Correlation of radiological and histopathological response after neoadjuvant radiotherapy in soft tissue sarcoma

The aim of this study was to assess the association between radiological and histopathological response after neoadjuvant radiotherapy (nRT) in soft tissue sarcoma (STS), as well as the prognostic value of the different response evaluation methods on the oncological outcome. A retrospective cohort of patients with localized STS of the extremity and trunk wall, treated with nRT followed by resection were included. The radiological response was assessed by RECIST 1.1 (RECIST) and MR-adapted Choi (Choi), histopathologic response was evaluated according to the EORTC-STBSG recommendations. Oncological outcome parameters of interest were local recurrence-free survival (LRFS), disease metastases-free survival (DMFS), and overall survival (OS). For 107 patients, complete pre- and postoperative pathology and imaging datasets were available. Most tumors were high-grade (77%) and the most common histological subtypes were undifferentiated pleomorphic sarcoma/not otherwise specified (UPS/NOS, 40%), myxoid liposarcoma (MLS, 21%) and myxofibrosarcoma (MFS, 16%). When comparing RECIST to Choi, the response was differently categorized in 58%, with a higher response rate (CR + PR) with Choi. Radiological responders showed a significant lower median percentage of viable cells (RECIST p = .050, Choi p = .015) and necrosis (RECIST p < .001), and a higher median percentage of fibrosis (RECIST p = .005, Choi p = .008), compared to radiological non-responders (SD + PD). RECIST, Choi, fibrosis, and viable cells were not significantly associated with altered oncological outcome, more necrosis was associated with poorer OS (p = .038). RECIST, Choi and the EORTC-STBSG response score show incongruent results in response evaluation. The radiological response was significantly correlated with a lower percentage of viable cells and necrosis, but a higher percentage of fibrosis. Apart from necrosis, radiological nor other histopathological parameters were associated with oncologic outcomes.本研究旨在评估软组织肉瘤（STS）新辅助放疗（nRT）后影像学应答与病理学应答的相关性，以及不同疗效评价方法对肿瘤学结局的预后价值。本研究纳入接受新辅助放疗后行切除术的肢体及躯干壁局限性软组织肉瘤患者的回顾性队列。影像学疗效分别采用实体瘤疗效评价标准1.1版（RECIST 1.1，RECIST）及磁共振改良Choi标准（Choi）进行评估，病理学疗效则参照欧洲癌症研究与治疗组织-软组织肉瘤协作组（EORTC-STBSG）的推荐标准进行评价。本研究关注的肿瘤学结局参数包括无局部复发生存期（LRFS）、无远处转移生存期（DMFS）及总生存期（OS）。共计107例患者的术前及术后病理学、影像学完整数据集可供分析。多数肿瘤为高级别肉瘤（77%），最常见的组织学亚型为未分化多形性肉瘤/非特殊类型（UPS/NOS，40%）、黏液样脂肪肉瘤（MLS，21%）及黏液纤维肉瘤（MFS，16%）。对比RECIST与Choi标准，两类方法对58%的患者疗效分类结果不一致，且Choi标准的缓解率（完全缓解+部分缓解，CR+PR）更高。与影像学非应答者（疾病稳定+疾病进展，SD+PD）相比，影像学应答者的存活肿瘤细胞中位占比（RECIST：P=0.050；Choi：P=0.015）及坏死组织中位占比（RECIST：P<0.001）均显著更低，而纤维化组织中位占比则显著更高（RECIST：P=0.005；Choi：P=0.008）。RECIST、Choi标准、纤维化程度及存活肿瘤细胞占比均与肿瘤学结局无显著相关性；而更高的坏死组织占比则与较差的总生存期相关（P=0.038）。RECIST、Choi标准及EORTC-STBSG疗效评分在疗效评价中结果不一致。影像学应答与更低的存活肿瘤细胞占比、坏死组织占比及更高的纤维化组织占比显著相关。除坏死组织占比外，影像学及其他病理学参数均与肿瘤学结局无显著关联。