Phase I/II study of stereotactic body radiotherapy boost in patients with cervical cancer ineligible for intracavitary brachytherapy

PURPOSE

Stereotactic body radiotherapy (SBRT) boost is a promising treatment for cervical cancer patients who are ineligible for intracavitary brachytherapy (ICBT). The aim of this multicenter, single-arm, phase I/II study was to prospectively evaluate the efficacy and toxicity of SBRT boost.

MATERIALS AND METHODS

ICBT-ineligible patients with untreated cervical cancer were enrolled. Patients underwent whole-pelvic radiotherapy (45 Gy in 25 fractions) with SBRT boost to the primary lesion. In the phase I dose-escalation cohort (3 + 3 design), patients were treated with SBRT boost of 21 or 22.5 Gy in three fractions. Although dose-limiting toxicity was not confirmed, a dose of 21 Gy was selected for the phase II cohort because it was difficult to reproduce the pelvic organs position in two patients during the phase I trial. The primary endpoint was 2-year progression-free survival.

RESULTS

Twenty-one patients (phase I, n = 3; phase II, n = 18) were enrolled between April 2016 and October 2020; 17 (81%) had clinical stage III-IV (with para-aortic lymph node metastases) disease. The median (range) follow-up was 40 (10-84) months. The initial response was complete response in 20 patients and partial response in one patient. The 2-year locoregional control, progression-free survival, and overall survival rates were 84%, 67%, and 81%, respectively. Grade ≥ 3 toxicity was confirmed in one patient each in the acute (diarrhea) and late (urinary tract obstruction) phases.

CONCLUSION

These findings suggested that a SBRT boost is more effective than the conventional EBRT boost and can be an important treatment option for ICBT-ineligible patients with cervical cancer.

STUDY REGISTRATION

This study was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN000036845).

Single-shot fast cinematic imaging during merging process of multiple electron filaments in electrostatic potential well

For the first time, details of the spatial and temporal acceptable evolution of the merging process of co-rotating electron vortices in a potential well are successfully captured using a "single-shot method" with a high temporal resolution of 10 µs. Four-electron filaments are trapped inside the Beam eXperiment-Upgrade linear trap [H. Himura, Nucl. Instrum. Methods Phys. Res. A 811, 100 (2016)] with a uniform axial magnetic field and co-axial multi-ring electrodes. Images of non-emitting electron filaments are captured using a high-speed camera with up to 1 000 000 fps, a microchannel plate, a fast-decay phosphor screen of which fluorescence duration is 0.15 µs, and a super fine metallic mesh with an open area ratio of 89%. Images captured every 10 µs clearly show the growth of multiple short-wave instabilities in the wing trailing electron vortices. The experimental methods and measurement techniques presented in this paper can contribute to revealing exactly how small vortices evolve into a large structure or turbulence in a potential well through complex processes.

Dosimetric impact of MLC positional errors on dose distribution in IMRT

Optimizing the positional accuracy of multileaf collimators (MLC) for radiotherapy is important for dose accuracy and for reducing doses delivered to normal tissues. This study investigates dose sensitivity variations and complexity metrics of MLC positional error in volumetric modulated arc therapy and determines the acceptable ranges of MLC positional accuracy in several clinical situations. Treatment plans were generated for four treatment sites (prostate cancer, lung cancer, spinal, and brain metastases) using different treatment planning systems (TPSs) and fraction sizes. Each treatment plan introduced 0.25-2.0 mm systematic or random MLC leaf bank errors. The generalized equivalent uniform dose (gEUD) sensitivity and complexity metrics (MU/Gy and plan irregularity) were calculated, and the correlation coefficients were assessed. Furthermore, the required tolerances for MLC positional accuracy control were calculated. The gEUD sensitivity showed the highest dependence of systematic positional error on the treatment site, followed by TPS and fraction size. The gEUD sensitivities were 6.7, 4.5, 2.5, and 1.7%/mm for Monaco and 8.9, 6.2, 3.4, and 2.3%/mm (spinal metastasis, lung cancer, prostate cancer, and brain metastasis, respectively) for RayStation. The gEUD sensitivity was strongly correlated with the complexity metrics (r = 0.88-0.93). The minimum allowable positional error for MLC was 0.63, 0.34, 1.02, and 0.28 mm (prostate, lung, brain, and spinal metastasis, respectively). The acceptable range of MLC positional accuracy depends on the treatment site, and an appropriate tolerance should be set for each treatment site with reference to the complexity metric. It is expected to enable easier and more detailed MLC positional accuracy control than before by reducing dose errors to patients at the treatment planning stage and by controlling MLC quality based on complexity metrics, such as MU/Gy.

Antibacterial effect of Ag-containing hydroxyapatite thin film fabricated by sputtering

BACKGROUND

Infections related to joint prosthesis are still a major concern for orthopedic surgeons. Hydroxyapatite (HA) is a useful biocompatible material because of its good osteocompatibility. Antibacterial HA coatings have been fabricated with addition of antibacterial agents such as Ag to HA using the plasma spraying method. However, the plasma-sprayed HA coating suffers from fractures at large thicknesses. The sputter-coated HA thin film has a high density, and has been applied clinically for dental implants. However, there are no extensive studies on Ag-containing HA thin films.

OBJECTIVE

The aim of this study was to prepare an Ag-containing HA thin film by sputtering, and evaluate its antibacterial effect and cytotoxicity.

METHODS

The Ag-containing HA thin films were prepared by radio-frequency magnetron sputtering. The films were characterized using X-ray photoelectron spectroscopy, X-ray diffractometry, and scanning electron microscopy (SEM). The antibacterial activities and cytotoxicities of the films were also evaluated.

RESULTS

The Ag/Ca molar ratio of the films increased with the Ag ratio in the target. The SEM observation of the hydrothermally treated films showed surfaces covered with globular particles. All Ag-containing HA films exhibited an antibacterial effect against E. Coli. The number of cells of the films decreased with the Ag ratio. The films subjected to the hydrothermal treatment exhibited a higher number of cells than the as-sputtered films.

CONCLUSION

The Ag-containing HA thin film was effective in terms of antibacterial effect, and had a low cytotoxicity in the proliferation of osteoblast cells at a low Ag ratio in the target.

Erratum: Search for Cosmic-Ray Boosted Sub-GeV Dark Matter Using Recoil Protons at Super-Kamiokande [Phys. Rev. Lett. 130, 031802 (2023)]

This corrects the article DOI: 10.1103/PhysRevLett.130.031802.

Incidence and Prognostic Factors of Painful Vertebral Compression Fracture Caused by Spine Stereotactic Body Radiotherapy

PURPOSE/OBJECTIVE(S)

Most studies of vertebral compression fracture (VCF) caused by stereotactic body radiotherapy (SBRT) do not mention the symptoms. We aimed herein to determine the rate and prognostic factors of painful VCF caused by SBRT for spinal metastasis.

MATERIALS/METHODS

Between August 2013 and December 2021, spinal segments with VCF were retrospectively identified in patients treated with spine SBRT. Iatrogenic VCFs, excluding pathological fractures, were classified into a modified group and graded using CTCAE v5.0 as grade 1 (painless), grade 2 (mildly painful), or grade 3 (intensely painful, requiring hospitalization or surgery). The primary endpoint was the rate of painful VCF (grades 2-3). Moreover, various factors specific to the patient, tumor, and treatment were evaluated to determine their value in predicting the rate of painful VCF.

RESULTS

In total, 934 spinal segments in 387 patients were analyzed. The median follow-up after SBRT was 14 (range: 0-107) months. Sixty iatrogenic fractures (6.4%) comprising 31 de novo fractures and 29 existing VCF progressions were identified. The patients' median age was 68 (range: 38-79) years, and 31 (52%) spinal segments had a history of radiotherapy. Grade 1, 2, and 3 VCFs were confirmed in 41, four, and 15 segments, respectively. The rate of grade 3 VCF was 2.0% (19 / 934) of the spinal segments treated with SBRT. Eight (0.9%) VCFs required surgery for stabilization or decompression of spinal canal stenosis. None of the 17 VCFs treated with posterior decompression and fixation before SBRT developed into a painful VCF. On univariate analysis, the painful VCF rate was significantly higher in patients with no posterolateral tumor involvement than in those with bilateral or unilateral involvement (56.3% vs 22.7%; p = 0.026). Other spinal instability neoplastic score (SINS) components (Location, Pain, Bone lesion, Alignment, Vertebral body collapse), SINS (Stable/ Potentially unstable vs Unstable), age, number of spinal levels, radiation history, existing VCF, and interval between SBRT and VCF showed no significant correlation with painful VCF.

