Feasibility of surface-guidance combined with CBCT for intra-fractional breath-hold motion management during Ethos RT

PURPOSE

High-quality CBCT and AI-enhanced adaptive planning techniques allow CBCT-guided stereotactic adaptive radiotherapy (CT-STAR) to account for inter-fractional anatomic changes. Studies of intra-fractional respiratory motion management with a surface imaging solution for CT-STAR have not been fully conducted. We investigated intra-fractional motion management in breath-hold Ethos-based CT-STAR and CT-SBRT (stereotactic body non-adaptive radiotherapy) using optical surface imaging combined with onboard CBCTs.

METHODS

Ten cancer patients with mobile lower lung or upper abdominal malignancies participated in an IRB-approved clinical trial (Phase I) of optical surface image-guided Ethos CT-STAR/SBRT. In the clinical trial, a pre-configured gating window (± 2 mm in AP direction) on optical surface imaging was used for manually triggering intra-fractional CBCT acquisition and treatment beam irradiation during breath-hold (seven patients for the end of exhalation and three patients for the end of inhalation). Two inter-fractional CBCTs at the ends of exhalation and inhalation in each fraction were acquired to verify the primary direction and range of the tumor/imaging-surrogate (donut-shaped fiducial) motion. Intra-fractional CBCTs were used to quantify the residual motion of the tumor/imaging-surrogate within the pre-configured breath-hold window in the AP direction. Fifty fractions of Ethos RT were delivered under surface image-guidance: Thirty-two fractions with CT-STAR (adaptive RT) and 18 fractions with CT-SBRT (non-adaptive RT). The residual motion of the tumor was quantified by determining variations in the tumor centroid position. The dosimetric impact on target coverage was calculated based on the residual motion.

RESULTS

We used 46 fractions for the analysis of intra-fractional residual motion and 43 fractions for the inter-fractional motion analysis due to study constraints. Using the image registration method, 43 pairs of inter-fractional CBCTs and 100 intra-fractional CBCTs attached to dose maps were analyzed. In the motion range study (image registration) from the inter-fractional CBCTs, the primary motion (mean ± std) was 16.6 ± 9.2 mm in the SI direction (magnitude: 26.4 ± 11.3 mm) for the tumors and 15.5 ± 7.3 mm in the AP direction (magnitude: 20.4 ± 7.0 mm) for the imaging-surrogate, respectively. The residual motion of the tumor (image registration) from intra-fractional breath-hold CBCTs was 2.2 ± 2.0 mm for SI, 1.4 ± 1.4 mm for RL, and 1.3 ± 1.3 mm for AP directions (magnitude: 3.5 ± 2.1 mm). The ratio of the actual dose coverage to 99%, 90%, and 50% of the target volume decreased by 0.95 ± 0.11, 0.96 ± 0.10, 0.99 ± 0.05, respectively. The mean percentage of the target volume covered by the prescribed dose decreased by 2.8 ± 4.4%.

CONCLUSION

We demonstrated the intra-fractional motion-managed treatment strategy in breath-hold Ethos CT-STAR/SBRT using optical surface imaging and CBCT. While the controlled residual tumor motion measured at 3.5 mm exceeded the predetermined setup value of 2 mm, it is important to note that this motion still fell within the clinically acceptable range defined by the PTV margin of 5 mm. Nonetheless, additional caution is needed with intra-fractional motion management in breath-hold Ethos CT-STAR/SBRT using optical surface imaging and CBCT.

Outcomes of Hepatic Artery-Based Therapies and Systemic Multiagent Chemotherapy in Unresectable Colorectal Liver Metastases: A Systematic Review and Meta-analysis

BACKGROUND

Treatment of unresectable colorectal liver metastases (UCRLM) includes locoregional and systemic therapy. A comprehensive analysis capturing long-term outcomes of these treatment options has not been performed.

OBJECTIVE

A systematic review and meta-analysis was performed to calculate pooled outcomes of hepatic artery infusion with systemic chemotherapy (HAI-S), transarterial chemoembolization with systemic chemotherapy (TACE-S), transarterial radioembolization with systemic chemotherapy (TARE-S), doublet (FOLFOX, FOLFIRI), and triplet chemotherapy (FOLFOXIRI).

METHODS

Outcomes included overall survival (OS), progression-free survival (PFS), rate of conversion to resection (CTR), and response rate (RR).

RESULTS

A total of 32, 7, 9, and 14 publications were included in the HAI-S, TACE-S, and TARE-S chemotherapy arms. The 6/12/24/36-month OS estimates for HAI-S, TACE-S, TARE-S, FOLFOX, FOLFIRI, and FOLFOXIRI were 97%/80%/54%/35%, 100%/83%/40%/14%, 82%/61%/34%/21%, 96%/83%/53%/36%, and 96%/93%/72%/55%. Similarly, the 6/12/24/36-month PFS estimates were 74%/44%/19%/14%, 66%/20%/9%/3%, 57%/23%/10%/3%, 69%/30%/12%/7%, and 88%/55%/18%/11%. The corresponding CTR and RR rates were 31, 20%, unmeasurable (TARE-S), 35, 53; and 49, 45, 45, 50, 80%, respectively. The majority of chemotherapy studies included first-line therapy and liver-only metastases, whereas most HAI-S studies were pretreated. On subgroup analysis in first-line setting with liver-only metastases, the HAI-S arm had comparable outcomes to FOLFOXIRI and outperformed doublet chemotherapy regimens. Although triplet chemotherapy appeared to outperform other arms, high toxicity and inclusion of potentially resectable patients must be considered while interpreting results.

CONCLUSIONS

HAI-S and multiagent chemotherapy are effective therapies for UCRLM. To make definitive conclusions, a randomized trial with comparable patient characteristics and line of therapy will be required. The upcoming EA2222 PUMP trial may help to address this question.

Lateral Pelvic Nodal Management and Patterns of Failure in Patients Receiving Short-Course Radiation for Locally Advanced Rectal Cancer

BACKGROUND

Management of lateral pelvic lymph nodes in locally advanced rectal cancer is controversial, with limited data indicating the optimal approach. In addition, no data exist regarding the treatment of lateral nodes in the setting of short-course radiation and nonoperative intent.

OBJECTIVE

To evaluate a novel approach incorporating simultaneous integrated boost to suspicious lateral nodes.

DESIGN

A retrospective study.

SETTING

This study was conducted at a large tertiary referral center.

PATIENTS

Patients treated with radiation therapy and consolidation chemotherapy were included. All primary tumors underwent biopsy confirmation and disease staging with pelvic MRI.

INTERVENTIONS

Primary tumors were biopsy proven and staged with pelvic MRI. A subset of lateral pelvic lymph node patients received a simultaneous integrated boost of 35 Gy in 5 fractions. Then, chemotherapy was administered, with the majority receiving modified folinic acid, fluorouracil, and oxaliplatin. Clinical partial response required total mesorectal excision.

MAIN OUTCOME MEASURES

Patterns of failure and survival analyses by subgroup were assessed. Outcomes based on receipt of radiation were compared across node status.

RESULTS

Between January 2017 and January 2022, 155 patients were treated with short-course chemotherapy, with 121 included in the final analysis. Forty-nine percent of patients underwent nonoperative management. The median follow-up was 36 months and the median age was 58 years. Thirty-eight patients (26%) had positive lateral pelvic lymph nodes. Comparing lateral node status, progression-free survival was significantly worse for patients with positive disease ( p < 0.001), with a trend for worse overall survival. Receipt of nodal boost in patients with lateral nodes resulted in meaningful locoregional control. Nodal boost did not contribute to additional acute or late GI toxicity.

LIMITATIONS

Limitations include retrospective nature and lack of lateral node pathology; however, a thorough radiographic review was performed.

