The US Food and Drug Administration has approved a new treatment for some people with a very common form of skin cancer. Imiquimod cream, sold as Aldara, can now be used to treat superficial basal cell carcinoma.

However, it should only be used for people who are not good candidates for surgery, the standard treatment for this type of skin cancer. And it should only be used for cancers on the body, neck, arms or legs, not tumors on the face. The tumors should not be bigger than 2 centimeters (a little less than an inch) across.

The cream is applied once a day. In 2 studies, 364 patients used it 5 days a week for 6 weeks. Seventy-five percent of those patients had no evidence of cancer 12 weeks after treatment. In another study of 182 people, 79% showed no signs of the cancer 2 years after finishing treatment with Aldara.

Most people experienced skin irritation, including redness, swelling, peeling, itching, and burning, in the area where the cream was applied. The irritation went away after they stopped using the cream.

Skin cancer (both melanoma and non-melanoma) is the most common type of cancer in the United States. More than 1 million people develop non-melanoma skin cancer each year, and about 75% of those cancers are thought to be basal cell carcinomas.

People with fair skin are more likely to develop this type of cancer, as are people who spend too much time in the sun without adequate skin protection. Exposure to radiation or some chemicals may also increase risk.

Although basal cell carcinoma grows slowly and is not usually deadly, it does need to be treated to prevent it from growing into nearby tissues or bone.

Aldara, manufactured by 3M Pharmaceuticals, is also approved to treat genital warts and actinic keratosis, a precursor to a different type of skin cancer.