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Actinic Keratosis (a.k.a. Solar Keratosis)

Key Points

  • Actinic keratoses (AKs) are the most common epithelial precancerous skin lesions.
  • They present as scaly, erythematous, ill-defined papules on sun-exposed areas.
  • A small percentage of AKs may progress to non-melanoma skin cancer (NMSC) over a lifetime.
  • Therapy is determined by anatomic location and number of lesions.

Introduction

Actinic keratoses (AKs) typically present as scaly, erythematous papules or plaques on sun-exposed areas, and are the most common epithelial precancerous skin lesions. Clinical variants of AKs include: erythematous, atrophic, hyperkeratotic, pigmented and lichenoid forms. AKs on the lower lip are termed actinic cheilitis. Treatment is necessary because approximately 2-15% of lesions may progress to non-melanoma cutaneous skin cancer (NMSC).

Three strategies for treatment are most frequently employed:

  1.  Physical destruction
  2.  Topical chemotherapy
  3.  Local stimulation of the immune system

Therapy is determined by location (face, scalp, forearms or legs) and extent (few versus multiple).

Initial Evaluation

Numerous actinic keratoses on sun-damaged skin are characterized by ill-defined hyperkeratotic erythematous papules or plaques. Actinic keratoses are commonly very thin and may lack erythema, and are best discerned clinically by palpation rather than visual inspection.

Actinic keratoses can present with a cutaneous horn, a column of hyperkeratotic scale lying over an ill-defined erythematous scaly papule.

General Principles of Actinic Keratosis Management

Initial therapy

Few lesions

First-line: Liquid nitrogen cryotherapy

  • Few or solitary lesions on any site are best treated with liquid nitrogen cryotherapy (a single application of 8-10 second thaw time).
  • Extensive lesions may also be managed by repeated cryotherapy.
  • A superficial treatment of the lips with liquid nitrogen cryotherapy is an effective treatment for actinic cheilitis.
  • Patients may experience erythema, edema, blistering, or eschar formation at sites of liquid nitrogen therapy that may last for 3-5 days after treatment. Sequelae and appropriate skin care should be discussed. Following cryotherapy, postinflammatory pigmentary changes (hypopigmentation or hyperpigmentation) can develop. (See patient handout Skin Care after Treatment of Actinic Keratosis.)

Multiple lesions

First-line: Numerous lesions are best treated with field treatment.

Available options for field treatment are:

  • Topical 5-fluorouracil (5-FU, 0.5-5%) cream or solution (such as Carac, Efudex, Fluoroplex)
Location Treatment with Length of treatment Additional notes
Face 1-5% cream b.i.d. or 0.5% microsponge cream daily 3 weeks Avoid eyelids and nasolabial folds
Lips 1-2% cream b.i.d. 3 weeks Reaction is more severe, painful
Arms, legs, scalp 5% cream b.i.d. 6-8 weeks May not be effective if thick scale is present
    • Warn the patient that they may experience swelling, erosions, and pain within 3-5 days after the start of treatment.
    • Brief interruptions in the treatment, such as taking the weekend days off during the treatment, may ameliorate these side effects and may increase patient compliance.
    • An intermediate potency topical steroid, such as hydrocortisone 2.5% cream or desonide 0.05% cream (such as Desonate, Desowen, LoKara, or Verdeso) b.i.d. may be used for several weeks upon completion of the therapy to alleviate erythema and inflammation. (See patient handout Skin Care after Treatment of Actinic Keratosis.)
    • Erythema may persist for up to 3 months following this therapy.
    • Close clinical follow-up in the following months is necessary to monitor for adequate treatment.
  • Topical imiquimod 5% cream (such as Aldara)
    • An alternative for treatment of lesions on the face and scalp, especially in patients intolerant of 5-FU
    • Apply three times weekly for 6 weeks or twice weekly for 16 weeks.
    • Patients should expect erythema, swelling, erosions, and pain within 1-2 weeks of initiating treatment.
    • As with topical 5-FU therapy, an intermediate potency topical steroid, such as hydrocortisone 2.5% cream or desonide 0.05% cream b.i.d. may be used for several weeks upon completion of the therapy to alleviate erythema and inflammation. (See patient handout Skin Care after Treatment of Actinic Keratosis.)
    • Follow-up in the following months is necessary to monitor for adequate treatment.
  • Photodynamic therapy (PDT)
    • PDT is a newer treatment in which a topical photosensitizer (i.e., methyl aminolevulinate, such as Metvixia, or 5-aminolevulinate, such as Levulan) is applied to the skin in the medical office 30-60 minutes or 3 hours (depending on which photosensitizer is used) prior to exposure to a light source for approximately 10-15 minutes.
    • Several different light sources are currently available for the treatment of AKs:
      • Aktilite 630nm
      • BLU-U 417 nm
      • Other light sources can be used emitting in red light with a continuous spectrum of 570-670 nm
    • PDT is indicated for actinic keratosis, actinic cheilitis, and some other non-melanoma skin cancers.
    • Referral to a dermatologist is recommended.