CONCLUSIONS

Lateral node-positive rectal cancer is correlated with worse oncologic outcomes and higher locoregional failure. Boost to clinically positive lateral nodes is a safe approach in the setting of short course radiation and in those receiving nonoperative intent. See Video Abstract.

MANEJO DE LOS GANGLIOS PLVICOS LATERALES Y PATRONES DE FALLA EN PACIENTES QUE RECIBEN RADIACIN DE CICLO CORTO PARA EL CNCER DE RECTO LOCALMENTE AVANZADO

ANTECEDENTES:El manejo de los ganglios linfáticos pélvicos laterales en el cáncer de recto localmente avanzado es controvertido, con datos limitados que indiquen el abordaje óptimo. Además, no existen datos sobre el tratamiento de los ganglios linfáticos laterales en el contexto de la radiación de curso corto y la intención no operatoria.OBJETIVO:Evaluamos un enfoque novedoso que incorpora sobreimpresión integrada simultánea (SIB) a los linfonodos laterales sospechosos.DISEÑO:Este fue un estudio retrospectivo.ESCENARIO:Este estudio se realizó en un gran centro de referencia terciario.PACIENTES:Se incluyeron pacientes tratados con radiación y quimioterapia de consolidación. Todos los tumores primarios se confirmaron mediante biopsia y la enfermedad se estadificó con resonancia magnética pélvica.INTERVENCIONES:Los tumores primarios se confirmaron mediante biopsia y se estadificaron con RM pélvica. Un subconjunto de pacientes con linfonodos pélvicos laterales (LPLN) recibió SIB a 35 Gy en 5 fracciones. Luego, se administró quimioterapia y la mayoría recibió mFOLFOX. La respuesta clínica parcial requirió la escisión total del mesorrecto.PRINCIPALES MEDIDAS DE RESULTADO:Se evaluaron los patrones de fracaso y los análisis de supervivencia por subgrupo. Los resultados basados en el esquema de radiación se compararon según el estado de los ganglios.RESULTADOS:Entre enero de 2017 y enero de 2022, 155 pacientes fueron tratados con ciclo corto y quimioterapia con 121 incluidos en el análisis final. El 49% se sometió a manejo no operatorio. La mediana de seguimiento fue de 36 meses y la mediana de edad fue de 58 años. 38 pacientes (26%) tuvieron LPLN positivos. Comparando el estado de los ganglios laterales, la supervivencia libre de progresión fue significativamente peor para los pacientes con LPLN positiva ( p < 0,001) con una tendencia a una peor supervivencia global. La recepción de refuerzo nodal en pacientes con nodos laterales dio como resultado un control locorregional significativo. La sobreimpresión ganglionar no contribuyó a la toxicidad GI aguda o tardía adicional.LIMITACIONES:Las limitaciones incluyeron la naturaleza retrospectiva y la falta de patología de los ganglios linfáticos laterales; sin embargo, se realizó una revisión radiográfica exhaustiva.CONCLUSIONES:El cáncer de recto con ganglio lateral positivo se correlaciona con peores resultados oncológicos y mayor fracaso locorregional. La sobreimpresión a los ganglios laterales clínicamente positivos es un enfoque seguro en el contexto de un curso corto y en aquellos que siguen un manejo no operatorio. (Traducción-Dr. Felipe Bellolio ).

A feasibility trial of skin surface motion-gated stereotactic body radiotherapy for treatment of upper abdominal or lower thoracic targets using a novel O-ring gantry

Background and purpose

A novel O-ring gantry can deliver stereotactic body radiation therapy (SBRT) with artificial intelligence-facilitated, CT-guided online plan adaptation. It gates mobile targets by optically monitoring skin surface motion. However, this gating solution has not been clinically validated. We conducted a trial to evaluate the feasibility of optical skin surface-guided gating for patients with mobile upper abdominal or lower thoracic malignancies treated with SBRT on this platform (NCT05030454).

Materials and methods

Ten patients who were prescribed SBRT to a thoracic or abdominal target and were capable of breath-hold for at least 17 s enrolled. They received SBRT in five fractions with breath-hold technique and optical skin surface motion monitored-gating with a ± 2 mm tolerance. Online plan adaptation was left to the discretion of the daily treating physician. The primary endpoint was defined as successful completion of > 75 % of attempted fractions. Exploratory endpoints included local control and acute grade ≥ 3 toxicity rates after three months. For adapted fractions the contouring, planning, quality assurance, and treatment delivery times were recorded.

Results

Forty-seven of 51 SBRT fractions (92 %) were successfully gated at breath-hold by optical skin surface motion monitoring. The tumor centroid position during breath-hold varied by a mean of approximately 2 mm. Sixty-three percent of fractions were adapted online with a median total treatment time of 78.5 min. After three months no local recurrences or acute grade ≥ 3 toxicities were observed.

Conclusions

SBRT treatment to mobile targets with surface-monitored gating on a novel O-ring gantry was prospectively validated.

CT-based online adaptive radiotherapy improves target coverage and organ at risk (OAR) avoidance in stereotactic body radiation therapy (SBRT) for prostate cancer

Introduction

Stereotactic body radiation therapy (SBRT) is an emerging treatment modality for clinically localized prostate cancer (PCa). Online daily adaptive radiotherapy (ART) could potentially improve the therapeutic ratio of prostate SBRT by accounting for inter-fraction variation in target and OAR volumes. To our knowledge, no group has evaluated the clinical utility of a novel AI-augmented CT-based ART system for prostate SBRT. In this study we hypothesized that adaptive prostate SBRT plans would result in improved target coverage and lower dose to OARs in comparison to unadapted treatment plans.

Methods

Seven patients with favorable intermediate to oligometastatic PCa treated with 5-fx prostate adaptive SBRT were retrospectively reviewed. Patients were treated with 3625 cGy to the prostate and seminal vesicles. 6 patients additionally received 2500 cGy to the pelvic nodes, 5 patients underwent a boost to 4000 cGy to the prostate. For each fraction, a CBCT was acquired and OARs (rectum, bladder, bowel, sigmoid, femurs) were segmented/deformed using AI. CTVs were rigidly registered. Volumes were adjusted manually and PTV expansions added. Adaptive treatment plans were developed based on the contoured targets and OARs and dose to these volumes for the adapted vs. initial plans were compared for each fraction. V100 and the D0.03 cc between scheduled and adapted treatment plans were compared using a Student's t-test, with significance threshold of P < 0.05.

Results

Seven patients completed 35 Fx's of adaptive RT. Daily adaptation resulted in a statistically significant mean improvement in PTV V100 for all targets: [21.4 % ± 4.3 % for PTV 4000 (p < 0.0001); 8.7 % ± 1.1 % for PTV 3625 (p < 0.0001); and 11.5 % ± 3.1 % for PTV 2500 (p = 0.0013)]. Mean rectal D0.03 was significantly reduced by 38.8 cGy ± 5.95 cGy (p < 0.0001) per fraction (194 cGy/5 fractions) compared to the initial plans. There was a modest increase in bladder dose of 10.9 cGy ± 4.93 cGy per fraction (p = 0.0424) for the adaptive plans. The adaptive plans met bladder constraints for every fraction. There were no statistically significant differences between sigmoid or bowel dose for adapted vs. initial plans. No patients experienced acute CTCAE grade ≥ 3 GI/GU adverse events (median F/U 9.5 months). All statistically significant differences were maintained in the presence and absence of rectal hydrogel spacer (p < 0.05).

Conclusions

CT-based online adaptive SBRT resulted in statistically significant and clinically meaningful improvements in PTV coverage and D0.03 cc dose to the rectum. A trial evaluating CT adaptive whole-pelvis prostate SBRT is underway.

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.