CONCLUSION

Although VCF is a known adverse effect of spine SBRT, 68% of the cases examined were painless (grade 1). Intensely painful VCFs (grade 3) were confirmed in only 1.6% of all the treated spinal segments. The absence of posterolateral tumor involvement was significantly associated with painful VCF.

Prospective Dosimetric Comparison Study Between Volumetric Modulated Arc Therapy and Intracavitary Brachytherapy for Cervical Cancer

PURPOSE/OBJECTIVE(S)

Although volumetric modulated arc therapy (VMAT) boost can achieve highly conformal dose distributions for cervical cancer, VMAT has the disadvantage of requiring set-up and organ motion margins. This study prospectively recruited patients with the cervical cancer and compared VMAT plan with intracavitary brachytherapy (ICBT) plan.

MATERIALS/METHODS

All patients treated with ICBT for locally advanced cervical cancer between April 2020 and September 2022 were enrolled. Patients had whole-pelvis radiotherapy, followed by CT scans with and without the tandem and ovoid in the same session (for the planning of ICBT and VMAT, respectively). ICBT planning characterizes the high-risk clinical target volume (HR-CTV) as the target volume and the bladder, rectum, sigmoid colon and small bowel loop as the organ at risk (OAR). VMAT planning defines the HR-CTV + 3 mm as the target volume and bladder, rectum + 3 mm (planning organ at risk volume (PRV) rectum), sigmoid colon + 3 mm (PRV sigmoid) and bowel bag as the OAR to account for set-up and organ motion. ICBT and VMAT plans were optimized for maximal dose received by at least 90% (D90%) of the target volume without impairing the dose constraints for the OARs. The prescribed dose (PD) was 26 Gy in 4 fractions. The dose constraints were determined as 25.2 Gy for D2 ml in the bladder and 20 Gy for D2 ml in the other OARs. The D90% and D100% of the target volume and D2 ml of OARs were compared between 2 plans using paired two-tailed Student's t test.

RESULTS

Seventeen patients were enrolled. Dose and volume parameters for the 2 plans are shown in Table 1. Of the 17 patients, D90% of the target volume received 100% PD in 4 cases with ICBT plans, in 6 cases for VMAT plans, and in 2 cases with both methods. For D90% of the target volume, ICBT plans were greater than VMAT plans in 4 cases, with a maximum difference of 5.6 Gy (ICBT: 26.0 Gy, SBRT: 20.4 Gy). VMAT plans were higher than ICBT plans in 11 cases, with a maximum difference of 10.3 Gy (ICBT: 14.5 Gy, SBRT: 24.8 Gy). The dose-limiting OARs to attain D90% of target volume were bladder in 12 cases and small bowel loop in 1 case for ICBT plans, while PRV rectum in 11 cases, PRV sigmoid in 4 cases and bowel bag in 1 case for VMAT plans.

CONCLUSION

This prospective study with 17 ICBT-eligible patients revealed D90% of the target volume demonstrated no substantial difference between VMAT and ICBT plans, while D100% showed a significant increase in VMAT plan compared to ICBT plan. Even with a set-up and organ motion margins on the HR-CTV and OARs, VMAT may have a dosimetric advantage over ICBT if the target geometry is complicated and close to the OARs.

Measurements of neutrino oscillation parameters from the T2K experiment using 3.6×1021 protons on target

The T2K experiment presents new measurements of neutrino oscillation parameters using 19.7 ( 16.3 ) × 10 20 protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional 4.7 × 10 20 POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on sin 2 θ 13 and the impact of priors on the δ CP measurement. Both analyses prefer the normal mass ordering and upper octant of sin 2 θ 23 with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on sin 2 θ 13 from reactors, sin 2 θ 23 = 0 . 561 - 0.032 + 0.021 using Feldman-Cousins corrected intervals, and Δ m 32 2 = 2 . 494 - 0.058 + 0.041 × 10 - 3 eV 2 using constant Δ χ 2 intervals. The CP-violating phase is constrained to δ CP = - 1 . 97 - 0.70 + 0.97 using Feldman-Cousins corrected intervals, and δ CP = 0 , π is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than 2 σ credible level using a flat prior in δ CP , and just below 2 σ using a flat prior in sin δ CP . When the external constraint on sin 2 θ 13 is removed, sin 2 θ 13 = 28 . 0 - 6.5 + 2.8 × 10 - 3 , in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.

Heterogeneous treatment effects of adjuvant therapy for patients with cervical cancer in the intermediate-risk group

BACKGROUND

The efficacy of adjuvant therapy for patients with cervical cancer with intermediate risk (CC-IR) remains controversial. We examined the impact of adjuvant therapy on survival outcomes in patients with CC-IR and evaluated the heterogeneous treatment effects (HTEs) of adjuvant therapies based on clinicopathologic characteristics.

METHODS

We retrospectively analyzed a previous Japanese nationwide cohort of 6192 patients with stage IB-IIB cervical cancer who underwent radical hysterectomy. We created two pairs of propensity score-matched treatment/control groups to investigate the treatment effects of adjuvant therapies: (1) adjuvant therapy versus non-adjuvant therapy; (2) chemotherapy versus radiotherapy conditional on adjuvant therapy. Multivariate analyses with treatment interactions were performed to evaluate the HTEs.

RESULTS

Among the 1613 patients with CC-IR, 619 and 994 were in the non-treatment and treatment groups, respectively. Survival outcomes did not differ between the two groups: 3-year progression-free survival (PFS) rates were 88.1% and 90.3% in the non-treatment and treatment groups, respectively (p = 0.199). Of the patients in the treatment group, 654 and 340 received radiotherapy and chemotherapy, respectively. Patients who received chemotherapy had better PFS than those who received radiotherapy (3-year PFS, 90.9% vs. 82.9%, p = 0.010). Tumor size was a significant factor that affected the treatment effects of chemotherapy; patients with large tumors gained better therapeutic effects from chemotherapy than those with small tumors.

CONCLUSION

Adjuvant therapy is optional for some patients with CC-IR; however, chemotherapy can be recommended as adjuvant therapy, particularly for patients with large tumors.

Evaluation of the MVCT-based radiomic features as prognostic factor in patients with head and neck squamous cell carcinoma

BACKGROUND

Megavoltage computed tomography (MVCT) images acquired during each radiotherapy session may be useful for delta radiomics. However, no studies have examined whether the MVCT-based radiomics has prognostic power. Therefore, the purpose of this study was to examine the prognostic power of the MVCT-based radiomics for head and neck squamous cell carcinoma (HNSCC) patients.

METHODS

100 HNSCC patients who received definitive radiotherapy were analyzed and divided into two groups: training (n = 70) and test (n = 30) sets. MVCT images obtained using TomoTherapy for the first fraction of radiotherapy and planning kilovoltage CT (kVCT) images obtained using Aquilion LB CT scanner were analyzed. Primary gross tumor volume (GTV) was propagated from kVCT to MVCT images using rigid registration, and 107 radiomic features were extracted from the GTV in MVCT and kVCT images. Least absolute shrinkage and selection operator (LASSO) Cox regression model was used to examine the association between overall survival (OS) and rad score calculated for each patient by weighting the feature value through the coefficient when features were selected. Then, the predictive values of MVCT-based and kVCT-based rad score and patient-, treatment-, and tumor-specific factors were evaluated.

RESULTS

C-indices of the rad score for MVCT- and kVCT-based radiomics were 0.667 and 0.685, respectively. The C-indices of 6 clinical factors were 0.538-0.622. The 3-year OS was significantly different between high- and low-risk groups according to the MVCT-based rad score (50% vs. 83%; p < 0.01).

CONCLUSIONS

Our results suggested that MVCT-based radiomics had stronger prognostic power than any single clinical factor and was a useful prognostic factor when predicting OS in HNSCC patients.

