Survivors of melanoma skin cancer are nine times more likely to develop another melanoma than the rest of the population, and are at a much higher risk of being diagnosed again with any kind of cancer, according to new research.
The findings suggest that melanoma survivors need lifelong cancer monitoring.
Melanoma is not the most common form of skin cancer, but it is the most serious. In 2009, an estimated 5,000 Canadians were diagnosed with the cancer and 940 Canadians died.
While the incidence for the majority of cancers in Canada are stabilizing or even declining, melanoma rates are still increasing.
Melanoma's survival rate is high, with 87 per cent of diagnosed men and 93 per cent of women still alive after five years. But the risk for a second diagnosis of melanoma is also high, this research confirms.
To quantify the risk, Dr. Portia T. Bradford and colleagues at the National Cancer Institute in the U.S. looked at nine cancer registries of the Surveillance, Epidemiology, and End Results (SEER) program. It tracked nearly 90,000 patients who survived at least two months after a first melanoma diagnosis, between 1973 and 2006.
About 12 per cent of melanoma survivors went on to develop one or more other primary cancers, the authors report in the Archives of Dermatology.
Of those, one-fourth were additional melanomas. Women with head and neck melanoma, and patients younger than 30, had even higher increased risks of developing another melanoma.
As well, doctors diagnosed 1,156 female breast cancers, 2,200 prostate cancers and 481 non-Hodgkin's lymphomas.
In each case, the number of secondary cancers reported among survivors was higher than what would have been expected in the general population.
The researchers conclude that melanoma survivors have a 28 per cent increased risk of a second cancer, and a nine times greater likelihood of developing another melanoma than the general population.
The risks of a second cancer were highest within the first year; they declined somewhat over time but "remained quite elevated more than 20 years" after the first diagnosis.
"This increased risk may be owing to behavioral factors, genetic susceptibility or medical surveillance," the authors conclude.
They add that melanoma survivors need lifelong medical surveillance not only for new melanomas but for other cancers as well.
In a second study in the same issue of the Archives of Dermatology, researchers led by U.S. dermatologist Dr. Howard Rogers, found that incidence of non-melanoma skin cancer has steadily increased since the 1990s.
The cancers are now, by far, the most common form of cancer -- affecting more people than all other cancers combined -- with the incidence still rising.
The researchers report that from 1992 to 2006, cases of non-melanoma skin cancer in the U.S. population covered by Medicare rose an average of 4.2 per cent a year, according to the study.
"These data give the most complete evaluation to date of the under recognized epidemic of skin cancer in the United States," the authors say.
The researchers called non-melanoma skin cancer an "epidemic" that is only going to get worse.
"We are dealing with a problem that is not going away," said Rogers.
In an accompanying editorial, researchers from Erasmus University Medical Center in Rotterdam, the Netherlands, called for a "revised health strategy" that treats skin cancer as a chronic disease requiring not just a one-time treatment, but ongoing monitoring of patients, prevention and education.
"Skin cancer needs to be regarded as a chronic disease and should not be considered a solitary event requiring the treatment of one tumor," they write.
It is not clear why some people develop melanoma and others do not, but there are some known risk factors. They include:
- Large moles called dysplastic nevi. The risk of melanoma is greatest for people who have a large number of dysplastic nevi
- Many (more than 50) ordinary moles
- Fair skin that burns or freckles easily (these people also usually have red or blond hair and blue eyes)
- Family history of melanoma. Having two or more close relatives who have had this disease is a risk factor
- People with immune systems weakened by cancer, by drugs given following organ transplantation, or by HIV
- Severe, blistering sunburns. People who have had at least one severe, blistering sunburn as a child or teenager are at increased risk of melanoma
- Ultraviolet (UV) radiation. Experts believe that much of the worldwide increase in melanoma is related to an increase in the amount of time people spend in the sun. UV radiation from the sun causes skin damage that can lead to melanoma. Artificial sources of UV radiation, such as sunlamps and tanning booths, also can cause skin damage and increase the risk of melanoma