Phantom-based Quality Assurance of a Clinical Dose Accumulation Technique Used in an Online Adaptive Radiation Therapy Platform

Purpose

This study aimed to develop a routine quality assurance method for a dose accumulation technique provided by a radiation therapy platform for online treatment adaptation.

Methods and Materials

Two commonly used phantoms were selected for the dose accumulation QA: Electron density and anthropomorphic pelvis. On a computed tomography (CT) scan of the electron density phantom, 1 target (gross tumor volume [GTV]; insert at 6 o'clock), a subvolume within this target, and 7 organs at risk (OARs; other inserts) were contoured in the treatment planning system (TPS). Two adaptation sessions were performed in which the GTV was recontoured, first at 7 o'clock and then at 5 o'clock. The accumulated dose was exported from the TPS after delivery. Deformable vector fields were also exported to manually accumulate doses for comparison. For the pelvis phantom, synthetic Gaussian deformations were applied to the planning CT image to simulate organ changes. Two single-fraction adaptive plans were created based on the deformed planning CT and cone beam CT images acquired onboard the radiation therapy platform. A manual dose accumulation was performed after delivery using the exported deformable vector fields for comparison with the system-generated result.

Results

All plans were successfully delivered, and the accumulated dose was both manually calculated and derived from the TPS. For the electron density phantom, the average mean dose differences in the GTV, boost volume, and OARs 1 to 7 were 0.0%, -0.2%, 92.0%, 78.4%, 1.8%, 1.9%, 0.0%, 0.0%, and 2.3%, respectively, between the manually summed and platform-accumulated doses. The gamma passing rates for the 3-dimensional dose comparison between the manually generated and TPS-provided dose accumulations were >99% for both phantoms.

Conclusions

This study demonstrated agreement between manually obtained and TPS-generated accumulated doses in terms of both mean structure doses and local 3-dimensional dose distributions. Large disagreements were observed for OAR1 and OAR2 defined on the electron density phantom due to OARs having lower deformation priority over the target in addition to artificially large changes in position induced for these structures fraction-by-fraction. The tests applied in this study to a commercial platform provide a straightforward approach toward the development of routine quality assurance of dose accumulation in online adaptation.

Abstract B020: Biomarkers of IDO1 inhibition in patients with locally advanced rectal cancer treated with radiation and chemotherapy

Background: To date, immunotherapy has not advanced the initial care of locally advanced rectal cancer (LARC) where a combination of radiation and chemotherapy remains the standard of care. In evaluation of other targets, we identified that the immune-oncology target indoleamine 2,3 dioxygenase-1 (IDO1) is universally overexpressed in rectal cancers after radiation therapy (RT) regardless of MSI status. IDO1 initiates tryptophan metabolism along the kynurenine pathway (KP) and activation of the KP exerts immune-suppressive effects in the tumor microenvironment. Our preclinical data identified that epacadostat, a potent inhibitor of IDO1, reduced CRC growth in vitro and in vivo. Furthermore, we found that epacadostat augmented the anti-tumor effects of RT by directly increasing apoptosis in neoplastic cells as well as by relieving RT induced immune-suppression. Based on these findings, we initiated a Phase I study in patients with LARC where epacadostat was used in combination with short-course RT (5 Gy x 5) and chemotherapy. This study is ongoing with the primary endpoint of determining the recommended phase II dose (RP2D) of epacadostat in this population. The study is a dose escalating design including 300, 400, and 600 mg BID. Aim: To present preliminary results from the corollary studies on sequentially acquired biospecimens. Methods: We collected tumor tissue and blood pre-treatment, post-radiation/pre-chemo, sequentially throughout chemo, and at treatment completion or surgery. Analyses include global metabolomics, focused evaluation of tryptophan pathway metabolites, single cell RNAseq, flow cytometry, ctDNA and tissue analysis for IDO1 and other immune checkpoint targets. We also established tumor-derived organoids/tumoroids and have established a “tumor-on-a-chip” model to conduct ex vivo tumor modeling. Results: Preliminary studies confirm an elevation of kynurenine to tryptophan ratio after SCRT which is reversed by epacadostat. Changes in the global metabolomics profiles and immune profiles shift from baseline through the stages of SCRT and chemotherapy revealing consistent patterns. Changes in ctDNA were assessed using the CAPP-Seq based AVENIO platform providing a personalized oncogenomic analysis and demonstrated of rapid clearance from post-SCRT which persisted throughout chemotherapy. Studies with tumoroids and the analysis of scRNAseq data are ongoing and will be presented. Conclusions: Preliminary analysis of biospecimens from this actively accruing study of epacadostat plus RT and chemotherapy reveals distinct changes in metabolomic, immunologic, and genomic profiling across the stages of treatment. These results have the potential to inform a precision design for the Phase II study and will also inform the most promising disease and treatment related biomarkers.

Citation Format: Matthew A. Ciorba, Katrina Pedersen, Lauren Henke, Aadel Chaudhuri, Matthew Mutch, Hyun Kim, Haeseong Park. Biomarkers of IDO1 inhibition in patients with locally advanced rectal cancer treated with radiation and chemotherapy [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr B020.

LITE SABR M1: A phase I trial of Lattice stereotactic body radiotherapy for large tumors

PURPOSE

Stereotactic body radiotherapy (SBRT) is an attractive treatment option for patients with metastatic and/or unresectable tumors, however its use is limited to smaller tumors. Lattice is a form of spatially fractionated radiotherapy that may allow safe delivery of ablative doses to bulky tumors. We previously described Lattice SBRT, which delivers 20 Gy in 5 fractions with a simultaneous integrated boost to 66.7 Gy in a defined geometric arrangement (Lattice boost). The goal of this study was to prospectively evaluate the acute toxicity and quality of life (QoL) of patients with large tumors (>5 cm) treated with Lattice SBRT.

METHODS

This was a single-arm phase I trial conducted between October 2019 and August 2020. Patients with tumors > 4.5 cm were eligible. Lattice SBRT was delivered every other day. The primary outcome was the rate of 90-day treatment-associated (probably or definitely attributable) grade 3 + acute toxicity by Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 criteria. Other outcomes included changes in patient reported toxicity and QoL inventories, GTV, and peripheral blood cytokines.

RESULTS

Twenty patients (22 tumors) were enrolled. Median GTV was 579.2 cc (range: 54.2-3713.5 cc) in volume and 11.1 cm (range: 5.6-21.4 cm) in greatest axial diameter. Fifty percent of tumors were in the thorax, 45% abdomen/pelvis, and 5% extremity. There was no likely treatment-associated grade 3 + toxicity in the 90-day period (acute and sub-acute). There was one case of grade 4 toxicity possibly associated with Lattice SBRT.

CONCLUSIONS

This phase I study met its primary endpoint of physician reported short-term safety. An ongoing phase II clinical trial of Lattice SBRT will evaluate late safety and efficacy of this novel technique.

Visually guided respiratory motion management for Ethos adaptive radiotherapy

Purpose

Ethos adaptive radiotherapy (ART) is emerging with AI‐enhanced adaptive planning and high‐quality cone‐beam computed tomography (CBCT). Although a respiratory motion management solution is critical for reducing motion artifacts on abdominothoracic CBCT and improving tumor motion control during beam delivery, our institutional Ethos system has not incorporated a commercial solution. Here we developed an institutional visually guided respiratory motion management system to coach patients in regular breathing or breath hold during intrafractional CBCT scans and beam delivery with Ethos ART.

Methods

The institutional visual‐guidance respiratory motion management system has three components: (1) a respiratory motion detection system, (2) an in‐room display system, and (3) a respiratory motion trace management software. Each component has been developed and implemented in the clinical Ethos ART workflow. The applicability of the solution was demonstrated in installation, routine QA, and clinical workflow.

