 |
by Michael Caswell, Ph. D. |
Melanoma, Again
The problem started one cold North Carolina morning when I had to wear a long-sleeve shirt. The first soccer game started at 8 a.m.; the second at 10 a.m. As the sun rose high in the sky, the temperature increased as well, eventually topping 90 degrees. Before the second game, I removed the long-sleeve shirt in favor of a short-sleeve shirt. During the third game, I noticed that my arms were itching. After a few feeble attempts at scratching, I looked at my arms. I needed to call a fire department.
My face was fine, but my arms looked like a neon sign. At that moment I realized the power of sunscreens. I had applied a generous amount to my face and scalp, but avoided my arms because they were covered with a long sleeve shirt. My mistake pained me for two weeks.
The Pain Continues
The most recent uproar over the possibility of sunscreens causing melanoma causes me greater pain. This most recent study is not scientifically sound, provides no new evidence to support or refute the relationship between sunscreen use and melanoma, and provides no hypothesis for a relationship. The study is best ignored.
However, we cannot ignore the study because the newspapers and commentators have exploited it to create a controversy. The sunscreen industry has declared that the study is flawed, which it is. Some in the tanning industry have said that the study supports sun exposure, which it does not. The study supports neither side of the tanning controversy.
The Flawed Study
Dr. Marianne Berwick, an epidemiologist from Memorial Sloan-Kettering Cancer Center, based in New York, presented data from a 10-year retrospective melanoma study at the American Association for the Advancement of Science meeting. Her data suggested (not proved) that the use of sunscreen does not protect against melanoma. Previous studies have suggested that the use of sunscreens does not influence the incidence of melanoma. Some scientists have suggested that sunscreens can increase the incidence of melanoma.
The study conducted by Dr. Berwick is a flawed and poorly conducted study. The study was conducted over the past 10 years, but available scientific data indicate that skin cancer develops 15 to 20 years after the insult. (I reviewed this data in the July 1997 issue of LOOKING FIT in an article titled "PUVA1 Therapy Induces Melanoma.") Because of this delay between the insult and the development of skin cancer, even if sunscreens did induce melanoma, Dr. Berwick would have been unable to find the relationship in her study. As Dr. Ceilley, President of the American Academy of Dermatology, noted, "The study asked only about sunscreen use in the prior 10 years, whereas skin cancer typically occurs many decades after the damaging sun exposures." The study was poorly done.
Sunscreen Use and Melanoma--Theory & Fact
In the November 1997 issue of LOOKING FIT, I examined several theories on the cause of melanoma, including the Garland study.
Theory: In 1993, the Garland brothers of San Diego proposed that sunscreens are responsible for the increase in melanoma. They examined large populations and reported that the rise in melanoma correlated with a rise in sunscreen sales.
They offered two possibilities for the correlation in sunscreen sales and increased melanoma. First, they suggested that sunscreen filters the UVB rays, but still allows the UVA rays to penetrate into the skin. Their suggestion indicates that UVA severely damages the skin in ways that have not yet been discovered. Second, they suggested that sunscreen use reduces the amount of UVB reaching the skin that is necessary for vitamin D production. The lack of vitamin D might lead to the increased levels of melanoma.
Fact: Considering published data, skin cancers and melanoma probably take about 15 to 20 years to develop. If the increased sales of sunscreen were responsible for the increase in melanoma, we would expect to see a delay of about 15 years between the increase in sunscreen sales and the increase in melanoma. This is not the case. Dr. Fred Urbach stated during the 1995 Biological Effects of Light Symposium that the incidence of melanoma has been doubling consistently every 10 years since the 1930s according to the Connecticut Registry. This would indicate that whatever is causing the increase in melanoma first began around 1915 or earlier. Sunscreen use began in the 1940s. Clearly, sunscreens had no effect on melanoma development in the 1930s.
Vitamin D deficiency has not been associated with increased incidence of melanoma. In the 19th century, children in inner cities of England suffering from rickets were not reported to have had an increased incidence of melanoma. Rickets results from a severe deficiency in vitamin D. To my knowledge, there has never been any study correlating an increase in melanoma with vitamin D concentration.
An Important Review by Drs. Swerdlow & Weinstock
Much important scientific work usually is unnoticed by newspapers and magazines if the work does not create a dramatic headline. Thus, Dr. Berwick's study receives worldwide newspaper and magazine coverage while a much more important article by Drs. Swerdlow and Weinstock is essentially ignored.
Their article, titled "Do Tanning Lamps Cause Melanoma? An Epidemiological Assessment," was published in the January 1998 edition of the Journal of the American Academy of Dermatology. The article is the finest review to date on the relationship between UV exposure and melanoma.
The authors reviewed 19 studies on the association of tanning beds or other UV lamps with melanoma. While most studies found no statistically significant association, six found a significant positive association (i.e., that use of tanning lamps increases the incidence of melanoma) and none found a significant inverse correlation (i.e., that use of tanning lamps decreases the incidence of melanoma). As the authors noted, six flaws in these 19 studies limit the value of the studies and prevent any solid conclusions from being drawn.
- None of the studies were able to obtain information on the amount of ultraviolet radiation exposure from the tanning beds.
- Each of the studies depended on recall of the study subjects.
- Many of the studies compared those who had used a tanning bed (even if only once) to those who had never used a tanning bed.
- Analysis of the data in most studies was poorly documented.
- Outdoor exposure was not controlled in most studies.
- Most studies did not examine enough tanning bed users to create reliable statistics.
Drs. Swerdlow and Weinstock conclude that " ... the published data is insufficient to determine whether tanning lamps cause melanoma." The authors call for better research in the area to overcome many of the six problems listed above. Dr. Berwick's study does not meet this call.
My Healthy Skin Perspective
There are many theories and very few facts on the causes of melanoma. From Dr. Stern's research, we can conclude that PUVA can induce melanoma after 15 to 20 years of treatment. We know little else about the cause of melanoma for certain. My perspective is that a combination of agents causes melanoma. I believe that the agents responsible for melanoma have been with us for at least 70 years and in increasing amounts.
Tanning and sunscreens are an important combination for healthy skin. My perspective is that controlled UV exposure adds to the health of skin by providing vitamin D and protective melanin and the best way to obtain a controlled exposure to ultraviolet radiation is in a quality tanning bed. Sunscreens are necessary when you suspect that you might be in the outdoor sun for a long time. Sunscreens prevent burning and peeling and protect the tan you have worked to achieve. Moderate tanning sunscreens used outdoors are a powerful combination to prevent overexposure to the UV rays of the sun.
