Actinic keratoses are small, red, scaly spots that can feel like dry, sandpapery skin. They are a direct result of ultraviolet radiation, which is why they most commonly occur in sun-exposed areas, such as the face, forearms, and hands.

Why are actinic keratoses a concern? If left untreated, some actinic keratoses can develop into squamous cell skin cancers. Actinic keratosis can develop in almost 40% of white patients older than 50, making it the most common precancerous skin condition in this population. It is also one of the most common reasons for which people visit a dermatologist.

Field-directed treatments for multiple actinic keratoses

Cryotherapy, or the targeted use of liquid nitrogen, is commonly used to treat individual lesions. But what if there are many actinic keratoses scattered all over the face or hands? This is when field-directed therapy — using a treatment method to treat an entire area of skin — can be helpful.

There are several field-directed therapies available.

• A topical cream containing fluorouracil, a chemotherapy drug, works by disrupting DNA synthesis in and thereby destroying actinic keratosis cells. It can be applied at home and is typically used twice a day for two to four weeks.
• Topical imiquimod cream stimulates a local immune response in the skin, leading to destruction of the actinic keratosis cells. It can be applied at home and is typically used two to three times a week for up to 16 weeks, making this a longer course of treatment compared to topical fluorouracil.
• Topical ingenol mebutate gel injures two important components of actinic keratosis cells — mitochondria (the cells’ powerhouses) and plasma membranes (the cells’ gatekeepers) — leading to destruction of the cells. It is typically applied at home for three consecutive days. While convenient, many prescription plans do not cover this medication, making the out-of-pocket cost quite expensive.
• Photodynamic therapy uses light to activate a drug that is applied to the skin. This leads to destruction of actinic keratosis cells. This is an in-office procedure that is performed in one afternoon. It is a good option for those who prefer not to apply creams at home.

All of these therapies are frequently used by dermatologists, but there are no clear guidelines on which treatment is preferred.

New study compares effectiveness of field-directed treatments

An exciting study recently published in the New England Journal of Medicine sought to determine how effectively each of these four field-directed therapies treats multiple actinic keratoses. In this study, 624 patients with multiple actinic keratoses were randomized to treatment with one of the four aforementioned field-directed treatments.

The primary endpoint of the study was the percentage of patients who had at least 75% reduction in their number of actinic keratoses after one year. The study found that the percentage of patients who achieved this goal was significantly higher in people treated with topical fluorouracil (75%), compared to those treated with topical imiquimod (54%), photodynamic therapy (38%), and topical ingenol mebutate (29%).

This seminal study highlights the important role of field-directed treatment of actinic keratosis in decreasing a person’s risk of developing squamous cell skin cancers.

While this study found topical fluorouracil cream to be the most effective agent, other treatments may still have a role; each treatment has advantages and disadvantages in terms of time and cost, which may influence individual preferences. If you have multiple actinic keratoses, speak to your dermatologist to determine which treatment is the right choice for you.

Follow me on Twitter @KristinaLiuMD