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P14. Refining Patient Selection for Pembrolizumab in Localized Soft Tissue Sarcoma of the Extremity: A Sarculator-Based Reanalysis of the Randomized SU2C-SARC032 Trial

Thursday, March 5, 2026
10:39 AM - 10:46 AM MST
Location: 101A-C
Introduction: To assess which stage III extremity/limb girdle soft tissue sarcoma (elgSTS) patients benefit most from adding pembrolizumab (P) to preoperative radiotherapy (RT) and surgery in the SU2C-SARC032 trial, using the Sarculator nomogram.


Methods: SU2C-SARC032 randomized grade 2-3 elgSTS to preoperative RT (50 Gy in 25 fractions) and surgery ± perioperative P (RT+P). In RT+P, P was given before, during, and after RT, then continued up to 14 cycles postoperatively. Sarculator was used to predict 10-year overall survival (pr-10y-OS) and distant-metastasis (DM) risk (pr-10y-DM), and predictions were classified as favourable (pr-10y-OS ≥60% or pr-10y-DM < 36.5%) and less favourable (pr-10y-OS < 60% or pr-10y-DM ≥36.5%). Actual outcomes were reported within these prediction groups. Disease-free survival (DFS) was compared with Kaplan–Meier/log-rank; DM incidence with Fine–Gray competing-risk regression with death as a competing risk.


Results: 122 patients were included (RT n=62; RT+P n=60). In the RT arm, DFS was higher but not significant, in patients with favourable vs less favourable predictions (24-month: 57% vs 48%; 36-month: 50% vs 42%; p=0.617). In the RT+P arm, DFS again trended higher with favourable predictions (24-month: 73% vs 60%; 36-month: 67% vs 53%; p=0.167). Across the cohort, RT+P produced a numerically greater improvement in DFS favourable predictions (24-month: 57% [RT] vs 73% [RT+P]; 36-month: 50% vs 67%; p=0.170) than in less favourable predictions (24-month: 48% [RT] vs 60% [RT+P]; 36-month: 42% vs 53%; p=0.563). Fine–Gray analysis showed less DM with RT+P in favourable predictions (24-month: 43% [RT] vs 23% [RT+P]; 36-month: 50% vs 27%; p=0.055) vs less favourable predictions (24-month: 45% vs 38%; 36-month: 51% vs 42%; p=0.564).


Conclusions: While no comparisons reached statistical significance, trends suggest that patients with favourable Sarculator-predicted outcomes may benefit more from adding perioperative P to preoperative RT and surgery. This is the first application of Sarculator in an immunotherapy-treated cohort, and these hypothesis-generating findings warrant investigation in larger, risk-adapted studies.

Learning Objectives:

  • Understand how the Sarculator nomogram can stratify prognosis in stage III extremity/limb girdle soft tissue sarcoma (elgSTS) and guide interpretation of clinical trial results.
  • Evaluate the potential differential benefit of adding perioperative pembrolizumab to preoperative radiotherapy and surgery in patients with favourable versus less favourable Sarculator-predicted outcomes.
  • Recognize the implications of integrating prognostic nomograms with immunotherapy trials to inform risk-adapted treatment strategies and future trial design in soft tissue sarcoma.