Pre-emptive strike: Treating precancerous lesions may curb 'alarming surge' in nonmelanoma skin cancer

September 1, 2008

Treating actinic keratoses early is a must, as these can further develop into squamous cell carcinoma in situ and, in some cases, further complicate in field cancerization patients. Treating these lesions may help to reduce the surge in skin cancers, an expert says.

Key Points

According to one expert, treating pre-cancerous lesions is one way to possibly stem this trend.

Statistics show that the more actinic keratoses (AKs) a patient has, the more chance these AKs will develop into invasive squamous cell carcinoma (SCC).

"The choice of the agent, modality or combination therapy (for treating AKs) is dependent on the comfort level, individual physician practice style and patient variables," say Roger I. Ceilley, M.D., clinical professor of the department of dermatology, University of Iowa, Des Moines.

Topical therapies for actinic keratoses (AKs) are effective, with statistics showing that 5 percent 5-FU, 0.5 percent 5-FU, diclofenac and imiquimod achieve a complete clearance of lesions in 43 percent, 52 percent, 50 percent, and 45 percent to 50 percent of cases.

Previous studies

Topical imiquimod 5 percent cream applied three times a week is effective in the treatment of SCC in situ, with positive long-term clearance data. Dr. Ceilley says in those cases where imiquimod used as a monotherapy fails, a combination therapy of imiquimod and 5-FU can be very effective.

"These two topical therapies seem to work synergistically in SCC in situ lesions. The effects of 5-FU are enhanced by several of the cytokines induced by imiquimod, including INF-alpha, INF-gamma and IL-2," Dr. Ceilley tells Dermatology Times.

In field cancerization patients, the entire photodamaged area is often involved with clinical AKs, sub-clinical AKs, as well as foci of mutant clones of keratinocytes.

According to Dr. Ceilley, imiquimod can be ideally used in field cancerization patients with AKs, SCC in situ and superficial basal cell carcinoma (BCC).

Dr. Ceilley says photodynamic therapy (PDT) has proven itself in the treatment of field cancerization with AKs, SCC in situ and superficial BCC. The 5-aminolevulinic acid used in PDT therapy is a precursor of protoporphyrin, which selectively accumulates in the targeted tumor rather than in the normal skin.

"Though effective, PDT remains inferior to surgical excision and Mohs surgery for BCC.

"Furthermore, the risk of metastatic disease limits the use of PDT in invasive SCC. This therapy should be reserved for those patients who can not undergo surgical excision," Dr. Ceilley says.

According to Dr. Ceilley, imiquimod, as well as 5 percent 5-FU, can also be very advantageous in the treatment of superficial BCC consisting of five-times-a-week application for approximately four to six weeks, when application should cease at the erosion stage of the lesions.

At this time, a topical antibiotic ointment or petrolatum should be applied to the lesions until healed. Superficial BCCs can be treated with 5 percent 5-FU, twice a day for six weeks, but recalcitrant cases may need treatment for a total of 12 weeks.

Dr. Ceilley says nodular BCC can also be treated with topical imiquimod, with cure rates reaching 71 percent to 76 percent, and can be applied seven times a week for six to 12 weeks, depending on the balance between the level of intensity of reaction and the response rate.

Imiquimod and 5-FU are especially useful in elderly patients, and in young patients who are concerned with permanent scarring after surgery.

According to Dr. Ceilley, these topical treatments are especially effective and useful when used as an adjunct treatment to Mohs surgery, or following curettage and electrodessication treatment.

Retinoids

Dr. Ceilley says retinoids - used topically and orally - are currently being investigated and may prove very useful in future treatments of nonmelanoma skin cancers.