Results

An air pressure sensor has been utilized to detect patient respiratory motion in real time. Either a commercial or in‐house software handled respiratory motion trace display, collection and visualization for operators, and visual guidance for patients. An extended screen and a projector on an adjustable stand were installed as the in‐room visual guidance solution for the closed‐bore ring gantry medical linear accelerator utilized by Ethos. Consistent respiratory motion traces and organ positions on intrafractional CBCTs demonstrated the clinical suitability of the proposed solution in Ethos ART.

Conclusion

The study demonstrated the utilization of an institutional visually guided respiratory motion management system for Ethos ART. The proposed solution can be easily applied for Ethos ART and adapted for use with any closed bore‐type system, such as computed tomography and magnetic resonance imaging, through incorporation with appropriate respiratory motion sensors.

A single-institution phase I feasibility study of dose-escalated IMRT for non-operative locally advanced esophageal carcinoma

•

Dose escalation with IMRT to 60 Gy for esophageal cancer is feasible.

•

Dose escalation with cisplatin/5-FU still results in significant toxicity.

•

Improved local control, but comparable survival compared to historical controls.

•

Pretreatment weight loss was found to be an independent predictor of poor survival.

•

Our dose escalation study is one of few with predominant adenocarcinoma histology.

Background and purpose

Radiation dose escalation to improve poor outcomes with chemoradiation in locally advanced esophageal carcinoma is limited in part by increased toxicity. This Phase I study investigates the use of IMRT to improve tolerability of dose escalation.

Materials and methods

A single-institution, prospective study was conducted between 2007 and 2013 for individuals with inoperable esophageal carcinoma. Gross disease received 60 Gy in 30 fractions and at-risk sites received 54 Gy with simultaneous integrated boost. Concurrent chemotherapy primarily consisted of cisplatin/5-FU. The primary objective was to assess feasibility (<15% rate of grade 4–5 toxicity). Secondary objectives included assessment of overall survival (OS), progression free survival (PFS), and locoregional (LRR) and distant recurrence.

Results

Twenty-six patients were enrolled with median follow up of 17.6 months (range 0.1 to 152.0). The majority were AJCC 7th edition Stage III (54%), distal esophagus primary (81%), and adenocarcinoma histology (85%). Twenty-one patients (81%) completed their course of radiation therapy, while only 55% received 2 cycles of concurrent cisplatin/5-FU. One grade 5 and one grade 4 cardiac event occurred, both during chemoradiation and before receiving 50 Gy. The 3-year OS was 48.6% (95% CI: 32.5 to 72.2%) and PFS was 28.5% (95% CI: 14.6 to 55.5%). Half developed distant failure with LRR occurring in 10 patients (38%), isolated in 5 patients.

Conclusion

While feasibility was demonstrated, toxicity and compliance remained limiting factors with outcomes similar to historical controls. There remains an uncertain role for dose escalation in definitive management of locally advanced esophageal cancer.

Technical Note: Self-shielding evaluation and radiation leakage measurement of a jawless ring gantry linac with a beam stopper

PURPOSE

To characterize the shielding design and leakage radiation from a newly released ring gantry linac (Halcyon, Varian Medical Systems).

METHODS

To assess the radiation leakage surrounding headshield and the radiation level after the beam stopper, measurements were made with GafChromic films. To evaluate the in-room radiation levels, the radiation leakage in the isocenter plane was measured with a large volume spherical ionization chamber (Exradin A6, Standard Imaging). A lead enclosure was constructed to shield the chamber from the low energy scatter radiation from the room. The radiation level at multiple locations was measured with the MLC fully closed and gantry at 0, 45, 90, 135, 180, 225, 270, and 315 degrees. The leakage radiation passing through multiple concrete slabs with various thickness was recorded in a narrow beam geometry to determine the tenth value layer (TVL).

RESULTS

A uniform leakage (<0.05%) at 1 m from electron beam line was measured surrounding the linac head with the maximum leakage measured at the top of the head enclosure. The highest radiation level (<0.08%) was measured near the edge of the beam stopper when projected to the measurement plane. The maximum radiation levels due to the head leakage at 15 locations inside the treatment room were recorded and a radiation map was plotted. The maximum leakage was measured at points that along the electron beam line while the gantry at 90 or 270 degree and at the end of head enclosure (0.314%, 0.4 m from electron beamline). The leakage TVL value is found to be 226 mm in a narrow beam geometry with the concrete density of 2.16 g/cm³ or 134.6 lb/cu.ft.

CONCLUSION

An overall uniform leakage was measured surrounding linac head. The beam stopper shields the primary radiation with the highest valued measured near the edge of beam stopper. The leakage TVL values are derived and less than the values reported for conventional C-arm linac.

MR-Guided Radiotherapy for Liver Malignancies

MR guided radiotherapy represents one of the most promising recent technological innovations in the field. The possibility to better visualize therapy volumes, coupled with the innovative online adaptive radiotherapy and motion management approaches, paves the way to more efficient treatment delivery and may be translated in better clinical outcomes both in terms of response and reduced toxicity. The aim of this review is to present the existing evidence about MRgRT applications for liver malignancies, discussing the potential clinical advantages and the current pitfalls of this new technology.

Direct tumor visual feedback during free breathing in 0.35T MRgRT

To present a tumor motion control system during free breathing using direct tumor visual feedback to patients in 0.35 T magnetic resonance-guided radiotherapy (MRgRT). We present direct tumor visualization to patients by projecting real-time cine MR images on an MR-compatible display system inside a 0.35 T MRgRT bore. The direct tumor visualization included anatomical images with a target contour and an auto-segmented gating contour. In addition, a beam-status sign was added for patient guidance. The feasibility was investigated with a six-patient clinical evaluation of the system in terms of tumor motion range and beam-on time. Seven patients without visual guidance were used for comparison. Positions of the tumor and the auto-segmented gating contour from the cine MR images were used in probability analysis to evaluate tumor motion control. In addition, beam-on time was recorded to assess the efficacy of the visual feedback system. The direct tumor visualization system was developed and implemented in our clinic. The target contour extended 3 mm outside of the gating contour for 33.6 ± 24.9% of the time without visual guidance, and 37.2 ± 26.4% of the time with visual guidance. The average maximum motion outside of the gating contour was 14.4 ± 11.1 mm without and 13.0 ± 7.9 mm with visual guidance. Beam-on time as a percentage was 43.9 ± 15.3% without visual guidance, and 48.0 ± 21.2% with visual guidance, but was not significantly different (P = 0.34). We demonstrated the clinical feasibility and potential benefits of presenting direct tumor visual feedback to patients in MRgRT. The visual feedback allows patients to visualize and attempt to minimize tumor motion in free breathing. The proposed system and associated clinical workflow can be easily adapted for any type of MRgRT.

