Experimental validation of the accuracy of robotic-assisted radioactive seed implantation for tumor treatment.

An experimental validation of a robotic system for radioactive iodine-125 seed implantation (RISI) in tumor treatment was conducted using customized phantom models and animal models simulating liver and lung lesions. The robotic system, consisting of planning, navigation, and implantation modules, was employed to implant dummy radioactive seeds into the models. Fiducial markers were used for target localization. In phantom experiments across 40 cases, the mean errors between planned and actual seed positions were 0.98 ± 1.05 mm, 1.14 ± 0.62 mm, and 0.90 ± 1.05 mm in the x, y, and z directions, respectively. The x, y, and z directions correspond to the left-right, anterior-posterior, and superior-inferior anatomical planes. Silicone phantoms exhibiting significantly smaller x-axis errors compared to liver and lung phantoms (p < 0.05). Template assistance significantly reduced errors in all axes (p < 0.05). No significant dosimetric deviations were observed in parameters such as D90, V100, and V150 between plans and post-implant doses (p > 0.05). In animal experiments across 23 liver and lung cases, the mean implantation errors were 1.28 ± 0.77 mm, 1.66 ± 0.69 mm, and 1.86 ± 0.93 mm in the x, y, and z directions, slightly higher than in phantoms (p < 0.05), with no significant differences between liver and lung models. The dosimetric results closely matched planned values, confirming the accuracy of the robotic system for RISI, offering new possibilities in clinical tumor treatment.

Detection and application of hypochlorous acid in both aqueous environments and living organisms.

The scarcity of water resources has raised concerns regarding drinking water safety. Excessive addition of hypochlorous acid (OCl-) as a disinfectant in drinking water can result in severe consequences. Moreover, abnormal levels of OCl- within the human body can lead to various diseases. Employing fluorescence analysis, the design and synthesis of specific fluorescent probes for simultaneous detection of OCl- in water environments and living organisms holds strategic significance in ensuring the safety of drinking water and mitigating potential risks caused by its abnormal concentrations. This article utilizes naphthalimide as a precursor to develop a novel probe enabling highly sensitive detection of OCl- in water environments and at the organelle level within living organisms. This endeavor serves to provide assurance for drinking water safety and offers health alerts.

Automatic planning for head and neck seed implant brachytherapy based on deep convolutional neural network dose engine.

BACKGROUND: Seed implant brachytherapy (SIBT) is an effective treatment modality for head and neck (H&N) cancers; however, current clinical planning requires manual setting of needle paths and utilizes inaccurate dose calculation algorithms. PURPOSE: This study aims to develop an accurate and efficient deep convolutional neural network dose engine (DCNN-DE) and an automatic SIBT planning method for H&N SIBT. METHODS: A cohort of 25 H&N patients who received SIBT was utilized to develop and validate the methods. The DCNN-DE was developed based on 3D-unet model. It takes single seed dose distribution from a modified TG-43 method, the CT image and a novel inter-seed shadow map (ISSM) as inputs, and predicts the dose map of accuracy close to the one from Monte Carlo simulations (MCS). The ISSM was proposed to better handle inter-seed attenuation. The accuracy and efficacy of the DCNN-DE were validated by comparing with other methods taking MCS dose as reference. For SIBT planning, a novel strategy inspired by clinical practice was proposed to automatically generate parallel or non-parallel potential needle paths that avoid puncturing bone and critical organs. A heuristic-based optimization method was developed to optimize the seed positions to meet clinical prescription requirements. The proposed planning method was validated by re-planning the 25 cases and comparing with clinical plans. RESULTS: The absolute percentage error in the TG-43 calculation for CTV V100 and D90 was reduced from 5.4% and 13.2% to 0.4% and 1.1% with DCNN-DE, an accuracy improvement of 93% and 92%, respectively. The proposed planning method could automatically obtain a plan in 2.5 ± 1.5 min. The generated plans were judged clinically acceptable with dose distribution comparable with those of the clinical plans. CONCLUSIONS: The proposed method can generate clinically acceptable plans quickly with high accuracy in dose evaluation, and thus has a high potential for clinical use in SIBT.

