Objectives: To investigate anti-TIF1-γ antibodies in longitudinally followed patients with myositis and cancer.
Methods: Serum levels of anti-TIF1-γ antibodies at different time-points in relation to myositis and cancer diagnosis were analysed by ELISA in 79 patients from a Swedish cohort with polymyositis (PM) and dermatomyositis (DM) and a Spanish cohort restricted to DM patients. Anti-TIF1-γ positive and negative patients were compared with Fisher's exact test, student t-tests and Wilcoxon test.
Results: Thirty-six patients (17 from cohort 1 and 19 from cohort 2) with myositis and cancer were anti-TIF1-γ antibody positive; all had DM. In 88% of anti-TIF1-γ positive patients, cancer was diagnosed within 3 years from DM diagnosis compared to 63% in anti-TIF1-γ negative. Four DM patients, anti-TIF1-γ positive at cancer diagnosis had positive serum samples even antedating cancer diagnosis up to five years. In cohort 1 the median (interquartile range) antibody level was higher, 2.13 au (1.82-2.15), in the seven patients who died <1 year after cancer diagnosis, compared to the seven that died >1 year after cancer diagnosis, 1.34 au (0.92-1.59), (p=0.004). Three patients were still alive and in remission from cancer and DM 14-16 years after cancer treatment of whom two became negative for anti-TIF1-γ antibodies. In the second cohort remission of cancer coincided with remission of DM and low or negative serum levels of autoantibodies.
Conclusions: Anti-TIF1-γ antibodies may be detected before clinical symptoms of cancer and may disappear after successful treatment of cancer with remission of DM supporting DM being a paramalignant phenomenon.