(P 360) MRI SURVEILLANCE PRACTICES AND RECURRENCE DETECTION IN EXTREMITY SOFT TISSUE SARCOMA: A RETROSPECTIVE STUDY

Objective: To analyze MRI surveillance and recurrence patterns in extremity soft-tissue sarcoma (STS) patients to optimize risk-stratified protocols and provide baseline metrics for alternative imaging modalities.

Methods: A retrospective review of 59 adults with extremity STS resected between 2010 and 2018, with a minimum follow-up of 5 years. Patient demographics, tumor characteristics, outcomes, and surveillance metrics were collected from their EMR. Univariate comparisons, logistic regression, Kaplan-Meier, and Cox models evaluated recurrence predictors and MRI surveillance patterns.

Results: The mean age was 59.9 ± 16.2 years with a mean tumor size of 9.7 ± 7.7 cm (range 0.5-30.0 cm). Histopathology showed 47.5% high-grade tumors and 10.2% R1 margins. The overall recurrence rate was 23.7% (14/59) at a median of 725 days (range 14-2,450 days). Patients underwent an average of 5.6 ± 3.8 MRIs (non-recurrence) and 7.1 ± 4.3 MRIs (recurrence) over a median follow-up of 6.2 years, with the first MRI occurring at 300 ± 273 days. Cox analysis revealed no association between MRI frequency and recurrence (HR = 1.003, p = 0.97). Tumor size independently predicted recurrence; every 1 cm increase in size increased odds by 24% (OR = 1.24, p = 0.028) and length of stay by 0.09 days (p = 0.026). Larger tumors were linked to shorter recurrence-free survival (log-rank, p = 0.002).

Conclusion: In this cohort, patients had an average of 6 MRIs over five years, with 23.7% experiencing recurrence at a mean of 2.5 years. This occurred in patients with larger tumors, longer hospital stay, and increased MRI utilization. Although MRI remains the gold standard, the lack of association between MRI frequency and outcomes challenges current imaging strategies. These findings support the implementation of risk-stratified surveillance protocols and the need for baseline imaging metrics to evaluate alternative imaging methods, like ultrasounds, which could reduce costs and improve access for underserved groups without sacrificing clinical effectiveness.