Recurrent and new primary cancer risk in adult patients with idiopathic inflammatory myositis and a history of malignancy

OBJECTIVES: In adult patients with idiopathic inflammatory myopathies (IIM) and a history of cancer, the risk of subsequent cancer is unclear. We describe our centre's experience with recurrent and new primary cancer development after IIM symptom onset. METHODS: A retrospective cohort study was conducted at The Johns Hopkins Myositis Center, analysing adult IIM patients enrolled from 2003 to 2024 with a documented cancer history. Patients were categorised into three groups: 1. remained cancer-free, 2. had cancer recurrence, or 3. developed a new primary cancer. RESULTS: Among 2,476 IIM patients, 280 (11%) had a cancer history, with 39 (14%) diagnosed within the 3 years prior to IIM symptom onset. Of these, 29 (74%) remained cancer-free after symptom onset over a median follow-up period of 5.5 (IQR 6.7) years. Six patients (16%) experienced cancer recurrence, and four (10%) developed a new primary cancer after IIM symptom onset. The median time from index cancer to recurrence was 2.4 (IQR 1.6) years, whereas the time from index cancer to new primary was 1.4 (IQR 1.0) years. Of the ten patients who developed either recurrence or a new primary cancer after IIM symptom onset, all were diagnosed within the first three years after IIM symptom onset. CONCLUSIONS: In our tertiary referral centre, approximately one quarter of adult IIM patients who had a cancer diagnosis in the three years before IIM onset went on to develop an additional malignancy, either a recurrence or a new primary.