Phospholipase PLCE1 Promotes Transcription and Phosphorylation of MCM7 to Drive Tumor Progression in Esophageal Cancer.

Phospholipase C epsilon 1 (PLCE1) is a well-established susceptibility gene for esophageal squamous cell carcinoma (ESCC). Identification of the underlying mechanism(s) regulated by PLCE1 could lead to a better understanding of ESCC tumorigenesis. In this study, we found that PLCE1 enhances tumor progression by regulating the replicative helicase MCM7 via two pathways. PLCE1 activated PKCα-mediated phosphorylation of E2F1, which led to the transcriptional activation of MCM7 and miR-106b-5p. The increased expression of miR-106b-5p, located in intron 13 of MCM7, suppressed autophagy and apoptosis by targeting Beclin-1 and RBL2, respectively. Moreover, MCM7 cooperated with the miR-106b-25 cluster to promote PLCE1-dependent cell-cycle progression both in vivo and in vitro. In addition, PLCE1 potentiated the phosphorylation of MCM7 at six threonine residues by the atypical kinase RIOK2, which promoted MCM complex assembly, chromatin loading, and cell-cycle progression. Inhibition of PLCE1 or RIOK2 hampered MCM7-mediated DNA replication, resulting in G1-S arrest. Furthermore, MCM7 overexpression in ESCC correlated with poor patient survival. Overall, these findings provide insights into the role of PLCE1 as an oncogenic regulator, a promising prognostic biomarker, and a potential therapeutic target in ESCC. SIGNIFICANCE: PLCE1 promotes tumor progression in ESCC by activating PKCα-mediated phosphorylation of E2F1 to upregulate MCM7 and miR-106b-5p expression and by potentiating MCM7 phosphorylation by RIOK2.

Safety and efficacy of CT-guided radioactive iodine-125 seed implantation as a salvage treatment for recurrent head and neck cancer after two or more courses of radiotherapy.

BACKGROUND: In the past, patients with recurrent head and neck cancer (rHNC) who had previously received a high dose of radiation and were unable to undergo surgery were mainly treated with palliative chemotherapy due to the high incidence of side effects from re-irradiation. With the development of radiotherapy technology, re-irradiation of recurrent lesions by radioactive iodine-125 seed implantation (RISI) has been proposed as a feasible therapeutic approach. This study aimed to investigate the safety and efficacy of computed tomography (CT)-guided RISI in the treatment of rHNC after two or more courses of radiotherapy, and to analyze the prognostic factors. METHODS: Data of 33 patients with rHNC who received CT-guided RISI after two or more courses of radiotherapy were collected and statistically analyzed. The median cumulative dose of the previous radiotherapy was 110 Gy. Short-term efficacy was assessed by Response Evaluation Criteria in Solid Tumors (version 1.1) criteria, while adverse events were evaluated by Common Terminology Criteria for Adverse Events (version 5.0) criteria. RESULTS: The median gross tumor volume (GTV) was 29.5 cc, and the postoperative median dose to 90% of target volume (D90) was 136.8 Gy. For adverse reactions, enhanced pain was found in 3 (9.1%) patients, followed by grade 1 to 2 acute skin reactions in 3 (9.1%) patients, grade 2 to 3 late skin reactions in 2 (6.1%) patients, grade 1 to 2 early mucosal reactions in 4 (12.1%) patients, and mandibular osteonecrosis in 1 (3.0%) patient. Regarding the treatment efficacy, the 1- and 2-year local control (LC) rates were 47.8% and 36.4% (median LC time, 10 months), and the 1- and 2-year overall survival (OS) rates were 41.3% and 32.2% (median OS time, 8 months). The absence of adverse events was associated with better LC. CONCLUSIONS: CT-guided RISI, as a salvage therapy, demonstrated acceptable safety and efficacy in the treatment of rHNC after two or more courses of radiotherapy. TRIAL REGISTRATION: This study was registered at Chinese Clinical Trial Register database (Registration No. ChiCTR2200063261 ) in September 2, 2022.