Abstract CT234: Phase I study of epacadostat added to preoperative chemoradiation in patients with locally advanced rectal cancer

Background: Epacadostat is an orally active, potent and selective inhibitor of indoleamine 2, 3-dioxygenase 1 (IDO1). IDO1 inhibition enhances cytotoxic T cell activation by dendritic cells, and significantly decreases regulatory T cell proliferation. We developed preclinical data supporting combination of epacadostat with radiation therapy in rectal cancer. In rectal cancer samples obtained from patients who received hypofractionated radiation, IDO1 was overexpressed in tumor tissue as compensatory response after radiation in both microsatellite stable and unstable cell lines. IDO1 inhibition with epacadostat selectively reduced survival of cancer cells and enhanced radiosensitivity without impacting normal epithelial cells. Epacadostat in addition to radiation showed both increased tumor cytotoxicity and enhanced immune activation in tumor microenvironment in a syngeneic mouse model of colorectal cancer. Literature also supports the choice of high dose, hypofractionated radiation to induce a more favorable anti-tumor immune response. Therefore, we hypothesized that IDO1 expression is a mechanism of radioresistance in rectal cancer and IDO1 inhibition is a safe and well-tolerated combination therapy to enhance tumor radiosensitivity. Methods: Patients with locally advanced rectal cancer who are candidates for neoadjuvant therapy using short-course radiation and chemotherapy are included in this study. Primary objective of the study is to determine the recommended phase II dose (RP2D) of epacadostat for combination with short course radiation and chemotherapy in preoperative treatment of locally advanced rectal cancer. This study includes dose-escalation part of patients receiving epacadostat with radiation and chemotherapy (n=6-18) followed by dose-expansion (n=up to 27 including those treated at RP2D during escalation). Two dose levels of epacadostat (300mg and 600mg orally twice daily) will be explored. Epacadostat will be combined with short-course radiation (5Gy x 5 fractions) followed by 6 cycles of CAPOX chemotherapy, until the day of surgery for a total of approximately 24 weeks of therapy. Research biopsies of tumor and adjacent non-tumor tissue along with blood sample collection will be performed before and after the radiation, and at the time of surgery. Tryptophan pathway metabolites, immune checkpoint biomarkers, markers of cell death, proliferation and potentially prognostic molecular biomarkers will be measured in tumor tissues before and after radiation therapy. In addition, patient-derived organoid and xenograft models from rectal biopsy samples will be used to determine the success rate of organoid generation, to evaluate treatment response and to characterize molecular changes to identify potential predictors of response and mechanisms of resistance. Enrollment began in November 2019. NCT03516708

Citation Format: Haeseong Park, Ebunoluwa Otegbeye, Hyun Kim, Matthew Mutch, Katrina Pedersen, Manik Amin, Benjamin Tan, Nikolaos Trikalinos, Kian-Huat Lim, Olivia Aranha, Rama Suresh, Shahed Badiyan, Matthew Silviera, Lauren Henke, Paul Wise, Steven Hunt, Jonathan Mitchem, Esther Lu, Andrea Wang-Gillam, Matthew Ciorba. Phase I study of epacadostat added to preoperative chemoradiation in patients with locally advanced rectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT234.

Taking Guatemala From Cobalt to IMRT: A Tale of US Agency Collaboration With Academic Institutions and Industry

The not-for-profit organization La LIGA Nacional Contra el Cáncer, with its hospital Instituto de Cancerología (INCAN), is responsible for cancer treatment of much of the indigent population in Guatemala, a country with a population of 16 million. Annually, approximately 70% of patients at INCAN are seen in late stages of cancer, which places a great strain on the hospital's limited resources. Private clinics account for 75% of radiation therapy centers in Guatemala and have considerable resources. However, private facilities are fee-based, which creates a barrier for low-income patients; this is an especially significant problem in Guatemala, which has the highest income inequalities and poverty rates in Latin America. This article describes a project on the transition from cobalt to a Halcyon radiation therapy system at INCAN through a partnership with the US Agency for International Development's Office of American Schools and Hospitals Abroad (USAID/ASHA), Washington University in St. Louis (WUSTL), industry partner Varian Medical Systems, and the US National Nuclear Security Administration to provide access to state-of-the-art radiation therapy technology while increasing the overall treatment capacity for the underserved population of Guatemala.

Ablative Five-Fraction Stereotactic Body Radiation Therapy for Inoperable Pancreatic Cancer Using Online MR-Guided Adaptation

Purpose

Patients with inoperable pancreatic adenocarcinoma have limited options, with traditional chemoradiation providing modest clinical benefit and an otherwise poor prognosis. Stereotactic body radiation therapy for pancreatic cancer is limited by proximity to organs-at-risk (OAR). However, stereotactic magnetic resonance-guided adaptive radiation therapy (SMART) has shown promise in delivering ablative doses safely. We sought to demonstrate the benefits of SMART using a 5-fraction approach with daily on-table adaptation.

Methods and Materials

Patients with locally advanced, nonmetastatic pancreatic adenocarcinoma were treated with 50 Gy in 5 fractions (biologically effective dose₁₀ 100 Gy) with a prescribed goal of 95% planning target volume coverage by 95% of prescription, prioritizing hard OAR constraints. Daily online adaptation was performed using magnetic resonance-guidance and on-table reoptimization. Patient outcomes, treatment factors, and daily adaptation were evaluated.

Results

Forty-four patients were treated with SMART at our institution from 2014 to 2019. Median follow-up from date of diagnosis was 16 months (range, 6.7-51.6). Late toxicity was limited to 2 (4.6%) grade 3 (gastrointestinal ulcers) and 3 (6.8%) grade 2 toxicities (duodenal perforation, antral ulcer, and gastric bleed). Tumor abutted OARs in 35 patients (79.5%) and tumor invaded OARs in 5 patients (11.1%). Reoptimization was performed for 93% of all fractions. Median overall survival was 15.7 months (95% confidence interval, 10.2-21.2), while 1-year and 2-year overall survival rates were 68.2% and 37.9%, respectively. One-year local control was 84.3%.

Conclusions

This is the first reported experience using 50 Gy in 5 fractions for inoperable pancreatic cancer. SMART allows this ablative dose with promising outcomes while minimizing toxicity. Additional prospective trials evaluating efficacy and safety are warranted.

MRI-Based Upper Abdominal Organs-at-Risk Atlas for Radiation Oncology

PURPOSE

The purpose of our study was to provide a guide for identification and contouring of upper abdominal organs-at-risk (OARs) in the setting of online magnetic resonance imaging (MRI)-guided radiation treatment planning and delivery.

METHODS AND MATERIALS

After a needs assessment survey, it was determined that an upper abdominal MRI-based atlas of normal OARs would be of benefit to radiation oncologists and radiation therapists. An anonymized diagnostic 1.5T MRI from a patient with typical upper abdominal anatomy was used for atlas development. Two MRI sequences were selected for contouring, a T1-weighted gadoxetic acid contrast-enhanced MRI acquired in the hepatobiliary phase and axial fast imaging with balanced steady-state precession. Two additional clinical MRI sequences from commercial online MRI-guided radiation therapy systems were selected for contouring and were included in the final atlas. Contours from each data set were completed and reviewed by radiation oncologists, along with a radiologist who specializes in upper abdominal imaging, to generate a consensus upper abdominal MRI-based OAR atlas.

RESULTS

A normal OAR atlas was developed, including recommendations for contouring. The atlas and contouring guidance are described, and high-resolution MRI images and contours are displayed. OARs, such as the bile duct and biliary tree, which may be better seen on MRI than on computed tomography, are highlighted. The full DICOM/DICOM-RT MRI images from both the diagnostic and clinical online MRI-guided radiation therapy systems data sets have been made freely available, for educational purposes, at econtour.org.

CONCLUSIONS

This MRI contouring atlas for upper abdominal OARs should provide a useful reference for contouring and education. Its routine use may help to improve uniformity in contouring in radiation oncology planning and OAR dose calculation. Full DICOM/DICOM-RT images are available online and provide a valuable educational resource for upper abdominal MRI-based radiation therapy planning and delivery.

MRI safety risks in the obese: The case of the disposable lighter stored in the pannus

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Obese patients are subject to higher MRI risks than lower weight patients.

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Obese patients typically require additional setup and acquisition times for MRI.

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Unanticipated safety threats may arise in obese patients despite vigilant screening.

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Threats to MRI safety may impact other clinical procedures.

