Topical chemotherapy creams

Topical chemotherapy creams are applied directly to the skin to treat certain pre-cancerous skin patches and some very superficial skin cancers. The best-known example is fluorouracil cream, often called 5-FU cream, which is used for actinic keratoses, the rough, scaly patches caused by long-term sun damage, and for some thin, early skin cancers that have not grown deep into the skin. Because the medicine is absorbed only into the upper layers of the skin, very little reaches the bloodstream, so the whole-body side effects of chemotherapy such as hair loss and low blood counts do not usually occur. The cream is prescribed by a dermatologist or skin cancer specialist after the lesion has been assessed.

The important thing that people are often not warned about is the reaction. As the cream destroys abnormal cells, the treated skin usually becomes red, sore, itchy, crusted, weepy or even ulcerated for a period, sometimes looking much worse before it gets better. This inflammatory reaction is an expected sign that the treatment is working, not a sign of infection or allergy in most cases. The reaction can look alarming, especially on the face, and people who were not prepared often stop treatment early, which can leave abnormal cells behind. Once the course is finished, the skin heals over a few weeks, often leaving smoother, healthier-looking skin. Your doctor will explain how often to apply the cream, for how long, and what reaction to expect, and will usually review you during treatment. Always follow those instructions, and report reactions that seem severe, spread beyond the treated area or come with fever.

Apply only where prescribed

Use a thin layer on the areas marked by your doctor, avoiding eyes, lips and inside the nose.

Wash hands after applying

Wash hands thoroughly, or use gloves, so the cream does not spread to other areas or people.

Protect from the sun

Treated skin is very sensitive to sunlight. Cover up and avoid direct sun during treatment.

It cannot tell you whether a chemotherapy cream is suitable for your skin lesion. Many skin cancers need surgery or other treatments instead, and only a doctor who has examined the lesion, sometimes with a small sample of tissue, can decide.

It also cannot tell you how long to use the cream or how severe your reaction will be. Instructions and reactions vary by lesion, site and skin type.

Rare enzyme deficiency

People with a rare deficiency of the enzyme that breaks down fluorouracil can have severe reactions. Tell your doctor if you have ever reacted badly to this medicine.

Pregnancy

Chemotherapy creams should not be used during pregnancy. Tell your doctor if you are or might be pregnant.

Protect others

Avoid skin contact with others on treated areas, especially children and pregnant women.

Makeup and moisturisers

Ask before using cosmetics on treated areas. Gentle moisturisers may be allowed between applications.

Pain relief

Cool compresses and simple pain relief may help. Ask your doctor.

Social and work life

The reaction can be visible. Some people plan treatment for times with fewer social commitments.

Follow-up

Your doctor will check that the lesion has cleared and monitor for new ones.

Sun protection afterwards

Long-term sun protection helps prevent new sun-damaged patches.

How the cream works on abnormal cells

Fluorouracil interferes with the way rapidly dividing cells make DNA. Sun-damaged and pre-cancerous skin cells divide faster than normal skin cells, so they take up more of the medicine and are damaged more. As these abnormal cells die, the immune system clears them away, producing the redness, crusting and soreness that are part of the expected reaction. Normal surrounding skin is affected much less, which is why, after healing, the treated area often looks smoother and more even. Areas with more sun damage usually react more strongly, which can reveal patches that were not obvious before treatment began.

Managing the reaction day to day

During treatment, gentle care helps. Wash the area with plain water, pat dry, and avoid scrubbing or picking crusts. Cool compresses can ease burning. Your doctor may allow a bland moisturiser between applications, or a short break if the reaction is very strong. Wear loose clothing over treated areas on the body, and a wide-brimmed hat and shade for the face. If the reaction affects sleep or daily activities, ask your doctor rather than stopping on your own, as they may adjust the plan.

Other creams for skin lesions

Some skin lesions are treated with other creams that work through the immune system rather than as chemotherapy, and some need freezing, light treatment or surgery instead. Your doctor will choose the treatment that suits the lesion and your skin, and may combine or change treatments over time.

Photographs can help

Taking photos of the treated area every few days helps you and your doctor see how the reaction is progressing.

What to do next

Ask your doctor what the cream is treating and what reaction to expect, apply a thin layer only where prescribed, wash hands, protect from sun, complete the course unless advised otherwise, and seek help for spreading, infected or severe reactions.