UV radiation is an avoidable cause of skin cancer, the most common malignancy in the United States.1 Emphasize to patients that photoprotection strategies can reduce the incidence of melanoma and nonmelanoma skin cancers and can minimize photoaging. You can also teach patients to perform skin self-examinations and show them how to identify suspicious lesions that warrant medical evaluation.
In this article, we will review effective preventive measures. We will also discuss the evaluation and treatment of common skin cancers.
EFFECTS OF UV RADIATION
The major cause ofnonmelanomaskin cancer is UV radiation, which directly damages cells and alters immunological function.2 UVB is absorbed within the epidermis and upper dermis, where it can cause erythema (sunburn), edema, and hyperpigmentation.3,4 An initial phase of erythema is a prerequisite for the development of UVB-induced hyperpigmentation.3 Long-term UVB exposure results in photoaging, immunosuppression, and photocarcinogenesis.3 UVB exerts its carcinogenic effect in part by causing mutations in oncogenes and tumor suppressor genes.5 For instance, UVB-induced mutations in the p53 tumor suppressor gene inhibit protective cellular responses to UV damage.6
UVA, which has a longer wavelength than UVB, penetrates deeper into the dermis and causes oxidative stress that results in photoaging, immunosuppression, and possibly skin cancer.2 Photoaging results from structural damage to dermal collagen and elastin fibers; the clinical symptoms include dryness, irregular pigmentation, wrinkling, elastosis, telangiectasia, and purpura.
Cumulative sun exposure best correlates with the risk of squamous cell carcinoma (SCC), whereas episodic, and especially intense, sun exposure may better correlate with the risk of basal cell carcinoma (BCC) and melanoma.2,7
Photoprotection and sun-safe strategies are listed in Table 1.
Types of sunscreen. Sunscreens may contain absorbents, reflectants, or a combination of both. Absorbent sunscreens (eg, avobenzone and ecamsule)constitute chemical filters that absorb a component of UV radiation. Reflectant sunscreens, such as titanium dioxide and zinc oxide,contain small particles that reflect or scatter UV radiation. While many sunscreens provide effective UVB protection, few adequate UVA sunscreens are available. The most effective UVA sunscreen ingredient that is available in the United States is ecamsule, which was approved by the FDA in July 2006.8,9
The ability of a sunscreen to prevent burning is indicated by its sun protection factor (SPF), which denotes the relative amount of time a person can tolerate UVB radiation exposure before erythema is induced. For example, a sunscreen with an SPF of 15 protects skin from erythema 15 times longer than would be possible without sunscreen. However, the SPF of a sunscreen relies on adequate and frequent reapplication.
An effective sunscreen regimen. This includes the daily, liberal application of a broad-spectrum sunscreen that contains avobenzone, ecamsule, or a micronized reflectant sunblock. The SPF should be at least 15. During outdoor activities, sunscreen should be reapplied every 2 hours and after swimming, toweling off, or excessive sweating.
Sunscreen and nonmelanoma skin cancer. The regular use of sunscreen prevents actinic keratosis, which can potentially develop into SCC.7,10,11 Use of a sunscreen with an SPF of 15 or higher during the first 18 years of life is hypothesized to decrease the lifetime incidence of BCC and SCC by 78%.12 However, UV damage accrues throughout life, and this hypothesis might diminish patients' motivation to use sunscreen regularly and properly later in life.Because SCC of the lip is particularly aggressive, lip balms with sunscreen are also recommended.13
Sunscreen and melanoma. The association between sunscreen use and melanoma protection is controversial.11,14 Although Hill and Ferrini15 concluded that there is insufficient evidence to recommend sunscreen use, particularly if it leads to increased sun exposure, most experts recommend sunscreen as part of a comprehensive photoprotection regimen.16 Advise patients that over-reliance on sunscreen protection can inadvertently lead to increased intensity and duration of sun exposure.
Self-examination. Training patients to perform self-examinations can increase the frequency of skin surveillance between visits, promote earlier detection of cancers, and result in a more focused and organized office skin examination.17 Self-examination also reinforces many photoprotection principles. Patients can be taught how to perform these examinations during office visits and by means of educational materials available on the Internet as well as in print (Box I).
Self-examination requires the use of a hand mirror or the help of an assistant to check every area of skin for unusual macules, papules, and nodules. Some health care providers and patients overlook the interdigital and genital regions; however, these are important locations for certain types of melanoma.12
Patients can use the "ABCDE" warning signs of melanoma to evaluate any unusual nevus (Table 2).18 As many as 67% of melanomas are detected by patients.19 Mortality associated with melanoma is reportedly lower in patients who perform skin self-examinations.20
Many patients wait until lesions are painful or bleeding before they seek care.21 Persons with darker skin may harbor the dangerous misconception that the additional melanin in their skin fully protects them from skin cancer. Educating patients about the epidemiology, prognosis, signs, and symptoms of skin cancers can allay fears and encourage earlier presentation.22
Office examination. Guidelines vary on the recommended frequency of office skin examinations (Box II). The US Preventive Services Task Force found insufficient evidence to recommend routine screening with a total-body skin examination for the early detection of cutaneous melanoma, BCC, and SCC.23 The organization with the most stringent guidelines, the American Cancer Society, recommends a cancer-related checkup, including a skin examination, during the periodic physical examination for all adults older than 20 years.24 The American Academy of Dermatology recommends at least annual dermatologist-conducted skin examinations, especially for patients at high risk for melanoma.25
A survey showed that the greatest obstacle to performing a skin examination in a primary care setting is lack of time.26 Clinicians were more likely to provide skin examinations for patients who requested them.26
Patients can be examined for signs of skin cancer during routine physical examinations, or they can be referred to dermatologists, free skin cancer screenings, and self-education materials.21 Patients who have risk factors for skin cancer and those who have obvious signs of sun damage need to be examined regularly and counseled about photoprotective strategies.21 Risk factors for melanoma include a history of blistering sunburns in childhood, atypical nevi, and melanoma in a first-degree family member.Encourage all patients to perform regular skin self-examinations.21
Melanomas are 6 times more likely to be detected when all skin is visible during an examination.12 The hands are an easy location to start with and may put your patient at greater ease. Correct lighting and cross-illumination are crucial. Daylight is ideal; however, a combination of incandescent light, which enhances red colors, and fluorescent light, which enhances blue and yellow colors, is acceptable.21 Cross-illumination highlights subtle changes in elevation and reduces glare.21
Palpation of cutaneous lesions may help diagnose skin cancers. Actinic keratosis has a gritty, sandpaper-like surface.21 The pearly quality of a BCC may be better appreciated on blanching.21 Debridement of crusts may be necessary to visualize underlying skin lesions.21