Real-world implications of IMACS malignancy screening guidelines for idiopathic inflammatory myopathies: An evaluation of compliance and economic impact at a tertiary referral center

Aim: An inaugural set of consensus guidelines for malignancy screening in idiopathic inflammatory myopathy (IIM) were recently published by an international working group. These guidelines propose different investigation strategies based on "high", "intermediate" or "standard" malignancy risk groups. This study compares current malignancy screening practices at an Australian tertiary referral center with the recommendations outlined in these guidelines. Methods: We conducted a retrospective analysis of newly diagnosed IIM patients. Relevant demographic and clinical data regarding malignancy screening were recorded. Existing practice was compared with the guidelines using descriptive statistics; costs were calculated using the Australian Medicare Benefit Schedule. Results: Of the 47 patients identified (66% female, median age: 63 years [IQR: 55.5-70], median disease duration: 4 years [IQR: 3-6]), only one had a screening-detected malignancy. Twenty patients (43%) were at high risk, while 20 (43%) were at intermediate risk; the remaining seven (15%) had IBM, for which the proposed guidelines do not recommend screening. Only three (6%) patients underwent screening fully compatible with International Myositis Assessment and Clinical Studies recommendations. The majority (N = 39, 83%) were under-screened; the remaining five (11%) overscreened patients had IBM. The main reason for guideline non-compliance was the lack of repeated annual screening in the 3 years post-diagnosis for high-risk individuals (0% compliance). The mean cost of screening was substantially lower than those projected by following the guidelines ($481.52 [SD 423.53] vs $1341 [SD 935.67] per patient), with the highest disparity observed in high-risk female patients ($2314.29/patient). Conclusion: Implementation of the proposed guidelines will significantly impact clinical practice and result in a potentially substantial additional economic burden.