Metal-free auxiliary pyrophosphate detection based on near-infrared carbon dots.

The excessive use of pyrophosphate (PPi) anions as additives poses a serious threat to human health and the environment. Considering the current status of PPi probes, the development of metal-free auxiliary PPi probes has important applications. In this study, a novel near-infrared nitrogen and sulfur co-doped carbon dots (N,S-CDs) were prepared. The average particle size of N,S-CDs was 2.25 ± 0.32 nm with average height was 3.05 nm. The probe N,S-CDs showed a special response to PPi, and a good linear relationship was obtained with PPi concentrations ranging from 0 to 1 µM, with the limit of detection being 0.22 nM. Tap water and milk were used for practical inspection, and ideal experimental results were acquired. In addition, the probe N,S-CDs also showed good results in biological systems, such as cell and zebrafish experiments.

Construction and Application of Multipurpose metal-organic frameworks -based Hydrogen Sulfide Probe.

Hydrogen sulfide (H2S) is a toxic gas derived from the sulfur industry and trace H2S in the environment can cause serious ecological damage while inhalation can cause serious damage and lead to disease. Therefore, the real-time and accurate detection of trace sulfur ions is of great significance for environmental protection and early disease detection. Considering the shortcoming of current H2S probes in terms of stability and sensitivity, the development of novel probes is necessary. Herein, a novel metal-organic frameworks (MOF)-based material, UiO-66-NH2@BDC, was designed and prepared for the visual detection of H2S with rapid response (< 6 s) and low detection limit of S2- (0.13 µM) by hydrogen bonding. Based on its good optical performance, the UiO-66-NH2@BDC probe can detect S2- in various water environments. More importantly, UiO-66-NH2@BDC probe realize imaging S2- in cells and live zebrafish.

Multi-scene visual hydrazine hydrate detection based on a dibenzothiazole derivative.

Hydrazine (N2H4) produced by industries is distributed into different environments, and seriously threatens ecology and human security. Hence, it is important to develop probes that detect N2H4 in various environments. In this study, a novel N2H4 fluorescent probe was prepared based on a dibenzothiazole derivative (DBTD). The obtained DBTD probe demonstrated a strong ratio of colorimetric detection of N2H4, a rapid response, and good selectivity and sensitivity (detection limit 0.438 µM). Based on its good performance, the DBTD probe was successfully applied for the determination of trace N2H4 in water, cells, and zebrafish. In addition, the results of the fluorescence colocalization experiment demonstrated the lysosomal-targetable ability of DBTD.

Stereotactic ablative brachytherapy with or without assistance of 3D-printing templates for inoperable locally recurrent or oligometastatic soft-tissue sarcoma: a multicenter real-world study.

The management of inoperable locally recurrent or oligometastatic soft-tissue sarcoma (STS) remains a clinical challenge. This study aimed to explore the long-term outcomes of stereotactic ablative brachytherapy (SABT) for these patients. Patients diagnosed with inoperable locally recurrent or oligometastatic STS from eight hospitals between 2006 and 2021 underwent iodine-125 (I-125) seed SABT, either with or without the assistance of three-dimensional (3D)-printing templates. The analysis concentrated on several key parameters, including objective response rate (ORR), disease control rate (DCR), local control time (LCT), overall survival (OS), adverse events (AEs), pain relief rate, and performance improvement rate. The ORR and DCR reached 78.3% and 95.0%, respectively. The results of multivariate logistic regression analysis indicated that a smaller tumor volume and a higher treatment dose were significantly associated with complete response (P < 0.001; P=0.036). The 1-, 3-, and 5-year LCT rates were 73.2%, 40.6%, and 37.9%, respectively. The 1-, 3-, and 5-year OS rates reached 83.1%, 50.5%, and 36.1%, respectively. Multivariate analysis revealed that a higher dose, a smaller tumor volume, and utilization of 3D-printing templates were significantly positive prognostic factors of LCT (P=0.006; P=0.007; P=0.034). Moreover, the tumor locations of trunk wall and extremities and lower tumor grade (G1/2) were significantly positive prognostic factors of survival (P=0.008; P=0.002). Pain relief rate was 88.0%, and the performance improvement rate was 46.7%. The AEs were predominantly of grade ≤ 2 and were well-tolerated. SABT seems to be an efficacious and safe alternative therapy for inoperable locally recurrent or oligometastatic STS.

