NEW YORK (Reuters Health) - Patients with rheumatoid arthritis who are treated with methotrexate appear to have an elevated risk of developing melanoma compared with the general population, according to the findings of an Australian study.
Dr. Rachelle Buchbinder, at Monash University, and colleagues studied 458 patients with rheumatoid arthritis who started methotrexate therapy at six private rheumatology practices in Melbourne, Victoria, before June 1986. The medical records showed that 64 malignancies were diagnosed during the follow-up period, which averaged 9.3 years, and an additional 9 cases were diagnosed after the patients had exited follow-up.
Malignancy rates in the general population were determined from the Victorian State Cancer Registry and the National Death Index. The complete findings are reported in the June 15 issue of Arthritis & Rheumatism.
Melanoma, the most serious type of skin cancer, also has a greater tendency to spread and is associated with higher mortality rates compared with other types of skin cancer. According to U.S. government statistics reported between 2001 and 2005, the average age at diagnosis was 59 years. Less than 1 percent of cases were diagnosed in patients under 20 years old. The highest rates, at 19.5 percent, were among individuals between 45 and 54 years. Adjusting the data for age, the mortality rate was 2.7 per 100,000 men and women per year. The average age at death was 68 years old.
Methotrexate is considered a second-line therapy for rheumatoid arthritis; it is used when the first-line drugs are not effective. The mechanism of action for this drug in rheumatoid arthritis is not completely understood. It appears to work, at least in part, by altering immunity, which may play a role in rheumatoid arthritis.
The investigators estimated that there was a 50 percent increase in the risk of this malignancy among the rheumatoid arthritis patients compared with the general population. Methotrexate-treated patients also had five-times the risk of non-Hodgkin's lymphoma, three-times the risk of lung cancer and three times the risk of melanoma.
