Inclusion Criteria:

- Veteran who is at high risk for developing skin cancer defined as 2 keratinocyte
carcinomas in the past 5 years, at least one of which was located on the face or ears

Exclusion Criteria:

- Participants who are unable to speak English

- Participants with KC at randomization

- Participants currently using or having used field therapy for AKs on the face or ears
in the past 3 years. The vast majority of these field treatments would have been with
5-FU cream. We will allow recent use of therapies that are applied to individual AK
lesions (e.g. cryotherapy), but not those that were used on an entire area (field) in
the study treatment area Participants currently using or having used systemic
5-fluorouracil or oral capecitabine (Xeloda) within the past 3 years Participants
with known allergy to sunscreen, triamcinolone and/or 5-fluorouracil.

Exclusions 6-l0: We will exclude the small proportion who get their KCs for special
reasons other than ultraviolet radiation exposure (see list below), since that etiologic
difference, which is associated with a prognostic difference, could be associated with a
biologic difference in response to chemoprevention efforts. These will include:

- Solid organ transplant recipients, such as renal, hepatic, or cardiac transplant
patients

- Individuals with genetic disorders associated with very high cancer risk such as:

- basal cell nevus syndrome

- erythrodysplasia verruciformis

- xeroderma pigmentosum

- Arsenic exposure

- PUVA (Psoralen plus UVA) treatment

- Cutaneous T-cell lymphoma

- Prior or current radiation therapy to the face and/or ears.

Additional exclusions (12-15) are:

- Those who, in the opinion of the recruiting investigator, have very high mortality
risk at randomization (less than 50% chance of surviving 4 years) due to co morbid
illness such as metastatic cancer or COPD.

- For women of childbearing potential an initial pregnancy test and ongoing birth
control will be required for participation.

- Patients with known dihydropyrimidine dehydrogenase (DPD) enzyme deficiency by self
report or noted in the medical record (they have increased toxicity from systemic
5-FU, although screening for this is not part of dermatologic practice and will not
be part of this study).

- Patients on methotrexate (these will constitute about 1% of potentially eligible
individuals) because they may have more severe reactions to topical 5-FU.