A pretreatment multiparametric MRI-based radiomics-clinical machine learning model for predicting radiation-induced temporal lobe injury in patients with nasopharyngeal carcinoma

BACKGROUND

To establish and validate a machine learning model using pretreatment multiparametric magnetic resonance imaging-based radiomics data with clinical data to predict radiation-induced temporal lobe injury (RTLI) in patients with nasopharyngeal carcinoma (NPC) after intensity-modulated radiotherapy (IMRT).

METHODS

Data from 230 patients with NPC who received IMRT (130 with RTLI and 130 without) were randomly divided into the training (n = 161) and validation cohort (n = 69) with a ratio of 7:3. Radiomics features were extracted from pretreatment apparent diffusion coefficient (ADC) map, T2-weighted imaging (T2WI), and CE-T1-weighted imaging (CE-T1WI). T-test, spearman rank correlation, and least absolute shrinkage and selection operator (LASSO) algorithm were employed to identify significant radiomics features. Clinical features were selected with univariate and multivariate analyses. Radiomics and clinical models were constructed using multiple machine learning classifiers, and a clinical-radiomics nomogram that combined clinical with radiomics features was developed. Receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA) were drawn to compare and verify the predictive performances of the clinical model, radiomics model, and clinical-radiomics nomogram.

RESULTS

A total of 5064 radiomics features were extracted, from which 52 radiomics features were selected to construct the radiomics signature. The AUC of the radiomics signature based on multiparametric MRI was 0.980 in the training cohort and 0.969 in the validation cohort, outperforming the radiomics signature only based on T2WI and CE-T1WI (p < 0.05), which highlighted the significance of the DWI sequence in the prediction of temporal lobe injury. The area under the curve (AUC) of the clinical model was 0.895 in the training cohort and 0.905 in the validation cohort. The nomogram, which integrated radiomics and clinical features, demonstrated an impressive AUC value of 0.984 in the validation set; however, no statistically significant difference was observed compared to the radiomics model. The calibration curve and decision curve analysis of the nomogram demonstrated excellent predictive performance and clinical feasibility.

CONCLUSIONS

The clinical-radiomics nomogram, integrating clinical features with radiomics features derived from pretreatment multiparametric MRI, exhibits compelling predictive performance for RTLI in patients diagnosed with NPC.

Flexible ureteroscopy in Chinese air force pilots with renal calculi: a cohort study at a single medical centre

INTRODUCTION

Renal calculi are the predominant urological ailment in air force pilots. Flexible ureteroscopy (FURS) constitutes a valuable approach for renal calculi treatment. This study presents a decade-long exploration of using FURS for renal calculi treatment in air force pilots. Additionally, it investigates the safety and feasibility of granting waiver flights to pilots with renal parenchyma calcification.

METHODS

From December 2009 to December 2019, a retrospective review was conducted on Chinese air force pilots undergoing treatment for renal calculi. Among the pilots assessed, a total of 71 individuals underwent FURS. Endoscopic methodology involved the insertion of a flexible ureteroscope into the ureter and renal pelvis, guided by a safety wire. Stone fragmentation was achieved using a holmium laser fibre, followed by extraction using a soft stone basket. Postoperative non-enhanced CT (NECT) scans was used to confirm stone clearance. Furthermore, clinical diagnoses were classified based on endoscopic findings and postoperative NECT results. All data were presented as mean (SD) or median (minimum-maximum) for continuous variables and frequency counts and percentages for categorical variables.

RESULTS

FURS identified free kidney stones in 60 cases among all patients. The remaining 11 cases, without free stones detected during ureteroscopy, exhibited persistent high-density spots on postoperative NECT. Of the 60 cases with stones, renal calculi were successfully cleared in 30 pilots, while the remaining 30 exhibited persistent high-density spots on NECT postsurgery. Pilots with completely cleared free stones were deemed fit for flight. Pilots with diagnosed renal parenchyma calcification were granted permission to fly under waivers following a meticulous evaluation.

