Summary: Sunlight Exposure, Pigmentation Factors, and Risk of Nonmelanocytic Skin Cancer I. Basal Cell Carcinoma 

Basal cell carcinoma (BCC) of the skin is the most common malignancy among white populations in Europe, North America and Australia. Sunlight exposure is generally considered the most important environmental risk factor for developing this tumour.

This study (sunlight_i.pdf) evaluated the relationship between sunlight exposure, pigmentary factors and basal cell carcinoma, because little information is available on the character and timing of sunlight exposure responsible for BCC. The results showed:

• Significantly elevated risks for BCC among subjects with:
  • Light skin colour.
  • Red hair.
  • A tendency to burn, not tan, after sun exposure.
• Subjects whose mothers were of Southern European ethnic origin were at significantly lower risk for BCC than those whose mothers were of English, Celtic and Scandinavian origin.
• Freckling in childhood increased the risk for developing BCC later in life.
• Only recreational childhood exposure showed a significant link to risk of BCC. Subjects who had frequent or severe sunburns in childhood and adolescence, up to 19 years of age, had increased risk compared to those who did not recall being sunburned. This increased risk was evident only among non-tanners. (Subjects were divided into tanners, people who get a brown suntan without burning, and non-tanners, who usually sunburn followed by a tan, or only burn.)
• Sunburn history as an adult, from age 20 on, did not show any risk for BCC.
• Cumulative sun exposure, combining recreational and occupational exposure, did not show an association with BCC.
• There was no association between degree of tanning and risk of BCC.

The results of this study suggest that childhood sunlight exposure may be an important factor in adult risk for BCC. The increased risk seen among people with light skin correlates with results from several previous studies, as does the protective nature of Southern European ancestry. Light hair colour has also been shown to increase risk in several investigations, with red-haired individuals at highest risk.

In addition, the association between freckling and BCC is important, because the findings correlate with another study, and freckling is a well-established risk factor for melanoma and may be a marker for UV light damage to the skin.

The fact that sunburn in childhood, particularly severe sunburn, substantially increased risk for adult BCC, while no such effect was seen for adult sunburn, suggests skin may be more sensitive in childhood to initiating events that eventually lead to malignancy. Again, a similar relationship has been detected for malignant melanoma.

While the findings from this study require confirmation, they indicate:

• The timing and character of sun exposure may be more important than cumulative dose in predicting adult risk for basal cell carcinoma.
• Among sensitive individuals, sun avoidance behaviour in adulthood may not markedly reduce risk for this tumour.

You can refer to the complete journal article for additional details on the:

• Study design, methods and materials.
• Data collected during the study.
• Comments on interpreting the data.