Obese patients constitute 40% of the adult population. MRIs of obese patients are typically challenging because of the effects of a large field of view on image quality and the increased risk of thermal burns from contact with the bore. In this case report, the impacts of obesity on MRI procedures and safety are introduced. Then a case is presented of a 30-year old female cervical cancer patient who received an MRI simulation to verify the placement of a titanium tandem and colpostats for brachytherapy. A large magnetic susceptibility artifact was detected near the right pelvis during the MRI scout indicating the presence of ferrous material. The source of the artifact turned out to be a disposable lighter that was stored inside the patient's pannus. The finding highlights an unanticipated risk to MRI safety and image quality associated with large body habitus.

A molecular approach combined with American Thyroid Association classification better stratifies recurrence risk of classic histology papillary thyroid cancer

BACKGROUND

Prognosis among patients with differentiated thyroid cancer is widely variable. Better understanding of biologic subtypes is necessary to stratify patients and improve outcomes.

METHODS

In patients diagnosed with classic histology papillary thyroid cancer treated from 1973 to 2009, BRAF V600E mutation status was determined on surgical tumor specimens by restriction fragment length polymorphism analysis. A tissue microarray (TMA) was constructed from tumor specimens in triplicate and stained by immunohistochemistry for RET, phospho-MEK, MAPK(dpERK), PPARγ, and phospho-AKT(pAKT). Stained slides were scored independently and blindly by two investigators and compared to tumor and patient characteristics and outcomes.

RESULTS

A total of 231 patients had archived formalin-fixed, paraffin-embedded tumor tissue available and were included on the TMA. Mean age at diagnosis was 44 years (range 6-82 years); proportion of patients with female sex was (72%); 2015 American Thyroid Association (ATA) risk stratification was low (26%), intermediate (32%), and high (42%). BRAF V600E mutation was found in 74% of specimens, and IHC was scored as positive for RET (61%), MAPK (dpERK) (14%), PPARγ (27%), and pAKT (39%). Positive RET staining was associated with a lower risk of recurrence (HR = 0.46, 95% CI 0.22-0.96). No other molecular biomarkers were independent predictors of recurrence on univariable analysis. On RPA, patients with RET-negative and either MAPK(dpERK)-positive or pAKT-positive tumors were identified to have a high risk of recurrence (HR = 5.4, 95%CI 2.5-11.7). This profile remained associated with recurrence in a multivariable model including ATA risk stratification (HR = 2.8, 95% CI 1.3-6.0).

CONCLUSION

Characterization of molecular pathways involved in cPTC tumorigenesis may add further risk stratification for recurrence beyond the 2015 ATA risk categories alone.

A novel MRI segmentation method using CNN-based correction network for MRI-guided adaptive radiotherapy

PURPOSE

The purpose of this study was to expedite the contouring process for MRI-guided adaptive radiotherapy (MR-IGART), a convolutional neural network (CNN) deep-learning (DL) model is proposed to accurately segment the liver, kidneys, stomach, bowel and duodenum in 3D MR images.

METHODS

Images and structure contours for 120 patients were collected retrospectively. Treatment sites included pancreas, liver, stomach, adrenal gland, and prostate. The proposed DL model contains a voxel-wise label prediction CNN and a correction network which consists of two sub-networks. The prediction CNN and sub-networks in the correction network each includes a dense block which consists of twelve densely connected convolutional layers. The correction network was designed to improve the voxel-wise labeling accuracy of a CNN by learning and enforcing implicit anatomical constraints in the segmentation process. Its sub-networks learn to fix the erroneous classification of its previous network by taking as input both the original images and the softmax probability maps generated from its previous sub-network. The parameters of each sub-network were trained independently using piecewise training. The model was trained on 100 datasets, validated on 10 datasets and tested on the remaining 10 datasets. Dice coefficient, Hausdorff distance (HD) were calculated to evaluate the segmentation accuracy.

RESULTS

The proposed DL model was able to segment the organs with good accuracy. The correction network outperformed the conditional random field (CRF), a most comparable method that is usually applied as a post-processing step. For the 10 testing patients, the average Dice coefficients were 95.3 ± 0.73, 93.1 ± 2.22, 85.0 ± 3.75, 86.6 ± 2.69, and 65.5 ± 8.90 for liver, kidneys, stomach, bowel, and duodenum, respectively. The mean Hausdorff Distance (HD) were 5.41 ± 2.34, 6.23 ± 4.59, 6.88 ± 4.89, 5.90 ± 4.05, and 7.99 ± 6.84 mm, respectively. Manual contouring, as to correct the automatic segmentation results, was four times as fast as manual contouring from scratch.

CONCLUSION

The proposed method can automatically segment the liver, kidneys, stomach, bowel, and duodenum in 3D MR images with good accuracy. It is useful to expedite the manual contouring for MR-IGART.

Palliative radiation therapy (RT) for prostate cancer patients with bone metastases at diagnosis: A hospital-based analysis of patterns of care, RT fractionation scheme, and overall survival

Prostate cancer (PCa) is one of the most common malignancies associated with bone metastases, and palliative radiation therapy (RT) is an effective treatment option. A total of 2641 patients were identified with PCa and bone metastases at diagnosis from 2010 to 2014 in the NCDB. Fractionation scheme was designated as short course ([SC‐RT]: 8 Gy in 1 fraction and 20 Gy in 5 fractions) vs long course ([LC‐RT]: 30 Gy in 10 fractions and 37.5 Gy in 15 fractions). Patient characteristics were correlated with fractionation scheme using logistic regression. Overall survival was analyzed using the Kaplan‐Meier method, log‐rank test, Cox proportional hazards models, and propensity score‐matched analyses. A total of 2255 (85.4%) patients were included in the LC‐RT group and 386 (14.6%) patients in the SC‐RT group. SC‐RT was more common in patients over 75 years age (odds ratio [OR]: 1.70, 95% confidence interval [CI] 1.32‐2.20), treatment at an academic center (OR: 1.76, 1.20‐2.57), living greater than 15 miles distance to treatment facility (OR: 1.38, 1.05‐1.83), treatment to the rib (OR: 2.99, 1.36‐6.60), and in 2014 (OR: 1.73, 1.19‐2.51). RT to the spine was more commonly long course (P < .0001). In the propensity‐matched cohort, LC‐RT was associated with improved OS (P < .0001), but no OS difference was observed between 37.5 Gy and either 8 Gy in one fraction or 20 Gy in 5 fractions (P > .5). LC‐RT remains the most common treatment fractionation scheme for palliative bone metastases in PCa patients. Use of palliative SC‐RT is increasing, particularly in more recent years, for older patients, treatment at academic centers, and with increasing distance from a treatment center.

Two-and-a-half-year clinical experience with the world's first magnetic resonance image guided radiation therapy system

Purpose

Magnetic resonance image guided radiation therapy (MR-IGRT) has been used at our institution since 2014. We report on more than 2 years of clinical experience in treating patients with the world's first MR-IGRT system.

Methods and materials

A clinical service was opened for MR-IGRT in January 2014 with an MR-IGRT system consisting of a split 0.35T magnetic resonance scanner that straddles a ring gantry with 3 multileaf collimator-equipped ⁶⁰Co heads. The service was expanded to include online adaptive radiation therapy (ART) MR-IGRT and cine gating after 6 and 9 months, respectively. Patients selected for MR-IGRT were enrolled in a prospective registry between January 2014 and June 2016. Patients were treated with a variety of radiation therapy techniques including intensity modulated radiation therapy and stereotactic body radiation therapy (SBRT). When applicable, online ART was performed and gating on sagittal 2-dimensional cine MR was used. The charts of patients treated with MR-IGRT were reviewed to report on the clinical and treatment characteristics of the initial patients who were treated with this novel technique.

Results

A total of 316 patients have been treated with the MR-IGRT system, which has been integrated into a high-volume clinic. The cases were most commonly selected for improved soft tissue visualization, ART, and cine gating. Seventy-six patients were treated with 3-dimensional conformal radiation therapy, 146 patients with intensity modulated radiation therapy, and 94 patients with SBRT. The most commonly treated disease sites were the abdomen (28%), breast (26%), pelvis (22%), thorax (19%), and head and neck (5%). Sixty-seven patients were treated with online ART over a total of 244 adapted fractions. Cine treatment gating was used for a total of 81 patients.

