SAN DIEGO — Data on the estimated incidence of melanoma in the United States in 2010 from the National Cancer Institute's Surveillance, Epidemiology and End Results program will not be available until later this year, but Dr. Darrell S. Rigel does not expect the news to be good.
"Melanoma rates are rising significantly in the United States and in other parts of the world," he said at a melanoma update sponsored by the Scripps Clinic.
"Whatever criteria you use, it's clear that we're seeing more melanomas than we've seen in the past, and we'll probably continue to do so in the next 5-10 years."
According to the most recent SEER data, in 2009 there were 68,720 newly diagnosed cases of invasive melanoma and 53,120 cases of in situ melanoma. Dr. Rigel and his associates at the New York University Interdisciplinary Melanoma Cooperative Group estimate that the projected lifetime risk of invasive melanoma was 1:58 in 2009, up from 1:65 in 2004.
"Should that rate of increase continue, the risk will be about 1:50 by the year 2015," said Dr. Rigel, who is a professor of dermatology and dermatologic surgery at New York University Medical Center. "We've been pretty close on these projections over the last few years. One in 50 is a lot. That's 2% of the population."
Factor in the incidence of in situ melanoma, and the risk of any American getting any kind of melanoma jumps to 1:30, which would be 121,840 total cases in 2009.
"It's a significant problem," he said.
Nine years ago, researchers who analyzed the melanoma incidence rates in the United States from 1960-1997 forecasted a subsequent growing incidence of melanoma. They concluded that the increase in melanoma incidence is real - "not due to improved diagnosis," Dr. Rigel said - and predicted that the incidence would continue to rise for the next decade or more (J. Natl. Cancer Inst. 2001;93:67-83).
Results from studies published in the past decade suggest that the incidence of melanoma is also rising in other parts of the world. In Finland, for example, the incidence of melanoma increased from 1.5 cases to 12.8 cases per 100,000 men between 1953 and 2003, and from 1.8 cases to 10.4 cases per 100,000 women during the same time period (Int. J. Cancer 2006;119:380-4).
In central Greece, the incidence increased from 1.4 cases to 5.2 cases per 100,000 people between 1988 and 1998 (Int. J. Tissue React. 2005;27:173-9). Melanomas were most frequently located on the head and neck, extremities, and trunk.
In Columbia, the incidence of melanoma increased from 2.7 cases to 13 cases per 100,000 people between 2003 and 2005 (Rev. Salud Pública 2007;9:595-601).
Dr. Rigel emphasized that results from the best available studies in the medical literature suggest that the rising incidence of melanoma cannot be explained by increased surveillance, awareness, or by changing histologic criteria. However, while the number of melanoma deaths continues to rise, 5-year survival rates are improving - from 86% between 1985 and 1989 to 92% between 1995 and 2002 (Cancer J. Clin. 2007;57:43-66).
"That seems incongruous," Dr. Rigel said. "The only way that can be happening mathematically is that the incidence has to be rising even faster. That's a compelling reason to explain why the rising incidence is real. According to the World Health Organization, melanoma is rising faster than any other cancer worldwide, on a percentage basis."
He went on to note that the current incidence of melanoma is probably underreported because data from SEER are collected primarily from hospitals.
"The biopsy may be done in an outpatient setting," he explained. "It may go to an outpatient lab; it may be re-excised, and then it may go back to the same lab. It may never hit a hospital. That's why melanoma probably is significantly undercounted."
According to the American Cancer Society, melanoma kills one American citizen per hour. "Some people pooh-pooh skin cancer," Dr. Rigel said. "It's the most common cancer in women aged 25-29, and it's the number one cancer killer in women aged 30-35. There are some subsets of the population that are particularly hurt by this disease."
Dr. Rigel disclosed that he receives grants and advising and consulting fees from a number of pharmaceutical companies, including Neutrogena, Johnson & Johnson, Procter & Gamble, and Beiersdorf.