CONCLUSIONS

FURS could not only effectively eliminate renal calculi but also accurately diagnose renal parenchyma calcification, facilitating a prompt return to flight for pilots. A protocol for managing pilot renal calculi, informed by FURS and our experience, is proposed.

A Novel Mechanism of MSCs Responding to Occlusal Force for Bone Homeostasis

Alveolar bone, as tooth-supporting bone for mastication, is sensitive to occlusal force. However, the mechanism of alveolar bone loss after losing occlusal force remains unclear. Here, we performed single-cell RNA sequencing of nonhematopoietic (CD45-) cells in mouse alveolar bone after removing the occlusal force. Mesenchymal stromal cells (MSCs) and endothelial cell (EC) subsets were significantly decreased in frequency, as confirmed by immunofluorescence and flow cytometry. The osteogenic and proangiogenic abilities of MSCs were impaired, and the expression of mechanotransducers yes associated protein 1 (Yap) and WW domain containing transcription regulator 1 (Taz) in MSCs decreased. Conditional deletion of Yap and Taz from LepR+ cells, which are enriched in MSCs that are important for adult bone homeostasis, significantly decreased alveolar bone mass and resisted any further changes in bone mass induced by occlusal force changes. Interestingly, LepR-Cre; Yapf/f; Tazf/f mice showed a decrease in CD31hi endomucin (Emcn)hi endothelium, and the expression of some EC-derived signals acting on osteoblastic cells was inhibited in alveolar bone. Mechanistically, conditional deletion of Yap and Taz in LepR+ cells inhibited the secretion of pleiotrophin (Ptn), which impaired the proangiogenic capacity of LepR+ cells. Knockdown in MSC-derived Ptn repressed human umbilical vein EC tube formation in vitro. More important, administration of recombinant PTN locally recovered the frequency of CD31hiEmcnhi endothelium and rescued the low bone mass phenotype of LepR-Cre; Yapf/f; Tazf/f mice. Taken together, these findings suggest that occlusal force governs MSC-regulated endothelium to maintain alveolar bone homeostasis through the Yap/Taz/Ptn axis, providing a reference for further understanding of the relationship between dysfunction and bone homeostasis.

[Clinical and electrophysiological characteristics and treatment outcomes of anti-neutrophil cytoplasmic antibody ANCA-associated vasculitic neuropathy]

Objective: To investigate the clinical and electrophysiological characteristics of ANCA-associated vasculitic neuropathy (VN) and analyze the predictors of treatment outcomes. Methods: Retrospective case series. In all, 652 consecutive patients with ANCA-associated vasculitis were admitted to the First Medical Center of the Chinese PLA General Hospital between January 2006 and December 2022. Peripheral neuropathy occurred in 91 patients. Patients were excluded if other known causes of neuropathy were present. Sixty-one patients were eventually enrolled, including 17 with eosinophilic granulomatosis with polyangiitis (EGPA), 11 with granulomatosis polyangiitis (GPA), and 33 with microscopic polyangiitis (MPA). Their clinical data were collected and clinical characteristics, VN manifestations, electrophysiological findings (including interside amplitude ratio [IAR]), and treatment outcomes were compared among the three subsets of AAV. Then, factors influencing the treatment outcomes were analyzed using multivariable logistic regression analysis. Results: Peripheral neuropathy occurred in 62.1%(18/29) of EGPA, 8.3%(15/180) of GPA, and 13.1%(58/443) of MPA patients. The age at onset and examination was higher in patients with MPA than those with EGPA or GPA (P<0.01). The occurrence of VN was later in patients with GPA than those with EGPA (P<0.01), and the GPA group had fewer affected nerves than the other two groups (P<0.016). The abnormal IARs of motor nerves in lower limbs were more detected in the EGPA than the MPA group (P<0.01). Logistic regression analysis suggested that higher Birmingham vasculitis activity score-version 3 (BVAS-V3) (OR=6.85, 95%CI 1.33-35.30) was associated with better treatment outcomes of VN. However, central nervous system involvement was a risk factor for poor treatment outcomes (OR=0.13, 95%CI 0.02-0.89). Conclusions: The clinical and electrophysiological characteristics of VN were slightly different among subsets of AAV. Patients with GPA often presented with polyneuropathy and had fewer nerves affected; mononeuritis multiplex was more common in EGPA than GPA and MPA. Higher BVAS-V3 and central nervous system involvement might predict the treatment outcome of VN.

