(P 358) RADIOMIC EVALUATION OF MRIS IN PATIENTS WITH SOFT TISSUE SARCOMA TREATED WITH STEREOTACTIC BOSY RADIATION THERAPY

Objective: Treatment of soft tissues sarcomas (STS) is complex and utilizes multiple neoadjuvant modalities including chemotherapy and/or radiation therapy. Stereotactic body radiation therapy (SBRT) delivers larger doses per fraction in a reduced number of fractions compared to conventional radiation therapy which is convenient for patients. Abundant literature shows that radiomics correlates with soft tissue tumor biologic aggressiveness and treatment response. This study analyzed whether certain radiomic features of MRI imaging correlate with histologic percent necrosis after SBRT.

Methods: In this retrospective single-center study, patients (age ≥18 years) were included if they presented with STS diagnosed between 2017 and 2023 with a pre- and post- radiation contrast enhanced MRI study. All patients received SBRT in 5 fractions to a median dose of 32 Gy (30-40 Gy). Radiomic variables tested include long axis, short axis, volume, uniformity, skewness, entropy, intensity, and kurtosis. Pre- and first post-treatment values were compared using Wilcoxon signed rank tests. Correlation between differences in values and histologic necrosis percentage were also calculated.

Results: A total of 10 patients were included in this analysis. 5 patients were women. 8 patients identified as Hispanic, 1 as Black, and 1 as non-Hispanic. Most patients (80%) had grade III tumors with a median size of 8.1 cm (3.2-12.3 cm) located in the extremity (70%). No variable tested (long axis, short axis, volume, uniformity, skewness, entropy, intensity, and kurtosis) demonstrated a P value < 0.05 indicating no statistically significant change between pre- and post-treatment MRIs. Pearson correlation coefficients revealed a moderate correlation between histologic percent necrosis and change in uniformity at r = -0.65.

Conclusion: No statistically significant radiomic difference was observed between pre- and post-treatment MRI imaging. Change in uniformity may represent increasing necrosis as tumor undergoes treatment effect.