Current radiotherapy for recurrent head and neck cancer in the modern era: a state-of-the-art review.

BACKGROUND: In the management of head and neck cancer (HNC) patients, local recurrence is a common cause of treatment failure. Only a few patients with recurrent HNC (rHNC) are eligible for salvage surgery and the majority of patients receive systemic therapy and radiotherapy. In recent years, with the development of irradiation technology, radiotherapy for rHNC patients has markedly attracted clinicians' attention and its therapeutic effects on patients with end-stage cancer are worthy of investigation as well. METHODS: Several studies have investigated the role of radiotherapy in the treatment of rHNC patients. We reviewed retrospective reports and prospective trials published in recent decades that concentrated on the management of rHNC. RESULTS: A growing body of evidence supported the application of irradiation to rHNC patients. According to the results of this review, current radiotherapy could achieve a better efficacy with a lower incidence of toxicity. CONCLUSION: Radiotherapy is a promising treatment for rHNC patients.

A comparative study of dosimetric parameters of 3D-printed non-coplanar template-assisted CT-guided iodine-125 seed implantation brachytherapy in patients with inguinal lymph node metastatic carcinomas.

Purpose: To compare the pre-plan and post-plan dosimetric parameter differences of 3D-printed non-coplanar templates (3D-PNCT)-assisted computed tomography (CT)-guided iodine-125 (125I) radioactive seed implantation brachytherapy (RISI) in patients with inguinal lymph node metastasis (ILNM). Material and methods: This was a retrospective study of 15 patients with ILNM carcinomas treated with 3D-PNCT-assisted CT-guided RISI between May, 2015 and April, 2018. All patients underwent prior external beam radiotherapy (EBRT) or surgery. Dosimetric parameters included D90, D100 (dose delivered to 90% and 100% of the volume, respectively), V100, V150, V200 (percentage of target volume receiving 100%, 150%, and 200% of the prescribed dose, respectively). Quality parameters included conformal index (CI), external index (EI), and homogeneity index (HI). Paired t-test and Bland-Altman analysis were applied to compared pre-plan and post-plan parameters. Results: The median gross tumor volume (GTV) in the pre-plan was 8.7 ml (range, 0.8-185.1 ml). There were statistically significant differences in V100, V150, CI, and EI (p < 0.05). Bland-Altman analysis indicated that accidental error of RISI was small. In 1 of the 15 cases, D90 and D100 exceeded the prescribed therapeutic accuracy. In 1 of the 15 cases, V150, EI, and GTV were outside the specified accuracy range (95% confidence interval). Conclusions: 3D-PNCT-assisted CT-guided RISI is a safe, accurate, and feasible choice in ILNM treatment. The procedure of RISI has significantly improved. The pre-plan can be accurately executed by 3D-PNCT-assisted CT-guided RISI.

Novel pyroptosis-associated genes signature for predicting the prognosis of sarcoma and validation.