Targeted long-read sequencing for comprehensive detection of CYP21A2 mutations in patients with 21-hydroxylase deficiency

BACKGROUND

21-Hydroxylase deficiency (21-OHD) is caused by pathogenic CYP21A2 variations. CYP21A2 is arranged in tandem with its highly homologous pseudogene CYP21A1P; therefore, it is prone to mismatch and rearrangement, producing different types of complex variations. There were few reports on using only one method to detect different CYP21A2 variants simultaneously.

AIMS

Targeted long-read sequencing method was used to detect all types of CYP21A2 variants in a series of patients with 21-OHD.

METHODS

A total of 59 patients with 21-OHD were enrolled from Peking Union Medical College Hospital. Long-range locus-specific PCR and long-read sequencing (LRS) were performed to detect the pathogenic variants in CYP21A2.

RESULTS

Copy-number variants of CYP21A2 were found in 25.4% of patients, including 5.1% with 3 copies of CYP21A2, 16.9% with 1 copy of CYP21A2, and 3.4% with 0 copy of CYP21A2. The remaining 74.6% of patients had 2 copies of CYP21A2. Pathogenic variants were identified in all 121 alleles of 59 patients. Specifically, single-nucleotide variants and small insertions/deletions (< 50 bp) were detected in 79 alleles, of which conversed from CYP21A1P were detected in 63 alleles, and rare variants were found in the other 16 alleles. Large gene conversions (> 50 bp) from pseudogene were detected in 10 alleles, and different chimeric genes (CYP21A1P/CYP21A2 or TNXA/TNXB) formed by large deletions were detected in 32 alleles. Of all variants, p.I173N was the most common variant (19.0%).

CONCLUSIONS

Our study demonstrated that targeted long-read sequencing is a comprehensive method for detecting CYP21A2 variations, which is helpful for genetic diagnosis in 21-OHD patients.

Risk factors for portal vein system thrombosis after partial splenic embolisation in cirrhotic patients with hypersplenism

AIM

To determine risk factors for portal venous system thrombosis (PVST) after partial splenic artery embolisation (PSAE) in cirrhotic patients with hypersplenism.

MATERIALS AND METHODS

Between March 2014 and February 2022, 428 cirrhotic patients with hypersplenism underwent partial splenic artery embolisation and from these patients 208 were enrolled and 220 were excluded. Medical records of enrolled patients were collected. Computed tomography (CT) images were reviewed by two blinded, independent radiologists. Statistical analyses were performed by using SPSS.

RESULTS

Progressive PVST was observed in 18.75% (39/208) of cirrhotic patients after PSAE. No significant differences in peripheral blood counts, liver function biomarkers, and renal function were observed between the patients with progressive PVST and the patients without progressive PVST. The imaging data showed significant differences in PVST, the diameters of the portal, splenic, and superior mesenteric veins between the progressive PVST group and non-progressive PVST group. Univariate and multivariate analysis demonstrated portal vein thrombosis, spleen infarction percentage, and the diameter of the splenic vein were independent risk factors for progressive PVST. Seventeen of 173 (9.83%) patients showed new PVST; the growth of PVST was observed in 62.86% (22/35) of the patients with pre-existing PVST. Spleen infarction percentage and the diameter of the splenic vein were independent risk factors for new PVST after PSAE.

CONCLUSION

The present study demonstrated portal vein thrombosis, spleen infarction percentage, and the diameter of the splenic vein were independent risk factors for PVST after PSAE in cirrhotic patients with hypersplenism.

