Melanoma is a skin cancer that originates in pigment-producing cells called melanocytes. Metastatic melanoma refers to disease that has spread to other parts of the body that are regional or distant from the site of origin. Malignant melanoma is becoming a more prevalent cancer. It has been suggested that no other cancer is increasing faster in terms of number of new cases diagnosed. In 1995, approximately 32,100 patients in the United States developed malignant melanoma, of which 7,200 died. According to the World Health Organization over 60,000 new cases of invasive melanoma will be diagnosed in the United States in 2008. Moreover, according to the American Cancer Society (Cancer Facts & Figures 2008), over 8,000 people will die from melanoma in the United States in 2008, approximately one person every hour. The death rate for melanoma has doubled in the last 35 years, with increases of approximately 5% per year in the older Caucasian population. The National Cancer Institute reports that melanoma has become the most common form of cancer in young adults.
The reasons for this epidemic are not entirely clear. However, an increased amount of ultraviolet B radiation from sunlight reaching the earth, an increased recreational exposure to sunlight, and an earlier detection of melanoma all have been cited as contributing factors to this epidemic. In 1935, melanoma developed in only one in 1,500 individuals. By 1980, this ratio had increased to one in 250, and by the year 2000 it had increased dramatically to one in 75.
Prognosis for melanoma depends primarily on the stage of the lesion. Patients with clinically localized melanoma (stages I and II) have a 10-year survival ranging from approximately 65% to 90%.
Once patients develop metastatic melanoma to regional lymph nodes (Stage III), they have a 10-year survival of ~40%, while those with two or more metastatic nodes have ~15% survival; the overall 10-year survival is ~25%.
The prognosis for patients with metastatic melanoma at distant sites (stage IV) is even grimmer. The one-year survival for patients with distant metastases to the skin and internal organs is 10% to 25%.
Patients with metastatic melanoma at distant sites (stage IV) respond poorly to most therapies. Indeed, although responses have been observed, none of the therapies have demonstrated an improvement in overall survival, including chemotherapy, biological therapy, radiation therapy and vaccine therapy.