Experimental investigation of the effective point of measurement for plane-parallel chambers used in electron beam dosimetry

In this study, the effective point of measurement (EPOM) for plane-parallel ionization chambers in clinical high-energy electron beams was determined experimentally. Previous studies have reported that the EPOM of plane-parallel chambers is shifted several tens of millimeters downstream from the inner surface of the entrance window to the cavity. These findings were based on the Monte Carlo (MC) simulation, and few experimental studies have been performed. Thus, additional experimental validations of the reported EPOMs were required. In this study, we investigated the EPOMs of three plane-parallel chambers (NACP-02, Roos and Advanced Markus) for clinical electron beams. The EPOMs were determined by comparing the measured percentage depth-dose (PDD) of the plane-parallel chambers and the PDD obtained using the microDiamond detector. The optimal shift to the EPOM was energy-dependent. The determined EPOM showed no chamber-to-chamber variation, thereby allowing the use of a single value. The mean optimal shifts were 0.104 ± 0.011, 0.040 ± 0.012, and 0.012 ± 0.009 cm for NACP-02, Roos, and Advanced Markus, respectively. These values are valid in the R₅₀ range from 2.40 to 8.82 cm, which correspond to 6-22 MeV. Roos and Advanced Markus exhibited similar results to those of the previous studies, but NACP-02 showed a larger shift. This is probably due to the uncertainty of the entrance window of NACP-02. Therefore, it is necessary to carefully consider where the optimal EPOM is located when using this chamber.

Clinical impact of radiation-induced myocardial damage detected by cardiac magnetic resonance imaging and dose-volume histogram parameters of the left ventricle as prognostic factors of cardiac events after chemoradiotherapy for esophageal cancer

This prospective study aimed to evaluate whether radiation (RT)-induced myocardial damage by cardiac magnetic resonance (CMR) imaging could be a predictor of cardiac events after chemoradiotherapy (CRT) for esophageal cancer and determine the dose-volume histogram (DVH) parameters of the left ventricle (LV) in predicting cardiac events. CMR imaging was performed before and 6 months after CRT in patients receiving definitive CRT. RT-induced myocardial damage was defined as abnormal CMR findings indicating myocardial fibrosis corresponding to an isodose line of ≥30 Gy. The cutoff values of the LV DVH parameters were calculated using the receiver operating characteristic curve based on the presence of RT-induced myocardial damage. The prognostic factors related to cardiac events of Grade 3 or higher were examined. Twenty-three patients were enrolled in the study. RT-induced myocardial damage by late gadolinium enhancement and/or an increase of 100 ms or higher in native T1 post-CRT was detected in 10 of the 23 patients. LV V45 was the best predictive factor for RT-induced myocardial damage with a cutoff value of 2.1% and an area under the curve of 0.75. The median follow-up period was 82.1 months. The 5- and 7-year cumulative incidences of cardiac events of Grade 3 or higher were 14.7 and 22.4%, respectively. RT-induced myocardial damage and LV V45 were significant risk factors (P = 0.015 and P = 0.013, respectively). RT-induced myocardial damage is a significant predictor of cardiac events. LV V45 is associated with RT-induced myocardial damage and subsequent cardiac events.

Incidence and Prognostic Factors of Painful Vertebral Compression Fracture Caused by Spine Stereotactic Body Radiotherapy

Most studies of vertebral compression fractures (VCF) caused by stereotactic body radiotherapy (SBRT) do not discuss the symptoms of this complication. In this paper, we aimed to determine the rate and prognostic factors of painful VCF caused by SBRT for spinal metastases. Spinal segments with VCF in patients treated with spine SBRT between 2013 and 2021 were retrospectively reviewed. The primary endpoint was the rate of painful VCF (grades 2-3). Patient demographic and clinical characteristics were evaluated as prognosticators. In total, 779 spinal segments in 391 patients were analyzed. The median follow-up after SBRT was 18 (range: 1-107) months. Sixty iatrogenic VCFs (7.7%) were identified. The rate of painful VCF was 2.4% (19/779). Eight (1.0%) VCFs required surgery for internal fixation or spinal canal decompression. The painful VCF rate was significantly higher in patients with no posterolateral tumor involvement than in those with bilateral or unilateral involvement (50% vs. 23%; p = 0.042); it was also higher in patients with spine without fixation than in those with fixation (44% vs. 0%; p < 0.001). Painful VCFs were confirmed in only 2.4% of all the irradiated spinal segments. The absence of posterolateral tumor involvement and no fixation was significantly associated with painful VCF.

Collective excitations in a melt of fast phase change material GeCu2Te3

Inelastic x-ray scattering measurements have been carried out to investigate atomic dynamics in a melt of fast phase change material GeCu₂Te₃. The dynamic structure factor was analysed using the model function with three damped harmonic oscillator components. By investigating the correlation between the excitation energy and the linewidth, and that between the excitation energy and the intensity on contour maps of a relative approximate probability distribution function proportional toexp(-χ2/N), we could judge the reliability of each inelastic excitation in the dynamic structure factor. The results indicate that there are two inelastic excitation modes besides the longitudinal acoustic one in the liquid. The lower energy excitation could be assigned to the transverse acoustic one whereas the higher energy one disperses like fast sound. The latter result may imply that the liquid ternary alloy exhibits a microscopic phase separation tendency.

Accelerated hypofractionated radiotherapy with 3 Gy per fraction for central/ultra-central lung tumors: toxicity to mediastinal organs

BACKGROUND

Accelerated hypofractionated radiotherapy with 3 Gy per fraction is routinely performed for central lung tumors in Japan. However, the tolerable doses to mediastinal organs at risk during this procedure are unclear. This study aimed to clarify the rate of toxicities and tolerable doses to mediastinal organs.

METHODS

Patients treated with accelerated hypofractionated radiotherapy using a total dose of 60-75 Gy, with 3 Gy per fraction, for central lung tumors (July 2009-April 2021) were retrospectively reviewed. We extracted patients who received ≥30 Gy irradiation to each mediastinal organ and analyzed dosimetric factors, including doses to 0.03, 0.5, 1, 4 and 10 mL of each organ, in relation to grade 3-5 toxicities, except for radiation pneumonitis.

RESULTS

In total, 251 organs in 91 (ultra-central, 24) lesions were analyzed, with a median follow-up duration of 26 months (range, 4-94). The prescribed doses were 75/72/69/66/63/60 Gy for 52/14/16/3/2/4 lesions, respectively. Grade 3 bronchopulmonary hemorrhage was confirmed in two (2.2%) patients, whose tumors were located ultra-centrally. The two patients with toxicity received up to 74.5 and 71.6 Gy to the bronchus. Among patients who received 70 Gy or more to the bronchus, the incidence rate was 7% (2/28 patients).

CONCLUSION

The rate of severe toxicities was low (2.2%). Although we did not identify the dose tolerance of the organs, because of the low incidence rate, we did note that doses of >70 Gy to the bronchus were likely to cause bronchopulmonary hemorrhage.

Impact of CT scan parameters on deformable image registration accuracy using deformable thorax phantom

The purpose of this study was to evaluate the deformable image registration (DIR) accuracy using various CT scan parameters with deformable thorax phantom. Our developed deformable thorax phantom (Dephan, Chiyoda Technol Corp, Tokyo, Japan) was used. The phantom consists of a base phantom, an inner phantom, and a motor-derived piston. The base phantom is an acrylic cylinder phantom with a diameter of 180 mm, which simulates the chest wall. The inner phantom consists of deformable, 20 mm thick disk-shaped sponges with 48 Lucite beads and 48 nylon cross-wires which simulate the vascular and bronchial bifurcations of the lung. Peak-exhale and peak-inhale images of the deformable phantom were acquired using a CT scanner (Aquilion LB, TOSHIBA). To evaluate the impact of CT scan parameters on DIR accuracy, we used the four tube voltages (80, 100, 120, and 135 kV) and six reconstruction algorithms (FC11, FC13, FC15, FC41, FC44, and FC52). Intensity-based DIR was performed between the two images using MIM Maestro (MIM software, Cleveland, USA). Fiducial markers (beads and cross-wires) based target registration error (TRE) was used for quantitative evaluation of DIR. In case with different tube voltages, the range of average TRE were 4.44-5.69 mm (reconstruction algorithm: FC13). In case with different reconstruction algorithms, the range of average TRE were 4.26-4.59 mm (tube voltage: 120 kV). The TRE were differed by up to 3.0 mm (3.96-6.96 mm) depending on the combination of tube voltage and reconstruction algorithm. Our result indicated that CT scan parameters had moderate impact of TRE, especially for reconstruction algorithms for the deformable thorax phantom.