Bridging the Gap of Radiotherapy Treatment Planning Quality between High-Income, and Low- and Middle-Income Countries Using Knowledge-Based Planning

PURPOSE/OBJECTIVE(S)

Radiotherapy departments in low- and middle-income countries (LMICs) like Guatemala have recently introduced intensity-modulated radiotherapy (IMRT). IMRT has become the standard of care in high-income countries (HIC) due to reduced toxicity and improved outcomes in some cancers. The purpose of this work is to show the feasibility of adapting knowledge-based (KB) models established in a HIC to a LMIC lacking experience in IMRT to improve plan quality and planning efficiency.

MATERIALS/METHODS

A Halcyon Linac was installed at our clinic in Guatemala in 2019 and has been used to treat approximately 90 patients daily with IMRT. A model developed on a cohort of head and neck cancer patients at a US academic radiotherapy center were applied at our center to create 20head and neck VMAT plans with different prescriptions, including simultaneous-integrated and sequential boosts.

RESULTS

The plans created using the KB models achieved similar coverage of the planning target volume for each plan KB plans showed better 1) Parotid sparing with a mean dose reduction between 5%-25% and spinal cord maximum dose reduction between 3%-15%. The time efficiency to create VMAT plans using KB model versus manual planning improved four-fold, on average one hour versus more than 4 hours, respectively.

CONCLUSION

Despite different prescriptions, guidelines and demographics of cancer patients between two institutions in a HIC and LMIC, this work demonstrates that KB planning can be used to generate better and more consistent VMAT plans versus manually created plans. In addition, KB planning has the potential to greatly increase planning efficiency higher efficiency and help address the shortage of medical physicists and dosimetrists in LMICs.

Dissecting Systemic T Cell Responses after Stereotactic Ablative Radiotherapy in NSCLC by Single-Cell RNA and T Cell Receptor Sequencing

PURPOSE/OBJECTIVE(S)

There is accumulating evidence that stereotactic ablative radiotherapy (SABR) modulates immune responses to cancer; combining SABR and immunotherapy could promote the abscopal effect, but the precise effects of SABR on patients' systemic T cells is unclear. Here, we investigated SABR-induced systemic T cell response in early-stage non-small cell lung cancer (NSCLC) by single-cell RNA and T cell receptor sequencing.

MATERIALS/METHODS

We performed single-cell RNA and T cell receptor sequencing on 29,439 T cells from four pairs of peripheral blood before and after SABR in early-stage NSCLC patients. Cell clustering and dimensionality reduction, SingleR, feature genes score, and TCR profiling analyses were used to investigate the heterogeneity of T cells and their changes following SABR.

RESULTS

We identified fourteen T cell subtypes using unsupervised graph-based clustering of uniform manifold approximation and projection. By comparing the gene set scores of CD8_TE and CD8_EM pre- and post-SABR, we found both cytotoxic and inhibitory scores were significantly elevated in CD8_TE (both P < 0.001), while cytotoxic score was significantly increased in CD8_EM (P < 0.001) after SABR. We also found that CD4_TE showed increased cytotoxic scores and decreased Treg scores (P < 0.001 and < 0.05, respectively), while Treg cells showed decreased inhibitory and Treg scores (P < 0.001 and <0.01, respectively) after SABR. The proportion of large TCR clones was higher after SABR, which was accompanied by a decrease in proportion of single clones. When we compared the transcriptomes of CD8_TE cells between the single, small and large clones post-SABR, we found high expression of GZMB and KLRC3 in cells with large clones, and GZMK, IL7R, and SELL in small and single clones. This suggested that T cells after SABR with large clones may have higher cytotoxicity than those with small and single clones.

CONCLUSION

Our study identified systemic T cell activation after SABR at single-cell resolution, providing unprecedented insight into the immune-modulatory role of SABR in early-stage NSCLC.

Standardizing LT Chest Wall Radiotherapy Treatment Planning in a Low- or Middle- Income Country Radiotherapy Clinic Using Knowledge Based Planning

PURPOSE/OBJECTIVE(S)

Radiotherapy departments in low- or middle-income countries (LMICs) tend to lag behind introducing emerging technologies like intensity-modulated radiotherapy (IMRT). IMRT has become the standard of care in high-income countries (HIC) due to reduced toxicity and improved outcomes in a wide variety of cancers. The purpose of this work is showing the results of left Chest-Wall knowledge-based planning (KBP) standardization and implementation in a LMIC setting.