Conclusions

MR-IGRT has been successfully implemented in a high-volume radiation clinic and provides unique advantages in the treatment of a variety of malignancies. Additional clinical trials are in development to formally evaluate MR-IGRT in the treatment of multiple disease sites with techniques such as SBRT and ART.

Frequency of GCH1 deletions in Dopa-responsive dystonia

We performed a systematic study on the frequency of point mutations and deletions of the gene GCH1 in dopa-responsive dystonia (DRD). A total of 136 dystonia patients were studied. Fifty of these had a sustained response to oral L-Dopa therapy (group 1: definite diagnosis of DRD), whereas the response to L-Dopa was incomplete or not tested in 86 patients (group 2: possible diagnosis of DRD). We found a GCH1 point mutation in 27 patients of group 1 (54%) and in four patients of group 2 (5%). Of these, nine single and one double mutation have not been described before. GCH1 deletions were detected in four patients of group 1 (8%) and in one patient of group 2 (1%). Among GCH1 point-mutation-negative patients with a definite diagnosis of DRD (group 1), the frequency of GCH1 deletions was 17% (4/23). We conclude that GCH1 deletion analysis should be incorporated into the routine molecular diagnosis of all patients with DRD with a sustained response to L-Dopa.

Distribution of two Asian-related coding SNPs in the MC1R and OCA2 genes

Very little is known about the genes and mechanisms affecting skin lightening in Asian populations. In this study, two coding SNPs, c.G1129A (R163Q) at the MC1R (melanocortin 1 receptor) gene and c.A1962G (H615R) at the OCA2 (oculocutaneous albinism type II) gene, were investigated in a total of 1,809 individuals in 16 populations from various areas. The Q163 and R615 alleles prevailed almost exclusively in East and Southeast Asian populations. Wright's F (ST) was 0.445 for R163Q and 0.385 for H615R among the 16 populations. The frequency of the Q163 allele was higher in Northeast Asians than in Southeast Asians. The frequency of the R615 allele was highest in South China and unlikely to be associated with levels of ultraviolet radiation. This allele may be a good marker to study the genetic affinity among East Asians because of its restricted distribution and marked difference in allele frequency.

Distribution of the F374 Allele of the SLC45A2 (MATP) Gene and Founder-Haplotype Analysis

The membrane-associated transporter protein (MATP) plays an important role in melanin synthesis. The L374F mutation in the SLC45A2 gene encoding MATP has been suggested to be associated with skin colour in major human populations. In this study more detailed distribution of the F374 allele was investigated in 1649 unrelated subjects from 13 Eurasian populations and one African population. The highest allele frequency was observed in Germans (0.965); French and Italians showed somewhat lower frequencies; and Turks had an intermediate value (0.615). Indians and Bangladeshis from South Asia were characterized by low frequencies (0.147 and 0.059, respectively). We also found the F374 allele in some East and Southeast Asian populations, and explained this by admixture. Haplotype analysis revealed that the haplotype diversity was much lower in Germans than in Japanese, and suggest that the L374F mutation occurred only once in the ancestry of Caucasians. The large differences in distribution of the F374 allele and its haplotypes suggest that this allele may be an important factor in hypopigmentation in Caucasian populations.

Characterization of genomic rearrangements of the alpha1-acid glycoprotein/orosomucoid gene in Ghanaians

In this study, the structure of the alpha1-acid glycoprotein (AGP), or orosomucoid (ORM), gene was investigated in a Ghanaian mother and her child, who shared an unusual variant, ORM1 S2(C), found by isoelectric focusing. Three remarkable changes of nucleotide sequence were observed: (1) The two ORM1 alleles, ORMI*S and ORMI*S2(C), had the AGP2 gene-specific sequence at one and three regions, respectively, in exon 5 to intron 5. The variant allele originating from ORMi*S was characterized by a G-to-A transition, resulting in an amino acid change from valine to methionine, which is also detected in ORM1 F2, a form that is common in Europeans. (2) The AGP2 gene of the child, inherited from the father, was duplicated, as revealed by long-range polymerase chain reaction. (3) Three new mutations were observed in two exons of the AGP2 genes of the mother and child. All of these novel genomic rearrangements, which were not observed in Japanese subjects, may have arisen through point mutation, gene conversion, and unequal crossover events. It is likely that the rearrangement of the AGP gene has often occurred in Africans.

Application of Y-chromosomal STR haplotypes to forensic genetics

This paper delivers population genetic data on Y-chromosomal short tandem repeat (STR) polymorphisms along with reports of unusual observations and casework. Population studies were carried out on the Y-specific STR polymorphisms DYS19, DYS385 I+II, DYS389 I+II, DYS390, DYS391, DYS392, and DYS393 in population samples from North India, Turkey, and Germany. In all three populations the vast majority of haplotypes was observed only once, especially in the Turkish group. Highly unusual cases are reported. In a German individual, we observed the variant allele DYS392*11.1, whereas a Turkish haplotype revealed a duplication at locus DYS19. Application of Y-chromosomal STR markers to forensic genetics was demonstrated in two cases: 1) a deficient paternity case, and 2) a father/son pair, where the Amelogenin primers failed to amplify the Y-homolog. In forensic genetics, Y-chromosomal STR polymorphisms are highly welcomed as an additional tool.

Online reference database of European Y-chromosomal short tandem repeat (STR) haplotypes

The reference database of highly informative Y-chromosomal short tandem repeat (STR) haplotypes (YHRD), available online at http://ystr.charite.de, represents the largest collection of male-specific genetic profiles currently available for European populations. By September 2000, YHRD contained 4688 9-locus (so-called "minimal") haplotypes, 40% of which have been extended further to include two additional loci. Establishment of YHRD has been facilitated by the joint efforts of 31 forensic and anthropological institutions. All contributing laboratories have agreed to standardize their Y-STR haplotyping protocols and to participate in a quality assurance exercise prior to the inclusion of any data. In view of its collaborative character, and in order to put YHRD to its intended use, viz. the support of forensic caseworkers in their routine decision-making process, the database has been made publicly available via the Internet in February 2000. Online searches for complete or partial Y-STR haplotypes from evidentiary or non-probative material can be performed on a non-commercial basis, and yield observed haplotype counts as well as extrapolated population frequency estimates. In addition, the YHRD website provides information about the quality control test, genotyping protocols, haplotype formats and informativity, population genetic analysis, literature references, and a list of contact addresses of the contributing laboratories.

Molecular analysis of the human orosomucoid gene ORM1*Q0köln responsible for incompatibility in a German paternity case

In a German paternity test, an alleged father was excluded only by reverse homozygosity of ORM1 phenotypes (mother ORM1 S, child ORM1 S and alleged father ORM1 F1) out of the 28 classical and DNA markers investigated. Without the ORM1 system the biostatistical probability of paternity was calculated to exceed 99.999%. The intensity of the immunoprinted bands of the ORM1 protein for the child and alleged father after isoelectric focusing appeared to be reduced to about half. To identify a possible null allele, gene-specific amplification followed by single-strand conformation polymorphism and sequencing analyses were carried out. Deletion of one of the two copies of a 4 bp direct repeat sequence (GTCT) in exon 4 of the consensus sequence of ORM1*F1 was observed in the child and alleged father. Thus, the sharing of a rare mutant gene, ORM1*Q0köln, increased the probability of paternity.

