The main purpose of this study is to determine the effectiveness of a new combination therapy for actinic keratosis. This study investigates a new indication for an FDA-approved topical medication, calcipotriol, for treatment of actinic keratosis, including how well it works and how safe it is when used in combination with the standard of care medication (5-fluorouracil) for the skin condition.

Inclusion Criteria:

• Age of at least 50 years
• Presence of four to fifteen clinically typical, visible, and discrete actinic keratoses in 25 cm2 on any of the four anatomical sites: scalp, face, right upper extremity and left upper extremity
• Ability and willingness of the patient to participate in the study (Informed consent is obtained)

Exclusion Criteria:

• Treatment area is within 5 cm of an incompletely healed wound or a suspected basal-cell or squamous-cell carcinoma
• Treatment area contained hypertrophic and hyperkeratotic lesions, cutaneous horns, or lesions that had not responded to repeated cryotherapy
• Recent (within a month) use of medications that could interfere with evaluation of the treatment area (e.g., topical medications, artificial tanners, immunosuppressive medications, immunomodulating agents, cytotoxic drugs, ultraviolet B phototherapy, other therapies for actinic keratoses, or oral retinoids)
• Premenopausal Women (to avoid any risk of pregnancy)
• History of hypercalcemia or clinical evidence of vitamin D toxicity