MATERIALS/METHODS

A Halcyon Linac was installed at our clinic in Guatemala in 2019 and currently used to treat ∼90 IMRT patients daily. The standardization of IMRT procedures has been difficult for complex sites like chest-wall. The steps for standardization included: AAPM TG-263 nomenclature implementation, and planning workflows within the TPS, creation of optimization structures, and plan quality evaluation following RTOG1005 protocol hypofractionation arm. 25 plans were created manually achieving all RTOG1005 protocol constraints. The statistics were analyzed trough the model analytics tool provided by KPB manufacturer.

RESULTS

The results show that more plans are needed to improve the KBP model. This initial model was used to create a standardized clinical protocol in the TPS in order to continue adding plans to the KBP model database. This approach ensures that we obtain consistent plan quality and standardize our planning. The manual planning objectives achieved: CONCLUSION: The experience using the TPS to standardize our treatment planning process achieved good consistency in our planning objectives. This approach will help create KBP models according to our own clinic-specific requirements. Future work will be made to compare our LMIC KBP models with those made at a HIC academic radiotherapy center.

Impact of AI-Based Auto-Segmentation on Radiotherapy Processes in Low and Middle-Income Countries

PURPOSE/OBJECTIVE(S)

Radiotherapy processes require significant human resources and expertise, creating a barrier for rapid deployment in low and middle-income countries (LMICs). Optimal radiotherapy (RT) relies on accurate segmentation of tumor targets and organs-at-risk (OARs) during the RT planning process. This study reports the impact of AI-based auto-segmentation on RT processes in an LMIC.

MATERIALS/METHODS

Ten patients including five head and neck (HN), and five prostate cancer patients were randomly selected. Their planning CT images were subjected to auto- segmentation using an FDA-approved AI software tool, and manual segmentation by an experienced radiation oncologist from a Sub-Saharan African RT clinic. The control data consisted of contours from an experienced radiation oncologist and dosimetrists at a large academic institution in the US. For prostate cases, the contours included the prostate, seminal vesicles, bladder, rectum, penile bulb, and both femoral heads. For HN cases, the contours included the brain, brainstem, bilateral eyes, lens, optic nerves, cochlea, parotids, optic chiasm, spinal cord, oral cavity, and mandible. The time to complete the segmentation was recorded for both auto-segmentation and manual contours from the LMIC. The DICE similarity coefficients were used for comparative evaluation.

RESULTS

The average time for contouring per patient was 2 minutes for AI compared to 57 minutes for manual contouring in the LMIC. When comparing the control data, AI pelvic contours provide a slightly better agreement than LMIC manual contours for all the OARs, with the following mean DICE coefficients for AI vs LMIC manual contours: bladder (0.971 vs 0.958), left femoral head (0.960 vs 0.949), right femoral head (0.959 vs 0.941), rectum (0.880 vs 0.867), prostate (0.836 vs 0.824), seminal vesicles (0.696 vs 0.580), and penile bulb (0.536 vs 0.528). For HN contours, AI provide a better agreement for 7 of 11 OARs than the LMIC manual contours, with the following mean DICE coefficients: brain (0.972 vs 0.982), mandible (0.877 vs 0.925), right parotid (0.847 vs 0.800), left parotid (0.798 vs 0.792), spinal cord (0.837 vs 0.821), left eye (0.875 vs 0.832), right eye (0.867 vs 0.836), brainstem (0.866 vs 852), oral cavity (0.796 vs 0.787), left lens (0.650 vs 0.729) and right lens (0.671 vs 0.682). Neither AI contours nor LMIC manual contours had good agreement with the control data (<0.600) for optic nerves, chiasm, and cochlea due to their small volumes.

CONCLUSION

AI-based auto-segmentation tools are capable of producing contours of comparable quality to those generated by manual segmentation for both pelvic and HN cancer patients in LMICs, while also resulting in substantial time savings. AI-based auto-segmentation holds tremendous potential for improving radiotherapy care in LMICs with limited sources.