BACKGROUND: Sarcoma is a rare mesenchymal malignant tumor. Recently, pyroptosis has been reported to be a mode of programmed cell death. Nonetheless, levels of pyroptosis-associated genes in sarcoma and its relevance to prognostic outcomes are yet to be elucidated. RESULTS: Sarcoma cases were classified into two subtypes with regards to differentially expressed genes. We established a profile composed of seven genes and classified the sarcoma patients into low- and high-risk groups through least absolute shrinkage and selection operator Cox regression. Survival rate of low-risk sarcoma patients was markedly higher, relative to high-risk group (P<0.001). In combination with clinical features, the risk score was established to be an independent predictive factor for OS of sarcoma patients. Chemotherapeutic drug sensitivity response analysis found 65 drugs with higher drug sensitivity in low-risk, than in high-risk group and 14 drugs with higher drug sensitivity in the high-risk patient group, compared with low-risk patient group. In addition, functional enrichment, pathway and gene mutation of the two modules were analyzed. Finally, we used qRT-PCR to detect the expression of seven pyroptosis-related genes in tumor cells, and human skeletal muscle cells, compared with human skeletal muscle cells, PODXL2, LRRC17, GABRA3, SCUBE3 and RFLNB genes show high expression levels in tumor cells, while IGHG2 and hepatic leukemia factor show low expression levels in tumor cells. CONCLUSIONS: Our research suggest that pyroptosis is closely associated with sarcoma, and these findings confirm that pyroptosis-associated seven genes have a critical role in sarcoma and are potential prognostic factors for sarcoma.

Preparation of novel fluorescent probe based on carbon dots for sensing and imaging Fe(III) and pyrophosphate in cells and zebrafish.

Ferric ions (Fe3+) and pyrophosphate anions (PPi) are involved in many physiological processes and play important roles in biological systems. The abnormal level of Fe3+ and PPi will cause serious damage to the environment and life. At present, the application of such probes in life, especially in vivo, is still very scarce. So, the development of a fluorescent probe to simultaneously detect Fe3+ and PPi has great significance to the health of the environment and organisms. Herein, nitrogen-doped carbon quantum dots (N-CDs) were synthesized via solvothermal treatment, using biuret and citric acid as precursors. The synthesized N-CDs showed highly selective and sensitive detection of Fe3+ through a photoluminescence quenching effect. The fluorescence of N-CDs quenched by Fe3+ could be restored with PPi, rendering the N-CDs/Fe3+ sensor promising for PPi detection ('OFF-ON'). The linear ranges of detection for Fe3+ and PPi were 3-30 and 2-12 µM, and the limits of detection were 2.71 and 1.12 µM, respectively. The practical applications of N-CDs were tested using tap water samples. Furthermore, N-CDs can be used for the detection and imaging of Fe3+ and PPi in HeLa cells and zebrafish owing to their excellent optical properties.

Re-Irradiation for Recurrent Cervical Cancer: A State-of-the-Art Review.

The recurrence rate of cervical cancer after primary treatment can reach 60%, and a poor prognosis is reported in most cases. Treatment options for the recurrence of cervical cancer mainly depend on the prior treatment regimen and the location of recurrent lesions. Re-irradiation is still considered as a clinical challenge, owing to a high incidence of toxicity, especially in in-field recurrence within a short period of time. Recent advances in radiotherapy have preliminarily revealed encouraging outcomes of re-irradiation. Several centers have concentrasted on stereotactic body radiation therapy (SBRT) for the treatment of well-selected cases. Meanwhile, as the image-guiding techniques become more precise, a better dose profile can also be achieved in brachytherapy, including high-dose-rate interstitial brachytherapy (HDR-ISBT) and permanent radioactive seed implantation (PRSI). These treatment modalities have shown promising efficacy with a tolerable toxicity, providing further treatment options for recurrent cervical cancer. However, it is highly unlikely to draw a definite conclusion from all of those studies due to the large heterogeneity among them and the lack of large-scale prospective studies. This study mainly reviews and summarizes the progress of re-irradiation for recurrent cervical cancer in recent years, in order to provide potential treatment regimens for the management of re-irradiation.

Environmental Justice in Greater Los Angeles: Impacts of Spatial and Ethnic Factors on Residents' Socioeconomic and Health Status.