Multicenter registry of the Watchman left atrial appendage closure device for patients with atrial fibrillation in Japan: The TERMINATOR registry

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Boston Scientific Japan

Background

Transcatheter left atrial appendage closure (LAAC) provides an alternative to oral anticoagulation for thromboembolic risk reduction in patients with nonvalvular atrial fibrillation (AF). A meta-analysis of previous two randomized trials reported improved rates of hemorrhagic stroke, cardiovascular/unexplained death, and nonprocedural bleeding compared to warfarin (1). Recently, the next-generation LAAC device, the Watchman FLX system, became available, and showed a low incidence of adverse events and a high incidence of anatomic closure (2). This transcatheter stroke prevention has already been approved in Asian countries. However, there is little data of LAAC in Asian population.

Purpose

This study sought to assess efficacy and safety of LAAC for patients with nonvalvular AF in Asia.

Methods

The TERMINATOR (Transcatheter Modification of Left Atrial Appendage by Obliteration with Device) registry is a multicenter nonrandomized study in Japan. This enrolled patients who underwent LAAC in 23 Japanese institutions. The LAAC was indicated for patients with nonvalvular atrial fibrillation in whom oral anticoagulation is required, but who have a risk of bleeding (history of BARC type 3 bleeding or HAS-BLED score ≥3 points). Baseline patient and procedural characteristics and clinical outcomes were evaluated.

Results

A total of 729 patients were enrolled between September 2019 and November 2021. The mean age was 74.9±8.8 years and the mean CHA2DS2-VASc score was 4.7±1.5. The Watchman generation 2.5 and FLX system were used in 469 (64.3%) and 260 patients (35.7%), respectively. Procedural success was achieved in 722 patients (99.0%). In-hospital adverse events were as follows; 6 tamponades (0.8%), 3 pericardial effusion (0.4%), 2 device embolization (0.3%), no stroke (0%), and no death (0%). During follow-up, device-related thrombus and all-cause death were reported in 16 (2.2%) and 23 patients (3.2%), respectively.

Conclusions

LAAC with the Watchman system provides compatible efficacy and safety outcomes in Asian population.

Search for Cosmic-Ray Boosted Sub-GeV Dark Matter Using Recoil Protons at Super-Kamiokande

We report a search for cosmic-ray boosted dark matter with protons using the 0.37  megaton×years data collected at Super-Kamiokande experiment during the 1996-2018 period (SKI-IV phase). We searched for an excess of proton recoils above the atmospheric neutrino background from the vicinity of the Galactic Center. No such excess is observed, and limits are calculated for two reference models of dark matter with either a constant interaction cross section or through a scalar mediator. This is the first experimental search for boosted dark matter with hadrons using directional information. The results present the most stringent limits on cosmic-ray boosted dark matter and exclude the dark matter-nucleon elastic scattering cross section between 10^{-33}cm^{2} and 10^{-27}cm^{2} for dark matter mass from 1  MeV/c^{2} to 300  MeV/c^{2}.

Radiation pneumonitis prediction model with integrating multiple dose-function features on 4DCT ventilation images

PURPOSE

Radiation pneumonitis (RP) is dose-limiting toxicity for non-small-cell cancer (NSCLC). This study developed an RP prediction model by integrating dose-function features from computed four-dimensional computed tomography (4DCT) ventilation using the least absolute shrinkage and selection operator (LASSO).

METHODS

Between 2013 and 2020, 126 NSCLC patients were included in this study who underwent a 4DCT scan to calculate ventilation images. We computed two sets of candidate dose-function features from (1) the percentage volume receiving > 20 Gy or the mean dose on the functioning zones determined with the lower cutoff percentile ventilation value, (2) the functioning zones determined with lower and upper cutoff percentile ventilation value using 4DCT ventilation images. An RP prediction model was developed by LASSO while simultaneously determining the regression coefficient and feature selection through fivefold cross-validation.

RESULTS

We found 39.3 % of our patients had a ≥ grade 2 RP. The mean area under the curve (AUC) values for the developed models using clinical, dose-volume, and dose-function features with a lower cutoff were 0.791, and the mean AUC values with lower and upper cutoffs were 0.814. The relative regression coefficient (RRC) on dose-function features with upper and lower cutoffs revealed a relative impact of dose to each functioning zone to RP. RRCs were 0.52 for the mean dose on the functioning zone, with top 20 % of all functioning zone was two times greater than that of 0.19 for these with 60 %-80 % and 0.17 with 40 %-60 % (P < 0.01).

CONCLUSIONS

The introduction of dose-function features computed from functioning zones with lower and upper cutoffs in a machine learning framework can improve RP prediction. The RRC given by LASSO using dose-function features allows for the quantification of the RP impact of dose on each functioning zones and having the potential to support treatment planning on functional image-guided radiotherapy.

Risk of radiculopathy caused by second course of spine stereotactic body radiotherapy

Objective

Stereotactic body radiotherapy is used to treat spinal metastases; however, 10% of patients experience local failure. We aimed to clarify the outcomes of the second course of stereotactic body radiotherapy for spinal metastases with a uniform fractionation schedule at our institution.

Methods

Data of patients treated with a second salvage stereotactic body radiotherapy course at the same spinal level or adjacent level from July 2018 to December 2020 were retrospectively reviewed. The initial prescribed dose was 24 Gy in two fractions, and the second dose 30 or 35 Gy in five fractions. The spinal cord dose constraint at the second course was 15.5 Gy at the maximum point dose. The endpoints were local failure and adverse effects. Local failure was defined as tumor progression using imaging.

Results

We assessed 19 lesions in 17 patients, with radioresistant lesions in 14 (74%) cases, the second stereotactic body radiotherapy to the same/adjacent spinal level in 13/6 cases, the median interval between stereotactic body radiotherapy of 23 (range, 6–52) months, and lesions compressing the cord in 5 (26%) cases. The median follow-up period was 19 months. The 12- and 18-month local failure rates were 0% and 8%, respectively. Radiation-induced myelopathy, radiculopathy and vertebral compression fractures were observed in 0 (0%), 4 (21%) and 2 (11%) lesions, respectively. Three patients with radiculopathy experienced almost complete upper or lower limb paralysis.

Conclusions

The second course of salvage stereotactic body radiotherapy for spinal metastases achieved good local control with a reduced risk of myelopathy. However, a high occurrence rate of radiation-induced radiculopathy has been confirmed.

Stereotactic body radiotherapy for spinal oligometastases: a review on patient selection and the optimal methodology

Stereotactic body radiotherapy (SBRT) has excellent local control and low toxicity for spinal metastases and is widely performed for spinal oligometastases. However, its additional survival benefit to standard of care, including systemic therapy, is unknown because the results of large-scale randomized controlled trials regarding SBRT for oligometastases have not been reported. Consequently, the optimal patient population among those with spinal oligometastases and the optimal methodology for spine SBRT remain unclear. The present review article discusses two topics: evidence-based optimal patient selection and methodology. The following have been reported to be good prognostic factors: young age, good performance status, slow-growing disease with a long disease-free interval, minimal disease burden, and mild fluorodeoxyglucose accumulation in positron emission tomography. In addition, we proposed four measures as the optimal SBRT method for achieving excellent local control: (i) required target delineation; (ii) recommended dose fraction schedule (20 or 24 Gy in a single fraction for spinal oligometastases and 35 Gy in five fractions for lesions located near the spinal cord); (iii) optimizing dose distribution for the target; (iv) dose constraint options for the spinal cord.

Local control of stereotactic body radiotherapy with dynamic tumor tracking for lung tumors: a propensity score-matched analysis

Background

Dynamic tumor tracking (DTT) is a method of respiratory motion management in radiotherapy. It reduces the radiation field but risks delivering an insufficient radiation dose to the tumor. We investigated the local control of DTT-stereotactic body radiotherapy (SBRT) for lung tumors.

Methods

Patients treated with SBRT for early-stage, non-small-cell lung cancer and lung metastases (2013–18) were retrospectively reviewed. Patients with tumor motion &gt;1 cm were treated with DTT-SBRT (DTT group); those with tumor motion ≤1 cm were treated with static-SBRT (static group). A static planning target volume for the static-SBRT plan was also created for patients in the DTT group, and planning target volume reduction relative to the planning target volume for the DTT-SBRT plan was assessed. Patients were matched in a 1:1 ratio using a propensity score predictive of the SBRT technique.

Results

Of the 245 lesions in 218 patients (median follow-up, 25.4 months), 69 were treated with DTT-SBRT and 176 with static-SBRT. The median planning target volume reduction in the DTT group was 30.3%. After propensity score matching, 124 lesions were included (62 per group). Two-year local control rates for the DTT and static groups were 94.2 and 95.9%, respectively, for all lesions (P = 0.19) and 96.3 and 94.5%, respectively, for matched lesions (P = 0.79). In univariate analysis, DTT-SBRT was not associated with local control for all lesions (hazard ratio, 2.06; P = 0.20) or matched lesions (hazard ratio, 1.22; P = 0.79). No grade 4/5 toxicities were observed.