[Evolution and progress of surgical intervention strategies for acute pancreatitis]

Acute pancreatitis is one of the common surgical acute abdominal diseases. Since people first recognized acute pancreatitis in the middle of the nineteenth century, a diversified minimally invasive treatment model with standardization has been formed today. According to the main line of surgical intervention of acute pancreatitis treatment,this period can be roughly divided into five stages:exploration stage, conservative treatment stage, pancreatectomy stage, debridement and drainage of the pancreatic necrotic tissue stage, and minimally invasive treatment as the first choice led by the multidisciplinary team mode stage. Throughout history, the evolution and progress of surgical intervention strategies for acute pancreatitis cannot be separated from the progress of science and technology, the update of treatment concepts and the further understanding of the pathogenesis. This article will summarize the surgical characteristics of acute pancreatitis treatment at each stage to explain the development of surgical treatment of acute pancreatitis,to help investigate the development of surgical treatment of acute pancreatitis in the future.

[Application of veno-arterio-venous extracorporeal membrane oxygenation in patients with critical respiratory failure combined with refractory shock]

Objective: To preliminarily analyze the application experience of veno-arterio-venous extracorporeal membrane oxygenation (VAV-ECMO).The VAV-ECMO is a rescue strategy for patients with extremely critical respiratory failure combined with refractory shock. Methods: From February 2016 to February 2022, the characteristics and outcomes of patients who were started on either veno-venous or veno-arterial ECMO due to respiratory or hemodynamic failure, and then converted to VAV-ECMO in respiratory intensive care unit (ICU) of Beijing Chaoyang Hospital were analyzed. Results: A total of 15 patients underwent VAV-ECMO, aged 53 (40, 65) years, and 11 of whom were male. Within the group, VV-ECMO was initially used in 12 patients due to respiratory failure, but then VAV-ECMO was used due to cardiogenic shock (7/12) and septic shock (4/12), while VAV-ECMO was established in two patients due to lung transplantation. One patient was diagnosed with pneumonia complicated by septic shock, which was initially determined to be VA-ECMO, but then switched to VAV-ECMO because it was difficult to maintain oxygenation. The time from the establishment of VV or VA-ECMO to the switch to VAV-ECMO was 3 (1, 5) days and the VAV-ECMO support time was 5 (2, 8) days. ECMO-related complications were bleeding, mostly in the digestive tract (n=4) and airway hemorrhage (n=4), without intracranial hemorrhage, and poor arterial perfusion of the lower limbs (n=2). Among these 15 patients, the overall ICU mortality was 53.3%. The mortality of patients who received VAV-ECMO due to septic shock and cardiogenic shock was 100% (4/4) and 42.8% (3/7), respectively. Two patients who received VAV-ECMO due to lung transplantation all survived. Conclusion: VAV-ECMO may be a safe and effective treatment for carefully selected patients with critical respiratory failure associated with cardiogenic shock or end-stage lung disease lung transplantation transition, however, patients with septic shock may benefit the least.

[The mechanism, inducement and long-term effects of acquired weakness in intensive care units]

With the development of critical care medicine, the case fatality rate in intensive care units (ICU) patients has decreased significantly, but most patients still suffer from the long-term problems of related complications after discharge, which seriously affects the quality of life and social integration after discharge. Complications such as ICU acquired weakness (ICU-AW) and Post-ICU Syndrome (PICS) are not uncommon throughout the treatment of severe patients. The treatment of critically ill patients should not only focus on the treatment of the disease, but also gradually extend to the whole-process physiological-psychological-social medical intervention mode in the ICU, during the stay in the general ward and after discharge. On the basis of ensuring patient safety, patients' physical and psychological status assessment in the early stage of ICU admission, and disease prevention as soon as possible, which can reduce the long-term impact on the quality of life and social work after discharge.

Clinical application of a template-guided automated planning routine

PURPOSE

Determine the dosimetric quality and the planning time reduction when utilizing a template-based automated planning application.

