Peptide Receptor Radionuclide Therapy (PRRT) is an emerging therapeutic option for pancreatic neuroendocrine tumors (PanNETs). A possible role for PRRT as a neoadjuvant agent is still largely undetermined, explored only in case reports or small case series. Likewise, the histopathological and immunophenotypic changes induced by PRRT are poorly characterized. In the present study, 24 patients who underwent neoadjuvant PRRT on the basis of their disease’s characteristics were retrospectively matched with 24 patients who underwent upfront surgery. A comprehensive morphological and immunohistochemical evaluation was conducted to identify the differences in the two groups. The most significant findings were that the total percentage of stroma increased significantly in patients who underwent PRRT (p < 0.0001) and the characteristics of the stroma were different in the two groups. The somatostatin receptors type 2A (SSTR2A) were retained in most patients (87%) after PRRT. The density of CD163+ M2-polarized macrophages was greater in the PRRT group (p = 0.022), and M2-polarized macrophages tended to assume an epithelioid morphology (p = 0.043). In the neoadjuvant PRRT group, none of the histological parameters considered were associated with progression-free survival (PFS). Neoadjuvant PRRT in PanNETs is associated with reduced tumor diameter, an increased percentage of stroma, preserved SSTR2A expression in most of the cases, and an increased CD163+ M2-polarized macrophages density.

中文翻译：

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新辅助肽受体放射性核素治疗（PRRT）后胰腺神经内分泌肿瘤的组织病理学和免疫表型变化。

肽受体放射性核素治疗（PRRT）是胰腺神经内分泌肿瘤（PanNETs）的新兴治疗选择。PRRT作为新辅助剂的可能作用仍未完全确定，仅在病例报告或小病例系列中进行了探讨。同样，PRRT诱导的组织病理学和免疫表型变化的特征也很差。在本研究中，根据其疾病特征，对24例行新辅助PRRT的患者与24例行前期手术的患者进行回顾性匹配。进行了全面的形态学和免疫组化评估，以鉴定两组之间的差异。最重要的发现是接受PRRT的患者中基质的总百分比显着增加（p <0.0001），并且两组间质特征不同。PRRT后，大多数患者（87％）保留了2A型生长抑素受体（SSTR2A）。PRRT组中CD163 + M2极化的巨噬细胞的密度更高（p  = 0.022），M2极化的巨噬细胞倾向于呈上皮样形态（p  = 0.043）。在新辅助PRRT组中，没有考虑的组织学参数与无进展生存期（PFS）相关。PanNETs中的新辅助PRRT与肿瘤直径减小，间质百分比增加，在大多数情况下保留的SSTR2A表达以及CD163 + M2极化的巨噬细胞密度增加有关。