Correcting results for guarantee-time bias weakened the association, according to a paper in JNCI.

The appearance of autoantibodies is not strongly associated with improved outcome in melanoma patients treated with interferon, scientists report, contradicting what was previously believed. They note that once association results were corrected for the time it takes patients with better outcomes to become antibody-positive, the previously noted link between autoantibdoies and the disease became weak.

“The findings indicate that the assessment of autoimmune antibodies is not a useful tool in selecting patients who would benefit from treatment with intermediate doses of IFN-a2ß,” the authors write in their paper titled, “Autoimmune Antibodies and Recurrence-Free Interval in Melanoma Patients Treated With Adjuvant Interferon.” It is published in the June 9 issue of the Journal of the National Cancer Institute.

Serum levels of anticardiolipin, antithyroglobulin, and antinuclear antibodies were determined using enzyme-linked immunosorbent assays in 543 patients from two controlled, randomized trials. Measurements were taken immediately before and up to three years after random assignment. The association of the presence of at least one of the three autoantibodies with risk of recurrence was assessed in patients negative for all three autoantibodies at baseline using three Cox models: a model that considered appearance of autoantibodies as a time-independent variable, one that considered a patient autoantibody-positive once a positive test for an autoantibody was obtained, and a model in which the status of the patient was defined by the most recent autoantibody test.

When treated as a time-independent variable, appearance of autoantibodies was associated with an improved relapse-free interval in both trials. The researchers then corrected for guarantee-time bias, which is the additional time that patients with improved outcomes have to become antibody-positive. Accounting for this time, the scientists found that the association was weak and not statistically significant.

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