В данном разделе указаны критерии оценки клинической значимости применения дорогостоящей противоопухолевой лекарственной терапии в соответствии со шкалой, разработанной экспертной группой (см. стр. 7). В тексте они обозначены, как магнитуда клинической значимости (МКЗ).

Introduction: The main current approach to the treatment of patients with resectable cancer of the stomach and gastroesophageal junction (GEJ) is perioperative FLOT chemotherapy. The mFOLFIRINOX regimen has been shown to be effective and safe in disseminated adenocarcinoma of the stomach and GEJ. This article presents preliminary results of the efficacy and safety assessment of perioperative FOLFIRINOX chemotherapy in patients with resectable cancer of the stomach and gastroesophageal junction.Materials and Methods: The FOLFIRINOX / FLOT study is a phase 2 / 3 open-label, randomized trial. Study enrollment was started in January 2019 and is currently ongoing. The inclusion criteria are: histologically confirmed resectable adenocarcinoma of the stomach or gastroesophageal junction, Siewert types II–III, clinical stage cT4aN0M0, cT1–4N1–3M0 or cT2–4N0–3M0, with total or subtotal involvement of the stomach. The following regimens were used for perioperative chemotherapy: FLOT — docetaxel 50 mg / m2 on day 1, oxaliplatin 85 mg / m2 on day 1, leucovorin 200 mg / 2 on day 1, 5FU 2600 mg / m2 × 24 hours starting on day 1, or mFOLFIRINOX — irinotecan 180 mg / m2 on day 1, oxaliplatin 85 mg / 2 on day 1, leucovorin 200 mg / m2 on day 1, 5FU 250 mg / m2 bolus on day 1 and then 2200 mg / m2 × 48 hours on day 1. The primary endpoint was 5‑year overall survival.Results: All planned preoperative courses of chemotherapy had been administered to 25 (86 %) patients in the FLOT group (n = 29) and 22 (92 %) patients in the FOLFIRINOX group (n = 24). Four (12 %) and 2 (8 %) patients in the FLOT and FOLFIRINOX groups, respectively, discontinued the treatment. The surgical staging was used in 48 patients (91 %) (25 [86 %] in the FLOT group and 23 [96 %] in the FOLFIRINOX group). Complete tumor regression (Mandard grade 1) had been achieved in 4 patients (2 [7 %] in the FLOT group and 2 [8 %] in the FOLFIRINOX group). Postoperative complications were detected in 2 patients (8 %) in the FLOT group and 4 (17 %) in the FOLFRIRNOX group. Thirty-three patients (62 %) received all scheduled postoperative treatment courses (n = 19, 66 % for FLOT and n = 14, 58 % for FOLFIRINOX).Conclusions: The preliminary results of the FOLFIRINOX / FLOT study showed comparable tolerability of the regimens and comparable complete pathological response rates. However, there was a higher incidence of postoperative complications detected among patients who received the FOLFIRINOX regimen compared to the FLOT group.

Introduction. Glycans play an important role in the pathogenesis of malignant neoplasms, including stomach cancer. In recent years, the attention of many researchers has been drawn to mannose (Man) – hexose, which is an indispensable component of all N-chains of glycoproteins involved in both normal physiological and pathological processes. Aim. To investigate the role of innate immunity factors and ways to influence them through mannose and mannose-containing glycans in gastric cancer patients. Materials and methods. Data on the role of mannose – one of the key monosaccharides in the formation of glycoprotein N-chains – and its binding receptors (mannose receptor, mannose-binding lectin, antibodies) in gastric cancer since 2006 are presented. Levels of anti-glycan antibodies in blood serum samples of 235 gastric cancer patients and 76 healthy donors were evaluated using a glycochip. Results. It has been shown that the level of IgM-class antibodies to Manβ – the core part of N-glycans – in gastric cancer patients is significantly lower compared to the donor group, regardless of age (p = 0.0001). To assess the effect of age on the levels of antiglycan antibodies, patients were divided into two subgroups – before and after 45 years. In the group under 45 years of age, significant differences in the levels of antiglycan antibodies to Manβ persisted, while significant differences in the levels of antiglycan antibodies to Manβ1-4GlcNAcβ were not observed. when comparing groups of patients and donors older than 45 years, the levels of antibodies to Manβ and Manβ1-4GlcNAcβ were significantly higher only in donors. Conclusion. Deficiency of humoral immunity may be one of the key factors in the initiation and progression of carcinogenesis in humans. In our work, in patients with stomach cancer, we revealed a deficiency of antiglycan antibodies to Manβ and to Manβ1-4GlcNAcβ – core fragments of N-chains of glycoproteins, and the deficiency increased with age. The results of the study are a promising platform for further research aimed not only at studying the role of anti-mannose antibodies, but also at developing approaches to adoptive immunoprophylaxis.

