The increased risk of cancer associated with anti-TIF1-Ab-positive dermatomyositis is limited almost exclusively to 3 years on either side of the onset of dermatomyositis, new research suggests.
Idiopathic inflammatory myopathy have been associated with malignancy, in particular dermatomyositis (DM) and the DM-specific antitranscriptional intermediary factor 1 antibody (anti-TIF1-Ab).
Around one-fifth of the 236 patients diagnosed with DM in the current study, published online Dec. 7 in Rheumatology, were anti-TIF1-Ab positive, and these patients had a more than threefold higher risk of developing cancer comapared with patients who were anti-TIF1-Ab negative (hazard ratio = 3.4, 95% confidence interval, 2.2-5.4; P less than .01).
Overall, 38% of patients in the anti-TIF1-Ab-positive group developed cancer during the 10-year follow-up, compared with 15% of patients with anti-TIF1-Ab-negative DM.
However, all the cancers in the anti-TIF1-Ab-positive group occurred within the 3 years before the onset of DM or within 2.5 years after onset. No anti-TIF1-Ab-positive patients developed cancers after this time, but some patients in the anti-TIF1-Ab-negative group did.
“This finding is not likely to be due to a disparity in follow-up time between anti-TIF1-Ab-positive and -negative cases, as the median follow-up times were similar for both groups: 10 years and 12 years, respectively,” wrote Alexander Oldroyd, MBChB, a clinical research fellow in the Centre for Musculoskeletal Research at the University of Manchester (England), and his coauthors. “Further, this finding is unlikely to be due to differences in cancer detection methods, as both cohorts’ cancer diagnoses were identified through HSCIC [U.K. Health and Social Care Information Centre] data, ensuring capture of all incident cancers during the follow-up period.”
Anti-TIF1-Ab-positive patients were more likely to develop cancer if they were older. None of the 15 anti-TIF1-Ab-positive patients who were aged under 39 when they developed DM went on to develop cancer. But cancer developed in around half of the anti-TIF1-Ab-positive patients who were aged 39 years or older when their DM began.
The anti-TIF1 antibody is commonly found in juvenile DM, but previous research has not found an association with an increased risk of cancer in this younger patient population.
“Our findings add strength to the hypothesis that there exists a subset of young adult anti-TIF1-Ab-positive cases who do not have a discernible increased risk of cancer, similar to that observed in TIF1-Ab-positive juvenile DM,” the authors wrote. They suggested that given the increased risk of malignancy in older patients who were anti-TIF1-Ab positive, this group should be subject to more detailed cancer screening.
Breast cancer was the most common malignancy among both anti-TIF1-Ab-positive and anti-TIF1-Ab-negative patients (33% and 25%, respectively). However, ovarian cancer was significantly more common among the anti-TIF1-Ab-positive patients than among the anti-TIF1-Ab-negative patients (19% vs. 2%; P less than .05); four of the five ovarian cancers in the entire cohort occurred in the anti-TIF1-Ab-positive group.
The authors noted that this confirmed the finding of a number of previous studies suggesting an increased risk of ovarian cancer with DM.
“However, this is the first large study to identify that ovarian cancer is overrepresented in anti-TIF1-Ab-positive individuals, suggesting that the true association between DM and ovarian cancer may be through possession of anti-TIF1-Abs,” they noted.
The authors wrote that they had aimed to inform cancer screening strategies among patients with DM.
“It may be that a focus on screening for cancer within the first 3 years after DM onset and particularly screening for ovarian cancer in anti-TIF1-Ab-positive female patients may be required,” they wrote. “Our findings also strengthen the hypothesis that inflammatory myopathies represent a paraneoplastic reaction initiated by attempted immune-mediated clearance of a cancer.”
The study was supported by Arthritis Research UK, Myositis UK, the European Science Foundation for EuMyoNet, Association Francaise Contre Les Myopathies, the Medical Research Council, and the Manchester Academic Health Science Centre. No conflicts of interest were declared.
SOURCE: Oldroyd A et al. Rheumatology. 2018 Dec 7. doi: 10.1093/rheumatology/key357.