Subsequent therapy

  1. Educate patients on the cause and natural history of AKs.
  2. Instruct the patient to avoid excess sun exposure and apply a sunscreen daily. There is emerging data to support that regular sunscreen use may help prevention of non-melanoma skin cancer, including AKs, in certain individuals. (See patient handout Choosing a Sunscreen.)
  3. In the future chronic application of tretinoin 0.02-0.05% cream may be indicated as a topical chemopreventive agent.
  4. Routine follow-up evalution every 3-6 months to examine the skin carefully for AKs and other cutaneous cancers.

When to refer for dermatologic consultation

  • If dermal induration is present and/or if the diagnosis of actinic keratosis is not clear. The most serious error is misdiagnosing a basal cell carcinoma or squamous cell carcinoma, with resultant inadequate treatment and possible metastasis.
  • Recurrent actinic keratoses despite treatment
  • Multiple lesions requiring field treatment such as topical chemotherapy or PDT.
  • Actinic keratoses in the setting of immunosuppression (organ transplantation, HIV).

Clinical Cases

Case 1

Few lesions of actinic keratosis

  • 72-year-old woman presents with a 3-month history of several new lesions on the dorsal hands
  • She reports increasing scale and crusting of the lesions, noting that the crusting sloughs intermittently (but then recurs)
  • No prior history of skin cancer
  • History of extensive sun exposure during her youth and early adult life
  • A complete skin exam reveals no additional suspicious lesions

Initial treatment

  • Liquid nitrogen spray (thaw time 8 seconds)
  • Liquid nitrogen can be applied by: Application by cryo spray; use of a specialized plastic cone or otoscope piece may aid in focusing the spray at the base of the lesion Application of cotton swab dipped in liquid nitrogen to lesion Application of metal forceps dipped in liquid nitrogen to base of lesion
  • Counseling of sequelae and skin care after treatment
  • Follow-up in 6-8 weeks

Follow-up evaluation at 8 weeks

  • Lesion has been completely eradicated, with only faint macular erythema; here no induration or scale present
  • Photoprotection counseling
  • Follow-up for skin exam in 6 months

Case 2

Multiple actinic keratoses

  • 83-year-old woman presents for follow-up of actinic keratoses; her lesions have been previously treated with liquid nitrogen therapy
  • No prior history of skin cancer or melanoma
  • History of extensive sun exposure during her youth and early adult life
  • A complete skin exam reveals numerous ill-defined, erythematous scaly papules on the face in a photodistributed pattern without induration or nodularity

Initial treatment with topical chemotherapy

  • Recommend field treatment with topical 5-FU cream (5%) applied b.i.d. for 3 weeks. After the 3 week treatment, the patient is instructed to use desonide cream (0.05%) b.i.d. to reduce irritation and inflammation.
  • Sequelae and skin care during/after treatment discussed.
  • Photoprotection emphasized.
  • Follow-up evaluation at 6 weeks.

Follow-up evaluation in 6 weeks

  • Two lesions remain on the forehead; they are scaly, erythematous papules without induration or nodularity; they are treated with liquid nitrogen therapy; the remaining lesions have resolved with faint persistent erythema
  • Photoprotection counseling
  • Follow-up for skin exam in 6 months

References

Cowen EW, Nguyen JC, Miller DD, et al (2010) Chronic phototoxicity and aggressive squamous cell carcinoma of the skin in children and adults during treatment with voriconazole, JAAD, 62(1):31-37.

Criscione VD, Weinstock MA, Naylor MF, et al (2009) Natural history and risk of malignant transformation in the Veterans Affairs Topical Tretinoin Chemoprevention Trial, Cancer, 115:2523-2530.

Jorizzo JL (2005) Current and novel treatment options for actinic keratosis, J Cut Med Surg, 8:13-21.

Lehmann P (2007) Methyl aminolaevulinate-photodynamic therapy: a review of clinical trials in the treatment of actinic keratoses and nonmelanoma skin cancer, BJD, 156:793-801.

Braathen LR, Szeimies RM, Basset-Seguin N, et al (2007) Guidelines on the use of photodynamic therapy for nonmelanoma skin cancer: an international consensus. International Society for Photodynamic Therapy in Dermatology, 2005, JAAD, 56:125-43.

Ulrich C, Jurgensen JS, Degen A, et al (2009) Prevention of non-melanoma skin cancer in organ transplant patients by regular use of a sunscreen: a 24 months, prospective, case-control study, BJD, 161(S3): 78-84.