The findings show that people who have had melanoma require lifelong follow-up, the study authors said.
The investigators looked at over 4,700 melanoma patients and found that recurrence occurred in 408 patients who had been disease-free for 10 or more years. The recurrence rates were nearly 7 percent after 15 years and 11 percent after 25 years, according to the study in the July issue of the Journal of the American College of Surgeons.
But the researchers also found that patients whose melanoma recurred 10 or more years later were less likely to die than those whose melanoma recurred within three years of treatment. Those with late recurrence were about 40 percent less likely to die of melanoma than those with early recurrence, and those with late recurrence also had a better overall survival rate.
Patients whose melanoma did not come back until at least 10 years after treatment were younger on average than those with early recurrence (age 41 versus 51).
Also, patients with a later recurrence tended to have had an original melanoma with less dangerous characteristics, the researchers noted. They also found that men accounted for 66 percent of patients with early recurrence, compared with 57 percent of those with late recurrence.
"For patients with melanoma, survival beyond 10 years without a recurrence has been considered nearly synonymous with a cure," lead investigator Dr. Mark Faries, a professor of surgery at the John Wayne Cancer Institute at Saint John's Health Center in Santa Monica, Calif., said in a journal news release. "However, most studies do not follow-up patients longer than 10 years. Our study found that late melanoma recurrence is not rare and that it occurs more frequently in certain patient groups," he noted.
"It appears the risk of melanoma recurrence is never completely gone," Faries said. "One change that should result from our study is that people need to be followed-up for life with a physician after a diagnosis of melanoma," he pointed out.
"Fortunately, the vast majority of melanoma patients who remain disease-free longer than 10 years will not have a recurrence," Faries added. "However, patients should be aware that persistent or unexplained symptoms anywhere in the body might indicate a recurrence of their melanoma, and they should return to their physician to make sure the symptoms are not related."
Nearly 76,700 new cases of melanoma will be diagnosed in the United States this year, according to the American Cancer Society.
The American Cancer Society has more about melanoma.