Hi everyone. Today I want to talk about the two topical therapies used to treat certain pre-cancerous lesions and early superficial skin cancers. The two creams are 5-fluorouracil (trade names efudex and carac) and imiquimod (trade name aldara). First, let's talk about these creams and then we will talk about how they are used, why they are useful, and what you should expect if prescribed these medicines.
5-fluorouracil is a chemotherapeutic agent used for various types of internal cancers in an intravenous form. When formulated as a cream, it is easily applied to the skin to treat certain cancers. This medicine works by disrupting the growth of cancerous cells. Cancerous cells are rapidly growing and dividing to form "daughter" cells and the 5-fluoruracil prevents the cancerous cells from be able to form offspring cells. The two available formulations, known as efudex and carac, are formulated at different concentrations and are used at different frequencies to achieve similar results. When using this cream, the area treated turns bright red and the skin actually looks worse before it clears up. This is an important point as the skin is visibly irritated during use.
Imiquimod is a newer agent used, like 5-fluorouracil, to treat skin cancers. It was originally approved for genital warts but is commonly used for skin tumors. (This fact usually surprises patients who are reluctant to purchase a cream known more for treating genital warts!) This cream, whose trade name is aldara, works by stimulating the immune system within the skin. This is the way it works for treating warts, although it is not completely clear if this is the same way it helps fights skin cancer. It likely stimulates the patient's immune system to fight off the cancer. This cream also makes the skin appear red and irritated while it is working to fight off the cancer and this clears up completely once the medicine is discontinued.
Both imiquimod and 5-fluorouracil are both used commonly to treat actinic keratoses, which are scaly areas of sun damage known to be precursors to squamous cell carcinoma. The usual treatment of these is to freeze them with liquid nitrogen. However, many people have too many of these lesions to freeze so the cream is applied to treat a large area without the pain of the liquid nitrogen. Treatment of actinic keratosis can range from daily use of 5-fluorouracil for several weeks to twice weekly use of imiquimod for several months to achieve similar results. Discuss with your dermatologist which type of treatment would best suit your needs. Any actinic keratosis that does not resolve after the treatment may need a biopsy to see if it is actually a skin cancer, and not a pre-cancerous lesion.
These creams can also be used for certain types of skin cancer and may be an alternative to surgery. Both imiquimod and 5-fluoruracil are also used for superficial basal cell carcinoma, which is an early and superficial skin cancer. Another type of basal cell carcinoma, known as the "nodular" type, may also be treated with these creams, although the efficacy is not as great as surgery. The earliest form of the squamous cell carcinoma is known as "in-situ squamous cell carcinoma", and these creams can effectively treat these lesions as well. Typically, the cream is applied to the cancer daily for 6 to 12 weeks although your dermatologist will dictate your course of treatment. The clear advantage of using the creams is that you will avoid surgery. However, the two disadvantages are the length of treatment (6-12 weeks of skin irritation from the creams) and it is difficult to be certain that the cancer is completely treated as there is no specimen sent to the lab to be evaluated by the pathologist. These are important considerations to discuss with your dermatologist.