Question:
Does Sun Exposure Increase Survival from Melanoma?
Answer:
According to the Mayo Clinic, skin cancer is the most common cancer in
the United States. The incidence of skin cancers has been increasing
for the last 50 years in all developed countries. Mortality from skin
cancers has also been increasing, although not as greatly as the
incidence. All forms of skin cancer have been on the rise. More benign
forms include basal cell and squamous cell carcinomas. However, the
greatest rise has been in melanoma, which is the most serious and most
deadly type of skin cancer. The percentage of people with melanoma has
more than doubled over the last 30 years.
Because of the consistent findings that intermittent sun exposure is
associated with an increased risk for melanoma, public health officials
have recommended that excessive sun exposure should be avoided.
Recommendations generally include avoiding sun exposure and use of
sunscreens throughout the year.
A recent study in the Journal of the National Cancer Institute
contradicts this advice. The study looked at 528 melanoma patients who
were entered in the Connecticut Tumor Registry. They examined a number
of factors to determine the risks related to death from melanoma.
They found that sunburn, high intermittent sun exposure, solar
elastosis, which is a marker of sun damage, and self-reported skin
awareness were all linked to improved survival from melanoma. "Sun
exposure was statistically significantly inversely associated with risk
of death from melanoma, regardless of the measure used. Individuals who
has ever been severely burned or who has high levels of intermittent
sun exposure were less likely to die from melanoma than individuals who
had never been severely sunburned or who had low levels of intermittent
sun exposure respectively."
The authors also found that, "recent sunscreen use nor childhood
sunscreen use were statistically associated with the risk of death from
melanoma." They did find that individuals who paid attention to their
skin have a lower risk of death from melanoma, however, "reported
skin self-examination and physician skin examination were not
significantly associated with the risk of death from melanoma."
Attempting to explain their findings the authors note that sun exposure
is essential for the skin to make vitamin D3. Vitamin D has been shown
to be anticancer in nature and therefore could explain the beneficial
association between sun exposure and survival from melanoma. Another
possibility put forward is that sun exposure induces less aggressive
melanoma by increasing the DNA repair capacity and thus reducing
further more deadly changes in melanoma.
The authors conclude that, "we found that intermittent sun exposure
may increase survival from melanoma. If these results are confirmed,
our findings have the potential to lead to interventions, such as
stimulation of the vitamin D pathway or DNA repair capacity, that would
increase survival from melanoma and, perhaps, from other cancers."