Conclusions

DTT-SBRT for lung tumors reduced the planning target volume, but not local control rates. DTT was useful for respiratory motion management.

Prediction of radiation pneumonitis with machine learning using 4D-CT based dose-function features

In this article, we highlight the fundamental importance of the simultaneous use of dose-volume histogram (DVH) and dose-function histogram (DFH) features based on functional images calculated from 4-dimensional computed tomography (4D-CT) and deformable image registration (DIR) in developing a multivariate radiation pneumonitis (RP) prediction model. The patient characteristics, DVH features and DFH features were calculated from functional images by Hounsfield unit (HU) and Jacobian metrics, for an RP grade ≥ 2 multivariate prediction models were computed from 85 non-small cell lung cancer patients. The prediction model is developed using machine learning via a kernel-based support vector machine (SVM) machine. In the patient cohort, 21 of the 85 patients (24.7%) presented with RP grade ≥ 2. The median area under curve (AUC) was 0.58 for the generated 50 prediction models with patient clinical features and DVH features. When HU metric and Jacobian metric DFH features were added, the AUC improved to 0.73 and 0.68, respectively. We conclude that predictive RP models that incorporate DFH features were successfully developed via kernel-based SVM. These results demonstrate that effectiveness of the simultaneous use of DVH features and DFH features calculated from 4D-CT and DIR on functional image-guided radiotherapy.

Fracture risk following stereotactic body radiotherapy for long bone metastases

BACKGROUND

Stereotactic body radiotherapy is a new treatment modality for long bone metastasis and has not been discussed in literature. We aimed to clarify stereotactic body radiotherapy outcomes for long bone metastases.

METHODS

Data of patients receiving stereotactic body radiotherapy for long bone metastases (July 2016-November 2020) were retrospectively reviewed. The prescribed dose was 30 or 35 Gy in five fractions. The endpoints were local failure and adverse effects. Local failure was defined as radiological tumor growth within the irradiation field. Adverse effects were evaluated according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.

RESULTS

Nineteen osseous lesions in 17 patients were assessed. The target lesions included 13 femoral, 4 humeral and 2 radial lesions. The median follow-up duration was 14 (range, 3-62) months. The 12- and 18-month local failure rates were 0 and 11%, respectively. Following 2 and 46 months of stereotactic body radiotherapy, two lesions (11%) resulted in painful femoral fractures (grade 3). Both patients underwent bipolar hip arthroplasty and could walk normally after surgery. In the late phase, one patient developed radiculopathy (almost complete paralysis of grasp) and another developed grade 2 limb edema. Other grade 2 or more severe acute and late toxicities were not observed during the follow-up period.

CONCLUSIONS

Stereotactic body radiotherapy for long bone metastases achieved excellent local control and caused two femoral fractures. We argue that stereotactic body radiotherapy for curative intent should not be contraindicated in long bone oligometastasis because fractures do not directly contribute to life expectancy.

Low energy excitation in liquid Sb and liquid Bi observed in inelastic x-ray scattering spectra

The dynamic structure factorS(Q,E), whereQandEare momentum and energy transfer, respectively, has been measured for liquid Sb, using inelastic x-ray scattering. A modified damped harmonic oscillator model function was applied to analyseS(Q,E) of liquid Sb and also to that of liquid Bi by Inuiet al(2015Phys. Rev.B92, 054206). The obtained excitation energy was in fairly good agreement with that predicted byab initiomolecular dynamics simulations on these liquid semi-metals. The excitation energy of the longitudinal acoustic mode in liquid Sb and liquid Bi exhibits flat-toppedQdependence whereas the lower excitation energy below the longitudinal acoustic excitation showsQ-gap behaviour. From the viscosity estimated from theQ-gap experimentally obtained, it is inferred that the lower energy excitation arises from the transverse acoustic excitation in the liquids.

Developmental potential of cryopreserved gonadal germ cells from 7-day-old chick embryos recovered using the PBS(-) method

1. A series of experiments were conducted to examine the developmental potential of cryopreserved gonadal germ cells (GGCs) recovered from both males and females on embryo day 7 (7 d-GGCs) using the PBS(-) method. Germline chimeras were produced by transferring 200 frozen/unfrozen 7 d-GGCs recovered from female/male Rhode Island Red (RIR) embryos into the dorsal aorta of 2-day-old female and male white leghorn (WL) embryos.2. Germ-cell recipient embryos were hatched and raised to sexual maturity and progeny testing was conducted by mating with RIR of the opposite sex. Brown-feathered progeny chicks were hatched in all eight possible progeny testing combinations, except for male GGC recipients produced by transferring female GGCs. Furthermore, brown-feathered progeny chicks were hatched when frozen-thawed sperm from male germline chimeras, produced by transferring unfrozen 7d-GGCs, were inseminated in normal female RIR and female WL germline chimeras.3. The results indicated that cryopreserved female/male GGCs from 7-day-old chick embryos, recovered using the PBS(-) method, were fully capable of developing into normal spermatozoa and ova in the gonad of recipient embryos under appropriate GGC donor/recipient combinations.

Phase II clinical trial of separation surgery followed by stereotactic body radiotherapy for metastatic epidural spinal cord compression

BACKGROUND

Stereotactic body radiotherapy (SBRT) is a postoperative treatment option for spinal metastases. As data on surgery with SBRT are limited to retrospective studies, this single-center, single-arm, phase II study aimed to prospectively evaluate the outcomes of separation surgery and SBRT for metastatic epidural spinal cord compression (MESCC).

METHODS

Patients with symptomatic MESCC due to a solid carcinoma were enrolled. The protocol for treatments comprised preoperative embolization, separation surgery, and spine SBRT. Surgical procedures were performed via the posterior approach, with decompression and a fixation procedure. The prescribed dose for spine SBRT was 24 Gy in two fractions. The primary endpoint was the 12-month local failure (LF) rate. The secondary endpoints were ambulatory functions and adverse effects.

RESULTS

Thirty-three patients were registered between November 2017 and October 2019. All patients satisfied the inclusion criteria, and all but one completed the protocol treatment. Twenty-three patients (70%) had radioresistant lesions. The Bilsky grade at registration was 1c, 2, and 3 in 4, 8, and 21 patients, respectively. The median follow-up duration after registration was 15 (range 3-35) months. Three months after the administration of treatments according to the protocol, 90% of the patients (26/29) had diseases of Bilsky grade ≤ 1. The 12-month LF rate was 13%. Twenty patients could walk normally or with a cane 12 months after registration. Radiation-induced myelopathy, radiculopathy, and vertebral compression fracture were observed in zero, one, and six patients, respectively.

CONCLUSIONS

Separation surgery with SBRT for MESCC was effective in decompression and long-term local control. These findings warrant larger randomized controlled trials to compare SBRT with conventional radiotherapy.

Development of a physical geometric phantom for deformable image registration credentialing of radiotherapy centers for a clinical trial

PURPOSE

This study aimed to develop a physical geometric phantom for the deformable image registration (DIR) credentialing of radiotherapy centers for a clinical trial and tested the feasibility of the proposed phantom at multiple domestic and international institutions.

METHODS AND MATERIALS

The phantom reproduced tumor shrinkage, rectum shape change, and body shrinkage using several physical phantoms with custom inserts. We tested the feasibility of the proposed phantom using 5 DIR patterns at 17 domestic and 2 international institutions (21 datasets). Eight institutions used the MIM software (MIM Software Inc, Cleveland, OH); seven used Velocity (Varian Medical Systems, Palo Alto, CA), and six used RayStation (RaySearch Laboratories, Stockholm, Sweden). The DIR accuracy was evaluated using the Dice similarity coefficient (DSC) and Hausdorff distance (HD).

RESULTS

The mean and one standard deviation (SD) values (range) of DSC were 0.909 ± 0.088 (0.434-0.984) and 0.909 ± 0.048 (0.726-0.972) for tumor and rectum proxies, respectively. The mean and one SD values (range) of the HD value were 5.02 ± 3.32 (1.53-20.35) and 5.79 ± 3.47 (1.22-21.48) (mm) for the tumor and rectum proxies, respectively. In three patterns evaluating the DIR accuracy within the entire phantom, 61.9% of the data had more than a DSC of 0.8 in both tumor and rectum proxies. In two patterns evaluating the DIR accuracy by focusing on tumor and rectum proxies, all data had more than a DSC of 0.8 in both tumor and rectum proxies.