Рак желудка (РЖ) характеризуется агрессивным течением и является одной из ведущих причин смерти от онкологических заболеваний. Стандартные схемы лечения не всегда эффективны при этом заболевании, поэтому разработка новых подходов терапии и поиск предиктивных маркеров представляется актуальной научной задачей. Перспективными терапевтическими мишенями при злокачественных новообразованиях являются иммунные контрольные точки (ИКТ). Для понимания патогенеза и оптимизации терапии активно исследуется вклад ИКТ в процессы опухолевой прогрессии. В данном исследовании на выборке пациентов с микросателлитно стабильным фенотипом опухоли РЖ были изучены уровни экспрессии генов ИКТ и их коэкспрессия с генами, вовлеченными в эпителиально-мезенхимальный переход. Проведена оценка ассоциации экспрессии этих генов с клиническими характеристиками РЖ. Показано, что для низкодифференцированных опухолей характерно понижение экспрессии генов CD276 и PVR (p<0,05). Также обнаружено, что развитие метастазов ассоциировано с повышением уровня экспрессии гена TDO2. В случае неметастатического РЖ была выявлена корреляционная связь между уровнями экспрессии генов CD44 и CD276. В группе метастатического РЖ корреляционная связь уровней экспрессии выявлена между генами ADAM17, PVR, CD276 и генами CD44, SNAI1. Полученные данные дополняют представление о молекулярно-генетических механизмах, регулирующих прогрессию опухоли, и могут внести вклад в разработку новых терапевтических подходов, предполагающих совместное ингибирование генов, коэкспрессия которых является особенностью данной нозологии. Gastric cancer (GC) is an aggressive tumor that is one of the leading causes of death from cancer. Treatment regimens are not often effective for this disease, so the development of new approaches to therapy and the search for predictive markers seems to be an urgent scientific task. Immune checkpoints (ICs) are promising therapeutic targets for malignant neoplasms. To understand the pathogenesis and optimize therapy, the role of ICs in tumor progression is being actively studied. In this study, IC gene expression levels and their co-expression with epithelial-mesenchymal transition-related genes were examined in a sample of patients with a microsatellite stable GC tumor phenotype. The association of the expression of these genes with the clinical characteristics of GC was assessed. It was found that the expression of the CD276 and PVR genes was reduced in low-differentiated tumors (p < 0.05). The development of metastases is associated with an increased level of TDO2 gene expression. In non-metastatic GC, a correlation was found between the expression levels of the CD44 and CD276 genes. In metastatic GC, a correlation of expression levels was found between the ADAM17, PVR, CD276 genes and the CD44, SNAI1 genes. The findings add to the understanding of the molecular genetic mechanisms that regulate tumor progression and may contribute to the development of new therapeutic approaches involving mutual inhibition of genes.

Gastric cancer is one of the most common malignancies worldwide. Approximately 10 % of patients with gastric cancer are characterized by accumulation of gastric cancer cases in their family. The hereditary forms of gastric cancer account for 1–3 % of all gastric cancer cases. Hereditary diffuse GC syndrome is caused by germline mutations in CDH1 gene and determines a high risk of developing diffuse GC and lobular breast cancer. In this article, we present a clinical case of a 41-year-old patient with diffuse gastric cancer, who was found to be a carrier of novel germline mutation in the CDH1 gene. Next-generation sequencing (NGS) has facilitated an identification of CDH1 c.1596G>A genetic variant, thus enabling an accurate clinical diagnosis hereditary diffuse gastric cancer.

