Predictive Biomarkers of Pathological Response to Neoadjuvant Radiochemotherapy for Locally Advanced Soft Tissue Sarcomas.

Purpose/objective(s) Soft tissue sarcomas (STS) is a large group of rare cancers which present high intratumoral heterogeneity. Thus, the assessment of response to the neoadjuvant treatment applied for locally advanced STS remains a challenge. We hypothesized that the pathological response (PR) could be predicted using biomarkers of the tumor microenvironment, hypoxia, and DNA damage. Materials/methods We analyzed prospectively collected core biopsy tissue samples from patients who received preoperative 5 × 5 Gy with doxorubicin-ifosfamide for marginally resectable high-grade STS in a phase II clinical trial. We have chosen tumor-infiltrating macrophages (TAMs) and intratumoral microvascular density (IMVD) as biomarkers for the tumor microenvironment. Hypoxia-inducible factor 1-alpha (HIF1A) expression was selected as a biomarker of intratumoral hypoxia. Double-strand DNA breaks were evaluated by expression of the phosphorylated form of H2A histone family member X (gH2AFX). Immunohistochemical analysis (CD163, CD68, CD105, CD34, HIF1A, gH2AFX) was evaluated by experienced sarcoma pathologists blinded to sample identification with a semi-quantitative method. We scored TAMs by counting the number of positive-staining macrophages per mm2: 0-none, 1-low, and 2-high. IMVD were counted in five randomly selected fields at 200x magnification (∼6.9 mm2), and a total number of microvessels included scoring scale: 1 (1-25), 2 (26-50), 3 (51-100), and 5 (> 500). HIF1A and gH2AFX were assessed in H-score scale, including intensity: 0-none, 1-weak, 2-moderate, 3-strong, and percentage of stained cells in each category (range: 0-300). All markers were studied preoperatively, while HIF1A was additionally assessed in postoperative tissues to define hypoxic microenvironment shift after therapy. PR to the treatment was classified using the European Organization for Research and Treatment of Cancer-Soft Tissue and Bone Sarcoma Group recommendations; grades A, B, C indicated good PR, whereas D and E suggested poor PR. Spearman rank correlation was used to measure the degree of association between biomarkers and PR. Results Nineteen patients were eligible for the analysis. We identified a good treatment PR in four cases (grades A = 1, B = 2, C = 1, D = 11, E = 4). High tumor infiltration with TAMs and high IMVD did not correlate with PR. High initial expression of HIF1A correlated with poor PR, whereas high expression of gH2AFX correlated with better PR (Tab. 1). We also confirmed decreased HIF1A expression after therapy between biomarkers and PR. Conclusion HIF1A (hypoxia degree) and gH2AFX (DNA damage extent) are candidate biomarkers for PR's prediction after neoadjuvant treatment in STS. Further evaluation in prospective studies is warranted.