(P 303) SMALLER SARCOMAS AT HIGHER RISK FOR POSITIVE SURGICAL MARGINS: A PARADOX OF PROGNOSTIC FACTORS

Objective: Given the prognostic importance of margin status after sarcoma resection, the goals of this study were to characterize the variables that predict a higher risk of positive margins after first resection.

Methods: Patients undergoing their first Soft Tissue Sarcoma (STS) resections between 2015 and 2021 were identified at a single institution using ICD-10 coding. Electronic Health Records (EHRs) were reviewed for patient age, sex, BMI, and tumor region; pathology reports were examined for histologic subtype, histologic grade, and pathologic stage. Age was categorized as < 50 or > 50, BMI as < 30 (normal) or > 30 (obese), and tumor region as upper extremity (UE), lower extremity (LE), pelvis, and trunk. Using the 8th ed. AJCC staging for soft tissue sarcomas, size was defined as small (pT1 and pT2) and large (pT3 and pT4), and grade was categorized as low grade (G1) and high grade (G2 and G3). Univariate analysis was completed using risk ratios. Variables found to be significant on univariate analysis were incorporated into a multivariate logistic regression analysis and the resulting adjusted odds ratios were used to calculate risk ratios.

Results: Two hundred-forty patients with STS were included in the analysis. The distribution of STS histologic subtypes is demonstrated in Table 1. On univariate analysis, BMI, age, and non-UE tumor locations (LE, pelvis, trunk) were not significant predictors of positive margin status. Significant predictors included low tumor size, low grade, and upper extremity location (Table 2). Table 2 also examines these risk factors for different STS subgroups, including various grades, locations, and tumor sizes. These results demonstrate that tumor size was a risk factor for positive surgical margins regardless of tumor location (UE, non-UE) or whether the tumor was high grade. Tumor size was not a significant predictor for low grade tumors, which is likely related to the small sample size of the low grade, large size comparison group. Likewise, on multivariate logistic regression, tumor size remained a predictor for positive margins when including grade and location (p = 0.0172), although low grade and upper extremity location were no longer significant predictors (Table 3).

Conclusion: Although small tumor size is considered a favorable prognostic factor, this analysis uniquely demonstrates its association with positive surgical margins. This was significant even for high grade tumors and regardless of tumor location. These results suggest that wider margin resections may be advisable for small soft tissue sarcomas.

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