Environmental justice advocates that all people are protected from disproportionate impacts of environmental hazards. Despite this ideal aspiration, social and environmental inequalities exist throughout greater Los Angeles. Previous research has identified and mapped pollutant levels, demographic information, and the population's socioeconomic status and health issues. Nevertheless, the complex interrelationships between these factors remain unclear. To close this knowledge gap, we first measured the spatial centrality using sDNA software. These data were then integrated with other socioeconomic and health data collected from CalEnvironScreen, with census tract as the unit of analysis. Finally, structural equation modeling (SEM) was executed to explore direct, indirect, and total effects among variables. The results show that the White population tends to reside in the more segregated areas and lives closer to green space, contributing to higher housing stability, financial security, and more education attainment. In contrast, people of color, especially Latinx, experience the opposite of the environmental benefits. Spatial centrality exhibits a significant indirect effect on environmental justice by influencing ethnicity composition and pollution levels. Moreover, green space accessibility significantly influences environmental justice via pollution. These findings can assist decision-makers to create a more inclusive society and curtail social segregation for all individuals.

Dosimetric Evaluation and Clinical Application of Radioactive Iodine-125 Brachytherapy Stent in the Treatment of Malignant Esophageal Obstruction.

Objective: To evaluate the dosimetric characteristics and the clinical application of radioactive iodine-125 brachytherapy stent (RIBS) in malignant esophageal obstruction. Methods: The dose distribution of RIBS with different seed spacing, diameter and length was studied by treatment planning system (TPS) calculation, thermoluminescence dosimeter (TLD) measurement and Monte Carlo (MC) data fitting. And the data of esophageal cancer patients who were treat with this type of RIBS was analyzed retrospectively. Results: Doses around the RIBS calculated by the TPS lay between those measured by the TLDs and those simulated by the MC, and the differences between the three methods were significant (p<0.05), the overall absolute dose differences among the three methods were small. Dose coverage at 1.5 cm from the center was comprehensive when the activity reached 0.6 mCi. Both the conformability and the uniformity of isodose lines produced by a seed spacing of 1.0 cm were superior to those produced by a seed spacing of 1.5 cm. The data of 50 patients treated with RIBS was analyzed. They were followed up until February 2020 when all of the patients died. The overall improvement rate of dysphagia after RIBS implant was 90%. Moderate and severe complications with an incidence of more than 10% were hematemesis (28%), pain (20%), and lung infection (10%). Stent restenosis occurred in 4 patients at a median interval of 108 days from the procedure. The overall incidence of fatal complications was 38% (including hematemesis, infection and asphyxia). The median survival time of patients with and without a history of radiotherapy were 3.4 months and 6 months, respectively, the difference of which was significant (p=0.021). No other factors affecting survival were identified. For patients with and without a history of radiotherapy, the incidences of fatal complications were 51.7% and 19%, respectively (p=0.019). No correlation between dose and stent restenosis was found. Conclusion: TPS calculations are suitable for clinical applications. RIBS can effectively alleviate obstructive symptoms for patients with malignant esophageal obstruction, but the incidence of fatal complications was high, care should be taken when choosing this treatment.

Lysosome-targeting benzothiazole-based fluorescent probe for imaging viscosity and hypochlorite levels in living cells and zebrafish.

Viscosity and hypochlorite (OCl-) play an important role in biological activities and may cause negative effects at abnormal levels. In this study, a novel lysosome-target fluorescent probe BDHA was obtained based on a benzothiazole derivative. Probe BDHA showed linear ranges of detection for viscosity from 1.62 cP to 851.6 cP with a fluorescent turn-on response. It can also be used as a sensor for OCl- with a turn-off response and showed a good linear range from 0 to 390 µM, with the detection limit calculated to be 2.8 µM. Moreover, BDHA can also be used to image viscosity and OCl- levels in HeLa cells and zebrafish, owing to its excellent optical properties.

A review on permanent implants for prostate brachytherapy with comparison between stranded and loose seeds.