Sequence analysis and population data on the 'new' short tandem repeat locus D5S2360

We have studied the sequence structure and population genetics of a 'new' short tandem repeat polymorphism at locus D5S2360 in German Caucasians. Sequencing at this locus revealed a considerable variation, which is characterized by a tetranucleotide (AGAT)(n) repeat pattern with (GAT), (AGATT), and (AG) repeats dispersed throughout the alleles. These microvariations do not necessarily alter the size of the alleles. They may vary by one or two pairs or they may remain unchanged in size. At locus D5S2360 we observed 33 allelic lengths comprising at least 36 different alleles. Population data revealed a high polymorphism with a heterozygosity rate of approximately 92.5%.

A new method for the evaluation of matches in non-recombining genomes: application to Y-chromosomal short tandem repeat (STR) haplotypes in European males

A 9-locus microsatellite framework (minimal haplotype), previously developed for forensic purposes so as to facilitate stain analysis, personal identification and kinship testing, has been adopted for the establishment of a large reference database of male European Y-chromosomal haplotypes. The extent of population stratification pertaining to this database, an issue crucial for its practical forensic application, was assessed through analysis of molecular variance (AMOVA) of the 20 regional samples included. Despite the notion of some significant haplotype frequency differences, which were found to correlate with known demographic and historic features of Europeans, AMOVA generally revealed a high level of genetic homogeneity among the populations analyzed. Owing to their high diversity, however, accurate frequency estimation is difficult for Y-STR haplotypes when realistic (i.e. moderately sized) datasets are being used. As expected, strong pair-wise and higher order allelic associations were found to exist between all markers studied, implying that haplotype frequencies cannot be estimated as products of allele frequencies. A new extrapolation method was therefore developed which treats haplotype frequencies as random variables and generates estimates of the underlying distribution functions on the basis of closely related haplotypes. This approach, termed frequency 'surveying', is based upon standard population genetics theory and can in principle be applied to any combination of markers located on the Y-chromosome or in the mitochondrial genome. Application of the method to the quality assured reference Y-STR haplotype database described herein will prove very useful for the evaluation of positive trace-donor matches in forensic casework.

Human autosomal short tandem repeat types in Jat Sikhs from North India

This study provides Jat Sikhs population data in North India for nine short tandem repeat (STR) loci.

Characteristics and frequency of germline mutations at microsatellite loci from the human Y chromosome, as revealed by direct observation in father/son pairs

A number of applications of analysis of human Y-chromosome microsatellite loci to human evolution and forensic science require reliable estimates of the mutation rate and knowledge of the mutational mechanism. We therefore screened a total of 4,999 meioses from father/son pairs with confirmed paternity (probability >/=99. 9%) at 15 Y-chromosomal microsatellite loci and identified 14 mutations. The locus-specific mutation-rate estimates were 0-8. 58x10-3, and the average mutation rate estimates were 3.17x10-3 (95% confidence interval [CI] 1.89-4.94x10-3) across 8 tetranucleotide microsatellites and 2.80x10-3 (95% CI 1.72-4.27x10-3) across all 15 Y-chromosomal microsatellites studied. Our data show a mutational bias toward length increase, on the basis of observation of more repeat gains than losses (10:4). The data are in almost complete agreement with the stepwise-mutation model, with 13 single-repeat changes and 1 double-repeat change. Sequence analysis revealed that all mutations occurred in uninterrupted homogenous arrays of >/=11 repeats. We conclude that mutation rates and characteristics of human Y-chromosomal microsatellites are consistent with those of autosomal microsatellites. This indicates that the general mutational mechanism of microsatellites is independent of recombination.

Usefulness of conventional blood groups, DNA-minisatellites, and short tandem repeat polymorphisms in paternity testing: a comparison

A total of 215 paternity cases were analysed after testing 24 marker systems. Despite technical advantages of polymerase chain reaction related polymorphisms (automatisation, employment of robots, lesser requirements concerning of quality and quantity of DNA) it could be shown that the exclusive employment of a parentage testing kit is compromised by an increased risk of erroneous conclusions. It is estimated that in about 3-4% of the cases ambiguous situations have to be expected which are caused by the occurrence of single or double exclusions. In these cases it is impossible to decide whether the exclusions indicate either true nonpaternity or a de novo mutation. The situation might become even more complicated if an involvement of a close relative of the alleged father cannot be ruled out. We cautiously advance the hypothesis that in parentage testing DNA minisatellite polymorphisms from an optimal set of tools.

Human orosomucoid (ORM1) subtyping: further population genetic data and reports on the feasibility to type aged blood samples and stains

Genetic polymorphism of serum orosomucoid (ORM1) was investigated in 1072 unrelated German Caucasians using isoelectric focusing followed by Western blotting and EIA. The estimated allele frequencies were ORM1 *F1 = 0.5690, ORM1 *S = 0.3927, ORM1 *F2 = 0.0368, ORM1 *F2S = 0.0009 and ORM1 *F5 = 0.0005. The method was successfully applied to determine ORM1 phenotypes in aged blood samples and blood stains. The results indicated that the ORM protein is a informative and remarkably robust blood group system.

Specificity of head-up tilt testing in adolescents: effect of various degrees of tilt challenge in normal control subjects

OBJECTIVES

This study sought to determine the specificity of commonly used tilt protocols in children.

BACKGROUND

Tilt table testing is commonly utilized in the evaluation of children and adolescents with syncope despite a lack of uniformity in tilt protocols and a lack of studies of specificity in normal control subjects.

METHODS

Sixty-nine normal control volunteers (12 to 18 years old, 38 male, 31 female) with no previous history of syncope, presyncope or arrhythmia underwent tilting to 80 degrees, 70 degrees or 60 degrees for a maximum of 30 min on a motorized table with a footboard support. Autonomic maneuvers, including deep breathing, carotid massage, Valsalva maneuver and diving reflex, were performed before tilt testing to determine whether the response to these maneuvers could identify subjects prone to fainting during tilt testing.

RESULTS

Symptoms of presyncope and frank syncope were elicited in 24 of 69 subjects (13 male, 11 female): 6 (60%) of 10 were tilted at 80 degrees, 9 (29%) of 31 at 70 degrees and 9 (32%) of 28 at 60 degrees. Tilt testing at 80 degrees was terminated after the tenth subject by the institutional review board. The mean time to a positive test response was 10.5 min at 80 degrees, 14.2 min at 70 degrees and 13.2 min at 60 degrees. In the 80 degrees tilt, 4 of 10 subjects had a positive response within 10 minutes, whereas only 3 of 31 and 2 of 28 had a positive response within < 10 min at 70 degrees and 60 degrees tilt angles, respectively. Subjects with and without a positive response to tilt testing were similar with respect to age; gender; PR, QRS and QT intervals; and baseline heart rate and blood pressure. Likewise, responses to other autonomic function tests performed were similar in tilt-positive and tilt-negative patients. The power for detecting a significant difference between patients tilted at 80 degrees versus 60 degrees and 70 degrees was 0.45 and for detecting differences in autonomic tone between tilt-positive (n = 24) and tilt-negative (n = 45) subjects was 0.8.

CONCLUSIONS

Children appear to be more susceptible to orthostatic stress than adults. Therefore, tilt protocols commonly used in adults lack specificity in teenage patients. A specificity > 85% may be obtained by performing the tilt test at 60 degrees or 70 degrees for no longer than 10 min.

Population genetic and family data for the human minisatellite locus D16S309 (MS205) in Germans

The distribution of restriction fragments at the DNA minisatellite locus D16S309 was estimated by investigating blood samples from 2617 unrelated West German Caucasians and 1269 offspring. Furthermore segregation of fragments was studied in a large family and in trios. Altogether 2296 meioses were studied, revealing 7 paternal and 3 maternal mutations. Inspection of "phenotypes" did not reveal any remarkable deviation from Hardy-Weinberg equilibrium.