Assessment of Dimensions on Baseline Magnetic Resonance Imaging of Soft Tissue Sarcomas: Best Method to Estimate Tumor Size and Improve Prognosis

Purpose or Learning Objective: Soft tissue sarcomas (STS) are rare mesenchymal ubiquitous malignancies, with the thigh the most common location. The longest diameter (D_max) at baseline is an independent prognostic factor for STS patients and used in the SARCULATOR nomogram and Response Evaluation Criteria in Solid Tumors v.1.1. However, few studies have compared the performance of alternative measurements. Our aim was to determine which baseline dimensional assessment of STS of the thigh provides the best prognostic prediction.

Methods or Background: Two expert radiologists reviewed the baseline magnetic resonance imaging (MRI) of patients who underwent surgery at a sarcoma reference center between 2000 and 2017.

All patients underwent function-sparing surgery with negative surgical margins and a histologic grade assessment according to the Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC) system by expert pathologists.

High-field MRI included T1- and T2-weighted imaging (without and with fat suppression). Radiologists measured D_max, each plane's maximum diameter, and their sum (D_sum), and volume using the ellipsoid formula. The time spent on each measurement was monitored. Kaplan-Meier analysis and the log-rank test were used to estimate predictors for local recurrence (LR)-free survival and overall survival (OS). Multivariable analyses for LR and OS were based on cause-specific hazards and performed by Cox regression models.

Results or Findings: A total of 548 patients were enrolled in this study (mean age: 57 years). The mean follow-up time was 32 months (range: 4–269 months). Most STS were grade 3 (421/548 patients [79.6%]). R0 margins were obtained in 93.3% of cases. Size estimation results were mean D_max (10 cm), mean D_sum (22.5 cm), and mean volume (189.8 cm³). Mean time spent for each measurement was 1.9 minutes; the local recurrence rate was 19.1% at 5 years and 41.4% at 10 years. In multivariable analysis, volume, FNCLCC grade, and status of margins were independent prognostic factors for LR. The estimated OS was 73.1% (95% confidence interval [CI], 68.2–78.0%) at 5 years and 63.2% (95% CI, 56.4–70.0%) at 10 years. D_max, D_sum, FNCLCC grade, age, metastasis at presentation, and chemotherapy administration were independent prognostic factors for OS.

Conclusion: Both D_sum and volume, in addition to the D_max, could help radiologists obtain a reliable assessment of tumor size and aid clinicians with patient prognostication.

Publication History

Article published online:
26 May 2023