A systematic literature review to validate the conclusions with regard to stranded seeds versus loose seeds. Published data for this review were identified by searching the PubMed databases. PD90, PV100, PV150, UD30, and RV100 acquired during the perioperative period and the postoperative period were analyzed by meta-analysis. Based on these studies, in addition to the reduction of migration and displacement, stranded seeds had some dosimetric advantages, especially in dose homogeneity and coverage of target area due to its connection characteristics. We also noticed implanted seeds usually excessive both in stranded seeds group and loose seed group. Intraoperatively built custom links will prolong operation time, with the proficiency of technology, the prolonged time gradually decreases.

PD-1 Inhibitor Maintenance Therapy Combined Iodine-125 Seed Implantation Successfully Salvage Recurrent Cervical Cancer after CCRT: A Case Report.

Cervical cancer is the fourth most common cancer in females worldwide. Patients with stage III and IV cervical cancer based on the Federation of Gynecology and Obstetrics (FIGO) classification have higher recurrence rates. Because of organs at risk (OAR) protection and the low indication rate of salvage surgery, the choice of treatment is always challenging. Systemic chemotherapy is palliative and can be performed in conjunction with surgery or radiotherapy; however, it has no significant benefit to survival. Brachytherapy and stereotactic body radiotherapy (SBRT) are characterized by extremely high radiation doses applied to tumor cells while sparing the normal tissues. Several studies have investigated the efficacy of these technologies in recurrent cervical cancer and showed promising results. The immune checkpoint inhibitors approach was also investigated and showed promising results too. Herein, we report a case of a patient with cervical cancer that recurred five months after adjuvant chemotherapy and concurrent chemoradiotherapy. The disease prognosis after interstitial implantation brachytherapy (IIB) was determined. Then, the patient underwent radioactive 125I-seed implantation combined with PD-1 inhibitor treatment. The patient exhibited a partial response after seed implantation, and up to now, the duration of this partial response was 24 months.

Distinct Genetic Structure Reflects Ploidy Level Differentiation in Newly Discovered, Extremely Small Populations of Xanthocyparis vietnamensis from Southwestern China.

Population genetic assessment is crucial for the conservation and management of threatened species. Xanthocyparis vietnamensis is an endangered species that is currently restricted to karst mountains in southwestern China and Vietnam. This rare conifer was first recorded in 2002 from northern Vietnam and then in 2013 from Guangxi, China, yet nothing is known about its genetic diversity nor ploidy level variation, although previous cytological study suggest that Vietnamese populations are tetraploids. There have been about 45 individuals found to date in Guangxi, China. Here, we genotyped 33 X. vietnamensis individuals using 20 newly developed, polymorphic microsatellite loci, to assess the genetic variability of its extremely small populations. The genetic diversity of X. vietnamensis (H E = 0.511) was lower than that of two other heliophile species, Calocedrus macrolepis and Fokienia hodginsii, which have similar distribution ranges. This is consistent with the signature of a genetic bottleneck detected in X. vietnamensis. Although the population genetic differentiation coefficient across loci is moderate (F ST = 0.125), STRUCTURE analysis revealed two distinct genetic clusters, namely the northern and southern population groups; DAPC analysis grouped the southern populations together in one cluster separate from the northern populations; AMOVA analysis detected a significant genetic differentiation between the two population groups (F RT = 0.089, p < 0.05), and BARRIER analysis detected a genetic barrier between them. Moreover, we detected differentiation in ploidy level between northern and southern populations, sampled individuals from the former and the later are all diploid and tetraploid cytotypes with mean genome sizes of 26.08 and 48.02 pg/2C, respectively. We deduced that heterogeneous geomorphology and historical events (e.g., human deforestation, Quaternary climate oscillations) may have contributed to population fragmentation and small population size in X. vietnamensis. Considering both genetic and ploidy level differentiation, we propose that two different management units (northern and southern) should be considered and a combination of in situ and ex situ conservation measures should be employed to preserve populations of this endangered species in southwestern China in the light of our findings.