Is melanoma, the most deadly form of skin cancer, unrelated to sun exposure, and does ultraviolet (UV) light primarily cause basal cell carcinoma?

From the Guidelines

No, there is no good evidence that melanoma has little to do with sun exposure. In fact, ultraviolet (UV) radiation from the sun or tanning beds is a major risk factor for all types of skin cancer, including melanoma. While it's true that UV exposure strongly correlates with basal cell and squamous cell carcinomas, substantial evidence also links UV radiation to melanoma development, as seen in studies such as 1, which states that approximately 65%–90% of melanomas are caused by UV exposure.

Key Points

• Studies show that severe sunburns, especially during childhood or adolescence, significantly increase melanoma risk, as noted in 1 and 1.
• Melanoma occurs more frequently on sun-exposed areas of the body, and people with fair skin who burn easily have higher melanoma rates, as mentioned in 1 and 1.
• Other risk factors for melanoma include family history, multiple atypical moles, and certain genetic conditions.
• Sun protection measures including sunscreen use, protective clothing, seeking shade, and avoiding tanning beds are essential preventive strategies against all forms of skin cancer, including deadly melanoma, as recommended in 1, 1, and 1.

Recommendations

• Avoid direct sunlight by staying indoors or in the shade, especially during peak sun hours, to reduce exposure to ultraviolet light, as advised in 1.
• Use broad-spectrum sunscreen with a sun-protection factor of 15 or greater, and wear protective clothing such as broad-brimmed hats, long-sleeved shirts, and long pants, as suggested in 1 and 1.
• Avoid tanning beds, which are a known risk factor for skin cancer, including melanoma, as stated in 1 and 1.

From the Research

Skin Cancer and UV Exposure

• The relationship between skin cancer and UV exposure is complex, with different types of skin cancer having different associations with UV radiation 2.
• Basal cell carcinoma (BCC) is the most common type of skin cancer, and its incidence is increasing, with UV radiation being the most important risk factor in its development 3.
• UVB radiation is believed to play a greater role in BCC formation than UVA radiation, and a latency period of 20-50 years is typical between the time of UV damage and the clinical onset of BCC 3.

UV Exposure and Basal Cell Carcinoma

• Studies have consistently shown that cumulative solar ultraviolet radiation exposure is associated with an increased risk of basal cell carcinoma 4.
• The risk of BCC rises with increasing cumulative ultraviolet radiation exposure, with a greater increase in risk at higher levels of ultraviolet radiation exposure 4.
• High-sun protection factor sunscreen use before age 25 may be associated with lower BCC risk, but use since age 25 and reapplication of sunscreen may be associated with higher risks of BCC 2.

UV Exposure and Melanoma

• Melanoma, the skin cancer causing most deaths, has a different association with UV exposure than BCC, with a history of severe sunburns <25 years being associated with increased risks of melanoma 2.
• However, the relationship between UV exposure and melanoma is complex, and more research is needed to fully understand this association 2.

Prevention and Protection

• Primary interventions for prevention of skin cancer include counseling on reducing sun exposure, use of UV-protective clothing and sunscreen, and discouragement of tanning bed use 5.
• The American Academy of Dermatology recommends skin examinations for all patients with a history of skin cancer at least annually 5.