Personalization of gastric cancer (GC) treatment is an urgent problem because of the clinical heterogeneity and aggressive course of the disease. Four GC subtypes were isolated based on molecular characteristics by The Cancer Genome Atlas researchers in 2014: Epstein-Barr virus positive (EBV+), microsatellite unstable (MSI), chromosomally unstable (CIN), and genomically stable (GS). There is no unified method to detect the CIN and GS subtypes today, while MSI and EBV status assessments are used routinely and are of great clinical importance. A total of 159 GC samples were tested for MSI, EBV DNA, and somatic mutations in codons 12-13 (exon 2), 61 (exon 3), and 146 (exon 4) of the KRAS gene; codons 597-601 (exon 15) of the BRAF gene; and codons 542-546 (exon 9), 1047-1049 (exon 20) of the PIK3CA gene. EBV+ GC was detected in 8.2% of samples; and MSI, in 13.2%. MSI and EBV+ were found to be mutually exclusive. The mean ages at GC manifestation were 54.8 and 62.1 years in patients with EBV+ and MSI GCs, respectively. EBV+ GC affected men in 92.3% of cases, 76.2% of the patients were older than 50 years of age. Diffuse and intestinal adenocarcinomas were diagnosed in 6 (46.2%) and 5 (38.5%) EBV+ cases, respectively. MSI GC equally affected men (n = 10, 47.6%) and women (n = 11, 52.4%). The intestinal histological type was the most prevalent (71.4%); the lesser curvature was affected in 28.6% of the cases. The E545K variant of PIK3CA was observed in one EBV+ GC case. A combination of clinically significant variants of KRAS and PIK3CA was found in all MSI cases. The BRAF V600E mutation, which is specific to MSI colorectal cancer, was not detected. The EBV+ subtype was associated with better prognosis. The five-year survival rates were 100.0 and 54.7% for MSI and EBV+ GCs, respectively.

To date, gastric cancer patients still have a poor prognosis. Current endoscopic or surgical treatment modalities are radical only for early gastric cancer (T1). Curability dramatically declines as tumor invasion progresses and lymph node metastasеs appear. In Europe and North America, the 5-year overall survival rate of patients with stage T2–4 cancer is 20 % [1]. Combination therapy for gastric cancer is being extensively studied to improve the treatment outcomes [2–6]. Currently, perioperative chemotherapy with FLOT regimen is the mainstay of resectable gastric cancer treatment in Europe. FLOT4-AIO randomized study has shown that the FLOT regimen was associated with significant increase in the median overall survival (50 versus 35 months), disease-free survival (18 versus 30 months) and R0 resection rate compared to ECF / ECХ regimen.In this work we evaluated the efficacy and toxicity of perioperative FLOT regimen in patients with gastric cancer and gastroesophageal junction cancer type I–III cT4aN0M0, cT1–4N + M0, using a prospective database of patients treated at the N. N. Blokhin Russian Cancer Research Center.

Introduction. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract the character diagnostic feature of which is CD117 (KIT) expression. GISTs are clinically diverse and have different genetic alterations that may have predictive and prognostic significance.Aim – the study of clinical, morphological and genetic features of GISTs to assess the overall survival (OS) of patients with various profiles of genetic disorders for elucidation the factors contributing to prognosis.Materials and methods. A total 244 GIST patients who received combined treatment were enrolled in the study and their clinical characteristics and mutational status of KIT, PDGFRA, BRAF were analyzed. SDH-deficient GISTs were detected using IHC-analysis of SDHB expression.Results. Stromal tumors developed in stomach (50 %), small intestine (37.7 %), colon or rectum (8.6 %), esophagus (0.4 %) and extraorganically (EGIST, 5.7 %). Overall survival correlated with gastric site (p = 0.005), tumor size <10 cm (p = 0,0001) and mitotic count HPF< 10 / 50 (p = 0.007). KIT mutations were found in 168 (68.9 %) and PDGFRA – in 31 (12.1 %) of GISTs, 14 novel mutations were detected. Mutations in KIT exon 11 were found in 140 (57.4 %) tumors, 10-year OS, 51 %, median 124 months. Patients with deletions had lower OS than patients with substitutions or duplications in KIT exon 11 (p = 0,023). The lowest OS was in patients with primary mutations in KIT exons 13 or 17 (median 28 months) and duplications in KIT exon 9 (median 71 months). There was a low OS of young patients with homozygous KIT mutations, mutations that begin in intron and two simultaneous KIT mutations. GISTs with PDGFRA mutations were located in stomach and had no metastases, 10-year OS, 63 %, median 175 months. KIT / PDGFRA mutations were not observed in 45 (18.4 %) patients (wild-type GIST), 10-year OS, 59 %, median 250 months. Wild-type GISTs with BRAF, NF1 mutations and SDH deficiency were detected. The better OS was demonstrated by patients with BRAFV600E (10-year ОS, 84 %, median 97 months) and SDH deficiency (10-year and 15-year OS, 82 %).Conclusion. Genetic analysis is necessary to clarify GIST prognosis and predict the effectiveness of targeted therapy. The clinical, morphological and genetic diversity of GISTs was confirmed. Wild-type GISTs with BRAF mutations and SDHdeficiency were identified in the Russian population for the first time. The long-term 10- и 15-year OS of GIST patients were evaluated.