CONCLUSIONS

The wide range of DIR performance highlights the importance of optimizing the DIR process. Thus, the proposed method has considerable potential as an evaluation tool for DIR credentialing and quality assurance.

[Quality Assurance of Bone SBRT]

Stereotactic body radiation therapy (SBRT) is a high-precision radiation therapy technique that enables to deliver a high ablative biological dose in 1 to 5 high dose-fractions despite sparing the high dose of adjacent organs at risk. SBRT has emerged as an alternative to conventional radiation therapy for spinal metastases and has been applied to patients with non-spine bone metastases as well. Since bone SBRT is the technique of high biologically effective dose to the local lesion, quality assurance (QA) of the entire treatment process is an essential for performing SBRT. This report provides QA procedures for performing bone SBRT.

Efficacy and toxicity of re-irradiation spine stereotactic body radiotherapy with respect to irradiation dose history

OBJECTIVE

We aimed to clarify the outcomes of re-irradiation stereotactic body radiotherapy for spinal metastases with a uniform dose fractionation schedule at our institution.

METHODS

Data of patients treated with re-irradiation stereotactic body radiotherapy for spinal metastases (September 2013-March 2020) were retrospectively reviewed. The prescribed dose was 24 Gy in two fractions. The spinal cord dose constraint and dose for previously irradiated cases ≥50 Gy in 25 fractions were 12.2 Gy (maximum dose) and 11 Gy, respectively. The endpoints were pain control, local failure and adverse effects. Pain status was measured on a scale of 0-10 using the patients' self-reports and pain response was defined using international consensus criteria. Local failure was defined as tumor progression on imaging evaluations.

RESULTS

We assessed 133 lesions in 123 patients, where 70 (52.6%) had three or more spinal levels treated, 58 (43.6%) had previous irradiation doses of 40 Gy or more and 53 (39.8%) had the targets compressing the cord. The median follow-up was 12 months and the 3-, 6- and 12-month pain response rate was 75, 64 and 59%, respectively. The 1-year local failure rate was 25.8%. Previous irradiation dose was not correlated with local failure rate (P = 0.13). Radiation-induced myelopathy, radiculopathy and vertebral compression fractures were observed in 4 (3.0%), 2 (1.5%) and 17 (13.8%) lesions, respectively. A trend towards an association between any toxicity and previous irradiation dose was not observed.

CONCLUSIONS

Re-irradiation spine stereotactic body radiotherapy achieved good local control and pain control, with reduced risk of radiation myelopathy.

High neutrophil-to-lymphocyte ratio is a predictor of short-term survival for patients with recurrent cervical cancer after radiation-based therapy

AIM

Patients with recurrent cervical cancer after radiotherapy have poor prognoses because of the lack of effective treatment options. Biomarkers to predict survival outcomes for recurrent cervical cancer are warranted because patients with limited life expectancy sometimes benefit from less aggressive treatment in combination with early palliative care. Therefore, we aimed to explore a predictive biomarker for the outcomes of patients with recurrent cervical cancer.

METHODS

We retrospectively investigated 231 patients initially treated with radiation-based therapy between January 2004 and December 2015. The associations between clinicopathological features at the time of relapse and overall survival after relapse were assessed. As factors which reflect patients' conditions, we particularly focused on C-reactive protein-to-albumin ratio (CAR) and neutrophil-to-lymphocyte ratio (NLR) at the time of relapse. Additionally, we investigated biomarkers predictive of short-term survival.

RESULTS

Among 231 patients, 91 patients experienced relapse and 74 patients died during the follow-up period. Multivariate analysis revealed that treatment after relapse, CAR, and NLR was significantly associated with overall survival. Among them, treatment after relapse significantly affected survival outcomes, and patients who received definitive local treatment had a better 3-year survival rate than those who received other treatments. Conversely, NLR was the most influential biomarker for short-term survival, and the prognosis of patients with high NLRs was much worse than those with low NLRs.

CONCLUSIONS

This study thus demonstrated that, for the patients with recurrent cervical cancer who received radiation-based therapy, definitive local treatment can provide long-term survival and extremely high NLRs are predictive of short-term survival.

Stereotactic body radiotherapy for bone metastases in patients with colorectal cancer

OBJECTIVE

To clarify the clinical outcomes of stereotactic body radiotherapy for colorectal cancer-derived bone metastases and identify factors predicting treatment failure.

METHODS

Patients treated with stereotactic body radiotherapy for bone metastases from colorectal cancer between September 2013 and June 2019 were retrospectively reviewed. The prescribed dose for spine and non-spine bone metastases was 24 Gy in two fractions and 35 Gy in five fractions, respectively. The end point was local failure, which was defined as tumour progression on imaging evaluations. In addition, various treatment- and tumour-specific factors were evaluated to determine predictors of local failure.

RESULTS

This study included 43 lesions in 38 patients, with solitary bone metastases in 18 lesions (42%), re-irradiation stereotactic body radiotherapy in 28 lesions (65%) and postoperative stereotactic body radiotherapy due to spinal cord compression in 10 lesions (23%). The median follow-up after stereotactic body radiotherapy was 12 (range, 2-60) months. The 1-year LF rate was 44%. In the univariate analysis, sacral metastases (P = 0.02) were found to be significantly correlated with LF, and multiple-course systemic therapy before stereotactic body radiotherapy (P= 0.06) and large target volume (P = 0.07) showed a trend towards an association with LF. However, these factors were not independent predictors of LF in the multivariate analysis.

CONCLUSION

More than 40% of the lesions treated with stereotactic body radiotherapy for bone metastases from colorectal cancer showed LF within 1 year. No poor prognostic factors could be identified statistically. The poor outcomes in all groups indicate that the treatment intensity of the stereotactic body radiotherapy was insufficient to control colorectal cancer bone metastases.

Dose-Dependent Radiation-Induced Myocardial Damage in Esophageal Cancer Treated With Chemoradiotherapy: A Prospective Cardiac Magnetic Resonance Imaging Study

Purpose

The purpose of this prospective study was to evaluate radiation-induced myocardial damage after mediastinal radiation therapy (RT) using late gadolinium-enhancement (LGE) magnetic resonance imaging (MRI).

Methods and Materials

We enrolled 19 patients with esophageal cancer who were expected to have long-term survival by definitive treatment. They underwent delayed contrast-enhanced MRI (19 patients before treatment, 19 patients 6 months after treatment, and 12 patients 1.5 years after treatment). Dose distribution of the left ventricle was made using computed tomography, and the dose volume histogram of the left ventricle was calculated. Myocardial signal intensities in individual MRIs were normalized by the mean values in regions receiving low doses (<5 Gy). Changes in the normalized signal intensities after mediastinal radiation therapy were compared among regions where irradiation doses were 0 to 10 Gy, 10 to 20 Gy, 20 to 30 Gy, 30 to 40 Gy, 40 to 50 Gy, and 50 to 60 Gy, and we investigated whether intensity change was detected in a dose-dependent manner.

Results

The registered patients were treated with concurrent chemoradiotherapy with a median total dose of 60 Gy (50.4-66 Gy). Chemotherapy consisting of cisplatin and 5-fluorouracil was administered. In the population-based dose-response curve, dose-dependent intensity changes progressively increased in regions receiving more than 30 Gy. The averages of relative intensity change at 6 months and 1.5 years after treatment were 1.1% and −1.9% at 20 to 30 Gy and 37.5% and 17.5% at 40 to 50 Gy, respectively. LGE in regions receiving more than 30 Gy was detected in 68% (13/19) of the patients.

Conclusions

A dose-dependent relationship for myocardial signal intensity change was found by using LGE MRI. It may be necessary to reduce the volume of the myocardium receiving more than 30 Gy.

Phase 2 Clinical Trial of Stereotactic Body Radiation Therapy for Painful Nonspine Bone Metastases

PURPOSE

The present multicenter, single-arm, phase 2 study aimed to prospectively evaluate the palliative efficacy of stereotactic body radiation therapy (SBRT) in patients with painful nonspine bone metastases.

