Dr. Anna Pudinak on Skin Cancers Related to Excess Sun Exposure: Sponsored Content
 
Dr. Anna Pudinak on Skin Cancers Related to Excess Sun Exposure: Sponsored Conte
 

Each year there are more new cases of skin cancer than the combined incidence of cancers of the breast, prostate, lung and colon. One in five Americans will develop skin cancer in the course of a lifetime. Radiation from the sun is the primary cause of both melanomatous and non-melanomatous skin cancer. Ultraviolet radiation causes genetic mutations and interferes with the cutaneous immune system, limiting the body’s ability to reject abnormal cells. Risk of squamous cell and basal cell cancer appears to correlate with total lifetime sun exposure. Cumulative sun exposure may also increase melanoma risk, but repeated intense exposures leading to blistering burns may be even more dangerous.

Recommendations for Sun Protection

Targeted interventions for high-risk characteristics such as fair skin, large number of nevi, or positive family history, fails to identify an adequate proportion of people who develop disease. All individuals should limit the time spent in the sun, especially between the hours of 10:00 am and 3:00 pm, wear hats, sunglasses, and other protective clothing, and use sunscreen. Because the majority of lifetime sun exposure usually occurs during childhood and adolescence, protective behaviors early in life will provide the greatest benefit. In addition, the World Health Organization has recommended against tanning bed use by anyone under the age of 18.

Epidemiology and Clinical Features of Basal Cell Carcinoma

Basal cell carcinoma is the most common skin cancer arising from the basal layer of epidermis and its appendages. This tumor has been referred to as “epithelioma” because of its low metastatic potential. However, the term carcinoma is appropriate, since it is locally invasive, aggressive, and destructive of skin and the surrounding structures including bone.

Individuals with a history of BCC are at increased risk for subsequent lesions. Approximately 40 percent of patients who have had a BCC will develop another lesion with five years.

BCC is particularly common in Caucasians; it is very uncommon in Afro-Americans and other dark-skinned populations. In white populations in the United States, the incidence of BCC has increased by more than 10 percent per year, and the lifetime risk of developing a BCC is 30 percent. More than 4 million cases are diagnosed the United States each year. The incidence in men is 30 percent higher than in women, particularly with the superficial type. The incidence of BCC increases with age; persons aged 55 to 75 have about a 100-fold higher incidence of BCC than those younger than 20.

Sun Exposure

Sun exposure is the most important environmental cause of BCC, and most risk factors relate directly to a person's sun exposure habits or susceptibility to solar radiation. These risk factors include having fair skin, light-colored eyes, red hair, northern European ancestry, older age, childhood freckling, and an increased number of past sunburns. Childhood sun exposure appears to be more important than exposure during adult life.

The frequency and intensity of sun exposure may also be important. Solar exposure in intermittent, intense increments increases the risk of BCC more than a similar dose delivered more continuously over the same period of time.

It has been estimated that aggressive sun protection before the age of 18 years could reduce the number of non-melanoma skin cancer by almost 80 percent. About 70 percent of BCCs are present on the face and head.

Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma is a common cancer arising from malignant proliferation of epidermal keratinocytes. Cutaneous squamous cell carcinoma is the second most common type of skin cancer in the United States, behind basal cell carcinoma, and accounts for approximately 20 percent of non-melanoma skin cancers. More than 1 million cases are diagnosed in the United States each year.

Risk Factors

Both environmental and genetic factors contribute to the development of cutaneous squamous cell carcinoma. Among light-skinned individuals, the most important risk factors are principally UVB radiation, cumulative sun exposure, and age.

UVB Radiation

In contrast, intense intermittent sun exposure (eg, sunburn, childhood exposure) is the most important risk factor for BCC and melanoma.

Other factors associated with an increased risk of cutaneous SCC and consistent with a causative role for UVB radiation include:

  • The degree of sun exposure in the past 5 to 10 years
  • Occupational sun exposure
  • Phenotypic characteristics such as fair skin, light-colored eyes, red hair, and Northern European origin
  • Actinic keratosis are cutaneous precancerous lesions that are associated with sun exposure,and occasionally progress to SCC. It affects more than 58 million Americans.

Melanoma

Melanoma has become a worldwide public health concern. American Cancer Society’s estimates for melanoma in the United States for 2016: About 76,380 new melanomas will be diagnosed (about 46,870 in men and 29,510 in women). About 10,130 people are expected to die of melanoma (about 6,750 men and 3,380 women). At least two-thirds of melanoma in light-skinned populations worldwide may be attributed to ultraviolet radiation exposure from both natural and artificial sources. Based upon this and other data implicating UV light as a risk factor for melanoma, reducing exposure to UV radiation has been advocated as a method to reduce the incidence of this malignancy.

Although a causal relationship between ultraviolet radiation and melanoma has not been directly demonstrated in humans, there is evidence in support of this relationship:

  •  In the United States, the incidence of melanoma is at least 20 times greater in whites than African-Americans.
  •  Before age 50, melanoma incidence rates are higher in women than in men, but by the age 60, rates are twice as high in men.

Prevention Protection from the sun, including the application of sunscreen and the use of protective clothing, reduces the risk of cutaneous squamous cell carcinoma and its precursor lesion, actinic keratosis. Even relatively short-term use of sunscreen can be beneficial. Exposure in childhood seems particularly important; a history of five or more severe sunburns in adolescence more than doubles the risk of developing melanoma Individuals at increased risk of melanoma and individuals highly exposed to sunlight should apply a broad spectrum sunscreen with an SPF of 15 or higher daily and thoroughly before going out. Because of inconsistent application, the American Academy of Dermatology recommends the use of sunscreen with and SPF of at least 30 during sun exposure.

Clothing

Tightly woven fabrics and dark colors confer the highest UV protection. In addition, photoprotective clothes with designed ultraviolet protection factor ranging from 15 to 50 are commercially available.

Common window glass proves a variable degree of ultraviolet B protection.

Cosmetics and moisturizers for daily use that contain broad spectrum sunscreens may improve the compliance to photoprotection.

Sunscreen use has been shown to modestly attenuate the development of new moles in young children. The use of sunscreen was especially beneficial for freckled children.

General guidelines:

  •  Do not burn; avoid sun tanning