Primary pancreatic leiomyosarcoma belongs to a rare group of malignant soft tissue tumors. we present a clinical case of a 61-year-old patient who underwent hemipancreatectomy with splenectomy for a pancreatic tumor in 2018. Histological and immunohistochemical studies confirmed the diagnosis of leiomyosarcoma. for three years, the patient has been observed at the N.N. Blokhin National Medical Research Center of Oncology of ministry of Health of Russia without signs of progression.

Currently, with duodenal tumor lesion (duodenum), the possibility of performing economical operations that significantly improve the immediate results and quality of life of patients is increasingly being considered as an alternative to gastropancreatoduodenal resection. using the example of clinical observation, the article presents a new type of economical surgical intervention – duodenectomy with preservation of the peripapillary flap. The operation was performed in a patient with cancer of the resected stomach with a low spread of the tumor along the wall of the duodenum. At the control examination 9 months after the operation, the patient’s condition is satisfactory, without signs of impaired biliodynamics and passage of food through the intestinal tube. The proposed method differs from the existing prototype (papilloservative duodenectomy) by preserving the peripapillary flap of the duodenal wall.The insertion into the jejunum of not the fater papilla, but the surrounding wall of the duodenum eliminates its deformation and violation of patency and provides greater reliability of the formed suture, and the preservation of the small duodenal papilla with an additional pancreatic duct of Santorini can help reduce the frequency of postoperative pancreatitis and pancreonecrosis. In addition to cases of low lesions of the duodenum in gastric cancer, the method can be used in patients with non-epithelial and neuroendocrine tumors, as well as in secondary tumor invasion of the duodenum from the outside. The criterion limiting the performance of this type of operation is the distance from the edge of the tumor to the fater papilla less than 2.0–2.5 cm.Duodenectomy with preservation of the peripapillary flap can be considered as a way to improve the safety and quality of life in the surgical treatment of patients with a tumor lesion of the duodenum.

Gastrointestinal stromal duodenal tumors are rare diseases of small intestine. Duodenal GISTs may be giant; these neoplasms can also simulate malignancies of other organs. These features result diagnostic and treatment mistakes. Neoadjuvant therapy with imatinib results tumor shrinkage and ensures organ-sparing surgery. We report duodenal GISTs in patients with primary diagnosis «retroperitoneal tumor», «pancreatic cyst» and «retroperitoneal abscess», who were treated at the Blokhin National Cancer Research Centre in 2019-2020.

OBJECTIVE:To evaluate the immediate and long-term results of surgical and combined treatment of patients with duodenal stromal tumors.MATERIAL AND METHODS:There were 47 patients with duodenal stromal tumors for the period 2002-2019. All patients underwent treatment at the Blokhin National Cancer Research Center. Six patients had metastatic disease, 2 ones - a rare syndrome of duodenal stromal tumor associated with neurofibromatosis type 1, other 39 patients had a localized and locally-advanced disease. Surgical treatment was performed in 37 patients (limited resections (LR) in 24 cases and gastropancreaticoduodenectomy in 13 cases).Incidence of postoperative complications was significantly lower after limited resections compared to gastropancreaticoduodenectomy (22.2% (6/24) vs. 61.5% (8/13), respectively). Severe complications (Clavien-Dindo grade 3) occurred in 4.2% (1/24) vs. 15.3% (2/13) of patients, respectively. Postoperative mortality was absent in both groups. We observed no significant differences in long-term results. Overall 5-year survival was 91% and 70% (p=0.5960), 5-year recurrence-free survival - 65 and 70% (p=0.6226), respectively.CONCLUSION:Considering similar survival rates, lower postoperative morbidity and better quality of life, limited duodenal resections are preferred for duodenal stromal tumors.

