Background/Purpose: To examine the clinical features and prognosis of cancers associated with active myositis and to compare them with cancers found in patients with myositis but unrelated to myositis activity.      

Methods: Medical records of 289 patients who had been diagnosed as having polymyositis or dermatomyositis according to Bohan and Peter criteria were reviewed to identify fifty two cancer cases. Patients were screened for malignancies at the diagnosis of myositis but active cancer screening was not done during follow-up unless suspicious symptoms developed or their myositis worsened. Cancers were defined to be associated with active myositis if they were present during active phase of myositis (group A). If cancers were not detectable during active phase of myositis, they were defined to be unrelated to myositis activity (group B).

Results: Thirty patients were included in group A consisting of those who developed myositis and cancer together (n =25), whose myositis recurred with cancer development (n=2), or who developed myositis when their cancers progressed/recurred (n=3). Twenty two patients in group B were comprised of those who developed myositis during remission state of cancers with no further relapse of cancer (n=6) or whose cancers were detected during remission state of myositis with no further relapse of myositis (n=16). Group A tended to be male (14/30 vs 5/22, p=0.077) and had an older age at myositis diagnosis compared with group B (60.5±11.1 vs 49.3±16.6 years, p=0.022). Group A patients had shorter intervals between the diagnoses of myopathy and cancer (5.4±9.0 vs 71.6±46.6 months, p<0.001); 90% of cancers in group A developed within 1 year of myositis diagnosis whereas 90% in group B beyond 1 year. Muscle power grades and enzyme levels were not significantly different between the two groups at baseline. Dysphagia was more frequent (p=0.002) and interstitial lung disease less frequent (p=0.001) in group A. Notably, stages at cancer diagnosis were far advanced in group A (stage 3 and 4, 24/29 vs 7/22, p<0.001). Fewer patients in group A achieved normal muscle power during their course of myositis than in group B (p=0.036). The recovery to normal muscle power was associated with induction of cancer remission (p=0.036). Group A patients showed poor survival compared to group B patients (hazard ratio for mortality [95% confidence interval], 7.4 [2.6-21.2], p<0.001), which was still significant when adjusted for age and gender (4.3 [1.5-12.7], p=0.008 by Cox regression model).  

Conclusion: In patients with myositis, clinical features of cancers associated with active myositis were distinctive from those of cancers unrelated to myositis activity. The former were found to develop within 1 year of myositis in contrast to the latter, and to be more advanced at diagnosis. The outcome of associated myositis in the former cases was worse in terms of muscle power recovery. Successful cancer treatment was associated with better outcome of myositis. Patients who had cancers associated with active myositis showed poor survival compared to those who had cancers unrelated to myositis activity.

---

« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-and-prognosis-of-malignancies-associated-with-active-myositis/