METHODS AND MATERIALS

Patients with painful (≥2 points on a 0-to-10 scale) nonspine bone metastases from a solid tumor were enrolled. The prescribed dose was 35 Gy in 5 fractions. The primary endpoint was overall pain response rate (complete response [CR] and partial response [PR]) as measured per the International Consensus on Palliative Radiotherapy Endpoints guideline 6 months after SBRT.

RESULTS

Forty-one osseous lesions in 38 patients were registered between June 2018 and June 2019. All lesions satisfied the inclusion criteria, and the patients completed the protocol treatment. Patients most commonly had lung cancer (22%), followed by prostate cancer, uterus cancer, and renal cell carcinoma (15%, 15%, and 12%, respectively). Bone metastases were most commonly located in coxal bones (56%). The median duration of follow-up after registration was 8 months (range, 1-19 months). Among evaluable lesions at 3 and 6 months after SBRT, the 3- and 6-month pain response rates were 78% and 75%, respectively. The local control rate at 6 months was 92%. Seven patients (17%) experienced bone fracture after irradiation, and 3 patients (7%) experienced grade 2 limb edema. One patient had regrowth of coxal bone metastases, and the tumor penetrated the sigmoid colon. Soft tissue abscess around the tumor and osteonecrosis of coxal bones were confirmed. The patient died of infection 4 months after SBRT and was determined to be a possible treatment-related death.

CONCLUSIONS

This prospective clinical trial showed that SBRT for nonspine bone metastases was effective in terms of pain palliation. These findings warrant a larger randomized controlled trial to compare SBRT with conventional radiation therapy. Additionally, operation history should be considered as a risk factor for edema.

Extreme skeletal muscle loss during induction chemotherapy is an independent predictor of poor survival in advanced epithelial ovarian cancer patients

AIM

Skeletal muscle loss is often observed in advanced cancer patients. This study investigates whether skeletal muscle loss is associated with survival outcomes of advanced epithelial ovarian cancer (EOC) patients after induction chemotherapy (IC) in a Japanese cohort. Whether serum inflammatory markers are associated with skeletal muscle changes is also addressed.

METHODS

We retrospectively reviewed 60 patients with stage III/IV EOC who underwent IC between 2010 and 2017. Skeletal muscle area (SMA) was measured at the third lumbar vertebrae level on a single axial computed tomography-scan image. Receiver operating curve analysis was used to determine cut-off values of pre- and post-IC SMA and SMA ratio (SMAR). Univariate and multivariate analyses of overall survival (OS) were conducted using the log-rank test and Cox proportional hazards regression model, respectively.

RESULTS

The SMA decreased significantly after IC (P = 0.019). The cut-off value between low and high SMAR was 0.96. High or low SMAR was observed in 34 (57%) and 26 (43%) patients, respectively. Univariate analysis revealed that low SMAR was associated with poor OS (P = 0.025). Multivariate analysis showed that incomplete resection during interval debulking surgery (hazard ratio, 0.30; 95% CI, 0.11-0.80; P = 0.016) and a low SMAR (hazard ratio, 3.17; 95% CI, 1.18-9.06; P = 0.022) were independent predictors of poor OS. Of the serum inflammatory markers investigated, only post-IC absolute neutrophil count correlated significantly with SMAR (P = 0.012).

CONCLUSION

Low SMAR can be used to predict poor prognosis in advanced EOC patients who have undergone IC.

Development of a dynamic deformable thorax phantom for the quality management of deformable image registration

The purpose of this study was to develop a novel dynamic deformable thorax phantom for deformable image registration (DIR) quality assurance (QA) and to verify as a tool for commissioning and DIR QA. The phantom consists of a base phantom, an inner phantom, and a motor-derived piston. The base phantom is an acrylic cylinder phantom with a diameter of 180 mm. The inner phantom consists of deformable, 20 mm thick disk-shaped sponges. To evaluate the physical characteristics of the phantom, we evaluated its image quality and deformation. DIR accuracies were evaluated using the three types of commercially DIR software (MIM, RayStation, and Velocity AI) to test the feasibility of this phantom. We used different DIR parameters to test the impact of parameters on DIR accuracy in various phantom settings. To evaluate DIR accuracy, a target registration error (TRE) was calculated using the anatomical landmark points. The three locations (i.e., distal, middle, and proximal positions) had different displacement amounts. This result indicated that the inner phantom was not moved but deformed. In cases with different phantom settings and marker settings, the ranges of the average TRE were 0.63-15.60 mm (MIM). In cases with different DIR parameters settings, the ranges of the average TRE were as follows: 0.73-7.10 mm (MIM), 8.25-8.66 mm (RayStation), and 8.26-8.43 mm (Velocity). These results suggest that our phantom could evaluate the detailed DIR behaviors with TRE. Therefore, this is indicative of the potential usefulness of our phantom in DIR commissioning and QA.

Evaluation of four-dimensional cone beam computed tomography ventilation images acquired with two different linear accelerators at various gantry speeds using a deformable lung phantom

We evaluated four-dimensional cone beam computed tomography (4D-CBCT) ventilation images (VI_CBCT) acquired with two different linear accelerator systems at various gantry speeds using a deformable lung phantom. The 4D-CT and 4D-CBCT scans were performed using a computed tomography (CT) scanner, an X-ray volume imaging system (Elekta XVI) mounted in Versa HD, and an On-Board Imager (OBI) system mounted in TrueBeam. Intensity-based deformable image registration (DIR) was performed between peak-exhale and peak-inhale images. VI_CBCT- and 4D-CT-based ventilation images (VI_CT) were derived by DIR using two metrics: one based on the Jacobian determinant and one on changes in the Hounsfield unit (HU). Three different DIR regularization values (λ) were used for VI_CBCT. Correlations between the VI_CBCT and VI_CT values were evaluated using voxel-wise Spearman's rank correlation coefficient (r). In case of both metrics, the Jacobian-based VI_CBCT with a gantry speed of 0.6 deg/sec in Versa HD showed the highest correlation for all the gantry speeds (e.g., λ = 0.05 and r = 0.68). Thus, the r value of the Jacobian-based VI_CBCT was greater or equal to that of the HU-based VI_CBCT. In addition, the ventilation accuracy of VI_CBCT increased at low gantry speeds. Thus, the image quality of VI_CBCT was affected by the change in gantry speed in both the imaging systems. Additionally, DIR regularization considerably influenced VI_CBCT in both the imaging systems. Our results have the potential to assist in designing CBCT protocols, incorporating VI_CBCT imaging into the functional avoidance planning process.

The impact of 4DCT-ventilation imaging-guided proton therapy on stereotactic body radiotherapy for lung cancer

Functional lung avoidance during radiotherapy can help reduce pulmonary toxicity. This study assessed the potential impact of four-dimensional computed tomography (4DCT)-ventilation imaging-guided proton radiotherapy (PT) on stereotactic body radiotherapy (SBRT) by comparing it with three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT), which employ photon beams. Thirteen lung cancer patients who received SBRT with 3D-CRT were included in the study. 4DCT ventilation was calculated using the patients' 4DCT data, deformable image registration, and a density-change-based algorithm. Three functional treatment plans sparing the functional lung regions were developed for each patient using 3D-CRT, VMAT, and PT. The prescribed doses and dose constraints were based on the Radiation Therapy Oncology Group 0618 protocol. We evaluated the region of interest (ROI) and functional map-based dose-function metrics for 4DCT ventilation and the irradiated dose. Using 3D-CRT, VMAT, and PT, the percentages of the functional lung regions that received ≥ 5 Gy (fV5) were 26.0%, 21.9%, and 10.7%, respectively; the fV10 were 14.4%, 11.4%, and 9.0%, respectively; and fV20 were 6.5%, 6.4%, and 6.6%, respectively, and the functional mean lung doses (fMLD) were 5.6 Gy, 5.2 Gy, and 3.8 Gy, respectively. These results indicated that PT resulted in a significant reduction in fMLD, fV5, and fV10, but not fV20. The use of PT reduced the radiation to highly functional lung regions compared with those for 3D-CRT and VMAT while meeting all dose constraints.

Radiation therapy and the risk of herpes zoster in patients with cancer

BACKGROUND

The role and impact of radiation therapy (RT) on the development of herpes zoster (HZ) has not been well studied. The objective of this study was to investigate the association between RT and HZ.

METHODS

A propensity score-matched, retrospective cohort study was conducted using institutional cancer registry data and medical records from 2011 to 2015. The risk of developing HZ in the RT and non-RT groups was compared using a Cox proportional hazards model. Associations also were explored between the RT field and the anatomic location of HZ in patients who developed HZ after RT. The expected number of HZ events within the radiation field was calculated according to the RT received by each patient; then, this number was compared with the observed number of in-field events.