Рак желудка (РЖ) является одной из существенных причин смертности от онкологических заболеваний. Неблагоприятный прогноз при РЖ в значительной мере связан с метастазированием опухоли. Экспрессия генов и микроРНК может являться источником биомаркеров, сигнализирующих о повышенном риске метастазирования опухоли. Выявление генов, ассоциированных с метастазированием опухоли, и создание прогностической панели микроРНК и генов, является весьма актуальным. Нами исследована экспрессия микроРНК miR-34a и miR -335 и генов FGFR2, VEGFR1 и NRP1 при диссеминированном РЖ в сравнении с не метастазирующими опухолями РЖ. Охарактеризована ассоциация с развитием отдаленного метастазирования, указывающая на их качество как кандидатов в маркеры. Сформированы панели, включающая гены и микроРНК - кандидаты в маркеры прогноза. Проведенный сравнительный анализ панелей позволил выбрать в качестве наиболее эффективной панель, включающую miR335/ VEGFR1 /FGFR2, которая демонстрирует наилучшие показатели как кандидат прогноза метастазирования, особенно по значению отношения шансов ОR = 143 и RR = 7,1. Gastric cancer (GC) is one of the significant causes of mortality from cancer. An unfavorable forecast for GC is largely associated with tumor metastasis. Expression of genes and microRNAs can be a source of biomarkers that signal the increased risk of tumor metastasis. The detection of genes associated with tumor metastasis, and the creation of a candidate prognostic panel of microRNAs and genes is very relevant. We investigated the expression of MIR-34A and MIR -335 microRNA and FGFR2, VEGFR1 and NRP1 genes with disseminated gastric cancer in comparison with non-metastatic GC tumors. Association is characterized with the development of remote metastasis, indicating their quality as candidates for markers. Panels are formed, including genes, and microRNAs - candidates for prognostic markers. A comparative analysis of the panels allowed to be characterized as the most efficient panel, including MIR335/VEGFR1/FGFR2, which demonstrates the best indicators as a candidate for the metastasis prediction panel, especially the value of the ratio of the chance of OR = 143 and RR = 7.1.

An association was found between reduced expression of miR-34a, miR-146a with both metastasis to regional lymph nodes (relative risk RR=10.50 and RR=5.25, respectively) and the development of distant metastases (RR=9.50 and RR=4, 40, respectively) in gastric cancer. They are excellent classifiers: AUC>0.9 for both miRNAs. The association of miR-335 expression with metastasis to the lymph nodes is much weaker, but it is also a good classifier for identifying a group with distant metastasis (RR=5.90). A correlation was found between the expression of miR-34a and miR-146a during metastasis, which is absent in non-metastatic tumors. Thus, miR-34a, miR-146a, and miR-335 miRNAs can be proposed as candidates for biomarkers of the risk of gastric cancer metastasis.

The expression levels of miR-146a and the target gene of this miRNA, NF-kB, in gastric cancer (GC) samples at different stages of metastasis development were studied. The expression of miR-146a in the samples of the GC decreased with the involvement of regional lymph nodes in the metastatic process. A negative correlation was found between the expression level of miR-146a and the number of regional lymph nodes damage (Spearman’s correlation coefficient (R) was R = - 0.61; p 0.005). On the contrary, NF-κB gene expression increased with lymph node metastases. An inverse correlation was found between miR-146a and NF-κB (R = -0.76; p 0.03). The first detected negative correlation of expression between miR-146a and NF-κB may indicate activation of the NF-κB signaling pathway in GC cells with a decrease in miR-146a expression. Apparently, this signaling pathway is important in the development of metastases of gastric cancer.

Retroperitoneal leiomyosarcomas (RpLMS) are highly aggressive tumors, which are characterized by poor prognosis and resistance to chemotherapy. Targeting tumor-specific molecular pathways have become a rapidly expanding field in drug development to increase efficacy of treatment of LMS. Here we present a case report of rapidly progressive RpLMS with gene mutations of key molecular pathways, which have not previously described in the literature. A 61-year-old man was admitted to our hospital with complaints of abdominal pain and fever. Radiological examination revealed retroperitoneal leiomyosarcoma, which was histologically confirmed by core-biopsy. The patient underwent radical (R0) en-bloc resection of tumor with left hemicolectomy, left total nephrectomy, left total adrenalectomy and distal subtotal pancreatectomy. Pathological assessment of the tumor revealed G3 leiomyosarcoma. The patient did not receive adjuvant therapy. Disease progression (local recurrence and pulmonary metastases) occurred 3 months after surgery, and the patient died 6 months after surgery. Immunohistochemical study revealed positive PD -L1 expression in tumor cells. The percentage of PD -L1- expressing cells was 30 %. Molecular-genetic testing allowed identification of somatic mutations in genes, such as PIK3CA, ALK, EGFR, ERBB, ESR1 and PD GFRA and confirmation of microsatellite stable status (MSS) of the tumor. Further studies to investigate spectrum of mutations in RpLMS are of great interest, since they can allow identification of potential targets for more effective antitumor therapy and to improve treatment results.

