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Validity of commercial serologic tests for dermatomyositis still questionable



Clinical assessment for pulmonary disease and malignancy in patients with dermatomyositis should not be replaced with serologic tests at this time, according to Jeffrey P. Callen, MD.

Dr. Jeffrey P. Callen, professor of medicine and chief of the division of dermatology at the University of Louisville School of Medicine

Dr. Jeffrey P. Callen

That’s because the validity and reproducibility of testing in commercial laboratories remain questionable, Dr. Callen, professor of medicine and chief of the division of dermatology at the University of Louisville, Ky., said during MedscapeLive’s annual Las Vegas Dermatology Seminar. “The testing in research laboratories is not widely available and the results are often delayed by weeks to months,” he said.

In addition, while the associations between antibody results and risks of malignancy or pulmonary disease are “statistically valid,” he said, “there are patients with disease in whom antibodies are not present and those without associated disease in whom the testing was positive.” For example, there are patients positive for anti–transition initiation factor (TIF)-1gamma but don’t have a malignancy, “and the ones with anti-MDA-5 tend to have pulmonary disease, but there are patients with anti-MDA-5 who don’t have pulmonary disease.”

Compared with patients with systemic lupus erythematosus, patients with dermatomyositis tend to have more itching and they tend of have fewer serologic abnormalities, such as anti-Ro/SS-A antibody, “but there is overlap,” Dr. Callen said. “The reason to differentiate cutaneous lupus erythematosus from dermatomyositis is because we think that patients who have amyopathic dermatomyositis still have an increased risk of having or developing an internal malignancy,” he added. Another differentiating point that is substantive is the presence of Gottron papules.

In a recent development related to antibody testing, researchers demonstrated that the IgG2 isotype of anti-TIF-1gamma antibodies is a biomarker of cancer and mortality in adult dermatomyositis.

According to population-based studies, about 20%-25% of dermatomyositis patients have had, have, or will develop a cancer (Lancet 2001;357: 96-100). Amyopathic dermatomyositis patients may also have cancer. Polymyositis patients generally have lower rates and their risk of subsequent malignancy is much closer to that of the general population, suggesting that the presence of the association is due to a “diagnostic suspicion bias,” Dr. Callen said.

A large-scale multicenter cohort study that set out to identify the risk factors and prognosis of patients with cancer-associated myositis found that ovarian cancer seems to be overrepresented. The only serologic abnormality that was statistically significant was anti-TIF-1gamma antibody (P less than .001). Patients with cancer-associated myositis also have less overall survival compared with those with non–cancer-associated myositis (P = .004), with malignancy being the primary cause of death (P less than .001).

In what is believed to be the largest study of its kind, Dr. Callen and colleagues retrospectively examined the prevalence of malignancy and screening practices in 400 dermatomyositis patients. Of the 400 patients, 48 (12%) had malignancies, and 21 cancers (40%) were diagnosed within 1 year of the dermatomyositis diagnosis. Both classic dermatomyositis and amyopathic dermatomyositis were associated with cancer, and 27 patients (6.8%) had a cancer at the time of diagnosis. Of those, 59% were asymptomatic; their cancers were discovered with CT scans, suggesting that “blind” screening is effective in identifying cancers in DM patients.

Dr. Callen’s malignancy evaluation includes chest x-ray, CT of the chest and abdomen, stool Hematest in all dermatomyositis patients; a mammogram, pelvic ultrasound and/or CT of the pelvis in women; and age, race or ethnicity-related testing. “I generally reevaluate patients annually for 3 years, because data from epidemiologic studies suggest that after 3 years [from the initial diagnosis], the rates of malignancy return toward normal,” he said. “I also evaluate any new symptom that might be suggestive of malignancy. The remaining issue is how to handle a patient in remission for several years, but who develops a relapse. What I do is perform another malignancy assessment.”

According to results from a meta-analysis of risk factors and systematic review of screening approaches, factors that increase malignancy risk include dermatomyositis subtype (risk ratio, 2.21), older age (weighted mean difference 11.19), male gender (RR, 1.53), dysphagia (RR, 2.09), cutaneous necrosis (RR, 2.73), and positive anti-TIF-1gamma (RR, 4.41).

Factors associated with a decreased risk of malignancy include polymyositis (RR, 0.49), clinically amyopathic dermatomyositis subtypes (RR, 0.44), Raynaud’s phenomenon (RR, 0.61), interstitial lung disease (RR, 0.49), very high serum creatine kinase (WMD –1189.96) or lactate dehydrogenase levels (WMD –336.53), and anti-Jo1 (RR, 0.45) or anti-EJ (RR, 0.17) positivity.

The analysis also found that CT scanning of the thorax, abdomen and pelvis appeared to yield a high proportion of underlying asymptomatic cancers. Limited evidence relating to the utility of tumor markers and 18F-FDG PET/CT was available.

As for treatment, the use of tofacitinib for cutaneous lesions of dermatomyositis has been suggested in various studies. In a recent open-label study of 10 patients with dermatomyositis who took extended release the JAK inhibitor tofacitinib 11 mg daily for 12 weeks, half experienced moderate improvement in disease activity, and the other half experienced minimal improvement. JAK inhibitors have been used in patients with juvenile dermatomyositis.

Dr. Callen’s treatment approach with dermatomyositis patients includes recommendations for sunscreens and protective clothing, plus assessment of vitamin D levels. “I will use topical emollients, corticosteroids, and calcineurin inhibitors,” he said. “Antimalarials might be used. I generally reach for methotrexate or mycophenolate mofetil relatively early. IVIG has also been studied.” Off-label therapies that have been used include dapsone, thalidomide, leflunomide, sirolimus, chlorambucil, etanercept, infliximab, rituximab, apremilast, tofacitinib, lenabasum, and low-dose naltrexone.

Dr. Callen disclosed that he is a consultant to Genentech and is a member of the safety monitoring committee for Principia Biopharma. He holds equity in Celgene, Pfizer, 3M, Johnson & Johnson, Merck, Abbott Laboratories, AbbVie, Procter & Gamble, Gilead, Allergen, and Amgen.

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