METHODS

A software application integrated through the treatment planning system application programing interface, QuickPlan, was developed to facilitate automated planning using configurable templates for contouring, knowledge-based planning structure matching, field design, and algorithm settings. Validations are performed at various levels of the planning procedure and assist in the evaluation of readiness of the CT image, structure set, and plan layout for automated planning. QuickPlan is evaluated dosimetrically against 22 hippocampal-avoidance whole brain radiotherapy patients. The required times to treatment plan generation are compared for the validations set as well as 10 prospective patients whose plans have been automated by QuickPlan.

RESULTS

The generations of 22 automated treatment plans are compared against a manual replanning using an identical process, resulting in dosimetric differences of minor clinical significance. The target dose to 2% volume and homogeneity index result in significantly decreased values for automated plans, whereas other dose metric evaluations are nonsignificant. The time to generate the treatment plans is reduced for all automated plans with a median difference of 9' 50″ ± 4' 33″.

CONCLUSIONS

Template-based automated planning allows for reduced treatment planning time with consistent optimization structure creation, treatment field creation, plan optimization, and dose calculation with similar dosimetric quality. This process has potential expansion to numerous disease sites.

Semiparametric Efficient G-estimation with Invalid Instrumental Variables

The instrumental variable method is widely used in the health and social sciences for identification and estimation of causal effects in the presence of potential unmeasured confounding. In order to improve efficiency, multiple instruments are routinely used, leading to concerns about bias due to possible violation of the instrumental variable assumptions. To address this concern, we introduce a new class of G-estimators that are guaranteed to remain consistent and asymptotically normal for the causal effect of interest provided that a set of at least γ out of K candidate instruments are valid, for γ≤K set by the analyst ex ante, without necessarily knowing the identity of the valid and invalid instruments. We provide formal semiparametric efficiency theory supporting our results. Both simulation studies and applications to the UK Biobank data demonstrate the superior empirical performance of our estimators compared to competing methods.

Remote Global Radiation Oncology Education and Training: A Pathway to Increase Access to High-Quality Radiation Therapy Services in Low- and Middle-Income Countries

Purpose

There is a vital need to train radiation therapy professionals in low- and middle-income countries (LMICs) to develop sustainable cancer treatment capacity and infrastructure. LMICs have started to introduce intensity modulated radiation therapy (IMRT), which is the standard of care in high-income countries, because of improved outcomes and reduced toxicities. This work reports the efficacy of a complementary asynchronous plus synchronous virtual-training approach on improving radiation therapy professions' self-confidence levels and evaluating participants' attitudes toward asynchronous and synchronous didactic hands-on learning in 3 LMICs.

Methods and Materials

Training was provided to 37 participants from Uganda, Guatemala, and Mongolia, which included 4 theoretical lectures, 4 hands-on sessions, and 8 self-guided online videos. The 36-day training focused on IMRT contouring, site-specific target/organ definition, planning/optimization, and quality assurance. Participants completed pre- and postsession confidence surveys on a 0 to 10 scale, which was converted to a 5-point Likert rating scale to evaluate the training outcomes. The pros and cons of the 3 different training formats were compared.

Results

The participants included 15 (40.5%) radiation oncologists, 11 (29.7%) medical physicists, 6 (16.2%) radiation therapists, and 5 (13.5%) dosimetrists. Approximately 50% had more than 10 years of radiation therapy experience, 70.8% had no formal IMRT training, and only 25% had IMRT at their institutions. The average experience and confidence levels in using IMRT at baseline were 3.2 and 2.9, which increased to 5.2 and 4.9 (P < .001) after the theoretical training. After the hands-on training, the experience and confidence levels further improved to 5.4 and 5.5 (P < .001). After the self-guided training, the confidence levels increased further to 6.9 (P < .01). Among the 3 different training sessions, hands-on trainings (58.3%) were most helpful for the development of participants' IMRT skills, followed by theoretical sessions with 25%.

Conclusions

After completing the training sessions, Uganda and Mongolia started IMRT treatments. Remote training provides an excellent and feasible e-learning platform to train radiation therapy professionals in LMICs. The training program improved the IMRT confidence levels and treatment delivery. The hands-on trainings were most preferred.