Были изучены уровни экспрессии miR-146а и гена-мишени этой микроРНК - NF-kB в образцах рака желудка (РЖ) на разных этапах развития метастазов. Экспрессия miR-146а в образцах РЖ понижалась по мере вовлечения регионарных лимфоузлов в метастатический процесс. Была обнаружена отрицательная корреляция уровня экспрессии miR-146а со степенью поражения регионарных лимфоузлов (коэффициент корреляции по Спирмену (R) составил R = - 0,61; p=0,005). Напротив, экспрессия NF-kB повышалась при поражении лимфоузлов метастазами. Обнаружена обратная корреляция между miR-146a и NF-kB (R = -0,76; p=0,03). Впервые обнаруженная отрицательная корреляция экспрессии между miR-146a и NF-kB может указывать на активацию сигнального пути NF-kB в клетках РЖ при снижении экспрессии miR-146a. Видимо, этот сигнальный путь имеет значение при развитии метастазов РЖ. The expression levels of miR-146a and the target gene of this miRNA, NF-kB, in gastric cancer (GC) samples at different stages of metastasis development were studied. The expression of miR-146a in the samples of the GC decreased with the involvement of regional lymph nodes in the metastatic process. A negative correlation was found between the expression level of miR-146a and the number of regional lymph nodes damage (Spearman’s correlation coefficient (R) was R = - 0.61; p 0.005). On the contrary, NF-κB gene expression increased with lymph node metastases. An inverse correlation was found between miR-146a and NF-κB (R = -0.76; p 0.03). The first detected negative correlation of expression between miR-146a and NF-κB may indicate activation of the NF-κB signaling pathway in GC cells with a decrease in miR-146a expression. Apparently, this signaling pathway is important in the development of metastases of gastric cancer.

Background. Leiomyosarcoma is one of the most common types of soft tissue sarcomas. Radical surgical resection with subsequent adjuvant chemotherapy remain the most effective treatment approach. Immunotherapy based on inhibition of PD-L1 (programmed death ligand 1) or its receptor PD1 (programmed death 1) is considered a promising treatment option. Level of PD-L1 expression in tumor cells and presence of microsatellite instability (МSI) could be considered prognostic and predictive markers of disease progression and effectiveness of immunotherapy.The study objective is to determine PD-L1 expression level and МSI status in patients with retroperitoneal leiomyosarcomas and evaluate their effect on overall and recurrence-free survival.Materials and methods. The study included 57 patients with retroperitoneal leiomyosarcomas who underwent surgical or combination treatment. Analysis of clinical and morphological characteristics was performed; results of surgical treatment were researched. Evaluation of PD-L1 expression and MSI status was performed using immunohistochemical and molecular genetic analysis.Results. PD-L1 expression and MSI status were evaluated in 41 patients of 57. In 10 (24 %) of 41 cases, positive PD-L1 expression was observed (expression level 3–50 %). In 1 (2.4 %) patient, the primary tumor and metastatic lesion had low MSI level (MSI-low, MSI-L). Median follow-up was 31 months. In patients with positive PD-L1 expression, higher Ki-67 proliferative index was observed compared to patients with PD-L1 negative tumors (58.8 and 47.8 % respectively; р = 0.02), as well as significantly lower median overall survival for grade II tumors (30 and 105 months; p = 0.043). In grade III leiomyosarcomas, a trend towards lower median overall survival in patients with PD-L1‑negative tumors (31.0 months) compared to patients with PD-L1 expression (61.2 months) (р = 0.11) was observed.Conclusion. Among patients with retroperitoneal leiomyosarcomas, positive expression of PD-L1 was observed in 24 % (10 / 41) of cases and MSI-low status was found in 2.4 % (1 / 41) of cases. In patients with grade 2 tumors, positive PD-L1 expression is associated with significantly lower overall survival. PD-L1 expression in patients with retroperitoneal leiomyosarcomas could be considered a prognostic marker and a potential therapeutic target.