesions.

Furthermore, seven patients showed an overall worsening of disease, as reflected through global lesion counts performed on all treated and nontreated areas.

More importantly, of the seven patients whose DSAP was progressing on a global level, six showed less progression in the target area than globally.

In the most dramatic case, one patient experienced a 79 percent decrease in target-area lesions versus a 47 percent global increase.

The 10 patients treated for 24 weeks showed similar results, says Dr. Varma. Three of these patients experienced a decrease in number of target-area lesions, and one had a stable number.

Nine of 10 patients exhibited an overall progression of DSAP in terms of global lesion counts, and of these nine, six showed less progressions on the target area compared to the global assessment.

Regarding patient satisfaction, questionnaires revealed mean ratings of four (on a scale of one to 10) for effectiveness and seven for comfort and elegance. Sixty percent of patients said they would use the medication again.

Because of the study's small sample size, it's impossible to derive statistically significant data from it, Dr. Varma says.

Accordingly, Dr. Elewski says that because she and her colleagues see numerous patients with DSAP, she is considering initiating a larger study with diclofenac sodium gel in the future.

Other study limitations include lack of a placebo arm and possible seasonal variation of DSAP, Dr. Varma says.

As it stands, he says, "We expected some improvement in DSAP, and we did see that improvement. It would have been nice to see a few more people with some definite clearing, but at least we showed that there was a trend toward some improvement."