RESULTS

Of 17,655 patients, propensity score matching yielded 4350 pairs; of these, 3891 pairs were eligible for comparison. The cumulative incidence of HZ in the RT group (vs the non-RT group) during the first 5 years after the index date was 2.1% (vs 0.7%) at 1 year, 3.0% (vs 1.0%) at 2 years, 3.4% (vs 1.3%) at 3 years, 4.1% vs 1.7% at 4 years, and 4.4% vs 1.8% at 5 years. The RT group showed a significantly higher risk of HZ than the non-RT group (hazard ratio, 2.59, 95% CI, 1.84-3.66). In the 120 patients who developed HZ after RT, HZ events were observed significantly more frequently within the RT field than expected (74 vs 43.8 events; P < .001).

CONCLUSIONS

Patients with cancer who received RT showed a significantly higher risk of HZ, which was commonly observed within the radiation field.

Quantitative analysis of intra-fractional variation in CT-based image guided brachytherapy for cervical cancer patients

We quantified intra-fractional dose variation and organ movement during CT-based 3D-image guided brachytherapy (3D-IGBT) in cervical cancer patients. Fifteen patients who underwent CT-based 3D-IGBT were studied. For all patients, pre-delivery CT for treatment planning after applicator insertion and post-delivery CT after dose delivery without changing the applicator position were acquired. Pre- and post-delivery CT were rigidly fused by matching the inserted applicator and planned dose on pre-delivery CT (pre-delivery dose) was mapped on post-delivery CT (post-delivery dose). D2, D1, and D0.1 cm³ of the rectum and bladder were compared between pre- and post-delivery doses with contours on each CT image. Organ movement and deformation was evaluated using deformation vector fields calculated by deformable image registration between pre- and post-delivery CT. We also evaluated dose variation and DVF between with and without a catheter to control filling. Differences in all DVH parameters were <±3% in physical dose and ± 5% in EQD2. However, a > 15% dose difference was found in 13.8% of the fractions in rectum D2 cm³ and in 11.1% of those in bladder D2 cm³. The mean value of DVF for bladder was larger than that of rectum, especially for the superior-inferior (S-I) direction. Insertion catheters in bladder reduced mean dose and DVF variation compared with that of without catheters. In fraction groups with large dose increasing, DVF in the S-I direction was significantly larger than that of other fraction groups. Our results indicated that preparation is needed to reduce changes in the S-I direction affect dose variation.

Search for Electron Antineutrino Appearance in a Long-Baseline Muon Antineutrino Beam

Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.

Variations Between Dose-Ventilation and Dose-Perfusion Metrics in Radiation Therapy Planning for Lung Cancer

Purpose

Currently, several active clinical trials of functional lung avoidance radiation therapy using different imaging modalities for ventilation or perfusion are underway. Patients with lung cancer often show ventilation-perfusion mismatch, whereas the significance of dose-function metric remains unclear. The aim of the present study was to compare dose-ventilation metrics with dose-perfusion metrics for radiation therapy plan evaluation.

Methods and Materials

Pretreatment 4-dimensional computed tomography and ^99mTc-macroaggregated albumin single-photon emission computed tomography perfusion images of 60 patients with lung cancer treated with radiation therapy were analyzed. Ventilation images were created using the deformable image registration of 4-dimensional computed tomography image sets and image analysis for regional volume changes as a surrogate for ventilation. Ventilation and perfusion images were converted into percentile distribution images. Analyses included Pearson’s correlation coefficient and comparison of agreements between the following dose-ventilation and dose-perfusion metrics: functional mean lung dose and functional percent lung function receiving 5, 10, 20, 30, and 40 Gy (fV₅, fV₁₀, fV₂₀, fV₃₀, and fV₄₀, respectively).

Results

Overall, the dose-ventilation metrics were greater than the dose-perfusion metrics (ie, fV₂₀, 26.3% ± 9.9% vs 23.9% ± 9.8%). Correlations between the dose-ventilation and dose-perfusion metrics were strong (range, r = 0.94-0.97), whereas the agreements widely varied among patients, with differences as large as 6.6 Gy for functional mean lung dose and 11.1% for fV₂₀. Paired t test indicated that the dose-ventilation and dose-perfusion metrics were significantly different.

Conclusions

Strong correlations were present between the dose-ventilation and dose-perfusion metrics. However, the agreement between the dose-ventilation and dose-perfusion metrics widely varied among patients, suggesting that ventilation-based radiation therapy plan evaluation may not be comparable to that based on perfusion. Future studies should elucidate the correlation of dose-function metrics with clinical pulmonary toxicity metrics.

Homology-based radiomic features for prediction of the prognosis of lung cancer based on CT-based radiomics

PURPOSE

Radiomics is a new technique that enables noninvasive prognostic prediction by extracting features from medical images. Homology is a concept used in many branches of algebra and topology that can quantify the contact degree. In the present study, we developed homology-based radiomic features to predict the prognosis of non-small-cell lung cancer (NSCLC) patients and then evaluated the accuracy of this prediction method.

METHODS

Four datasets were used: two to provide training and test data and two for the selection of robust radiomic features. All the datasets were downloaded from The Cancer Imaging Archive (TCIA). In two-dimensional cases, the Betti numbers consist of two values: b₀ (zero-dimensional Betti number), which is the number of isolated components, and b₁ (one-dimensional Betti number), which is the number of one-dimensional or "circular" holes. For homology-based evaluation, computed tomography (CT) images must be converted to binarized images in which each pixel has two possible values: 0 or 1. All CT slices of the gross tumor volume were used for calculating the homology histogram. First, by changing the threshold of the CT value (range: -150 to 300 HU) for all its slices, we developed homology-based histograms for b₀ , b₁ , and b₁ /b₀ using binarized images. All histograms were then summed, and the summed histogram was normalized by the number of slices. 144 homology-based radiomic features were defined from the histogram. To compare the standard radiomic features, 107 radiomic features were calculated using the standard radiomics technique. To clarify the prognostic power, the relationship between the values of the homology-based radiomic features and overall survival was evaluated using LASSO Cox regression model and the Kaplan-Meier method. The retained features with nonzero coefficients calculated by the LASSO Cox regression model were used for fitting the regression model. Moreover, these features were then integrated into a radiomics signature. An individualized rad score was calculated from a linear combination of the selected features, which were weighted by their respective coefficients.

RESULTS

When the patients in the training and test datasets were stratified into high-risk and low-risk groups according to the rad scores, the overall survival of the groups was significantly different. The C-index values for the homology-based features (rad score), standard features (rad score), and tumor size were 0.625, 0.603, and 0.607, respectively, for the training datasets and 0.689, 0.668, and 0.667 for the test datasets. This result showed that homology-based radiomic features had slightly higher prediction power than the standard radiomic features.

CONCLUSIONS

Prediction performance using homology-based radiomic features had a comparable or slightly higher prediction power than standard radiomic features. These findings suggest that homology-based radiomic features may have great potential for improving the prognostic prediction accuracy of CT-based radiomics. In this result, it is noteworthy that there are some limitations.

Postradiotherapy persistent lymphopenia as a poor prognostic factor in patients with cervical cancer receiving radiotherapy: a single-center, retrospective study

BACKGROUND

Radiotherapy (RT) is effective in cervical cancer; radiation-induced lymphopenia correlates with poor survival outcome in several cancer types. We investigated the association of total lymphocyte count (TLC) with survival outcomes in patients with cervical cancer.

METHODS

We retrospectively reviewed 168 patients with cervical cancer initially treated with definitive RT. We obtained clinicopathological data and TLCs before RT and at the end and at 6 months after RT. Patient-, treatment-, and tumor-specific factors were evaluated to determine their predictive values for overall survival. The association of overall and progression-free survivals with lymphopenia at each point was evaluated.

RESULTS

Median follow-up duration was 44 (interquartile range: 25-67) months. Median TLCs before RT and at the end and at 6 months after RT were 1625/mm³, 400/mm³, and 800/mm³ (interquartile range: 1270-1930/mm³, 290-550/mm³, and 600-1067/mm³), respectively. For overall survival, in addition to FIGO stage, body mass index, histology, treatment, and presence of para-aortic lymph node metastasis, lymphopenia at 6 months after RT was a poor prognostic factor in multivariate analysis (P = 0.0026; hazard ratio [HR], 3.06; 95% confidence interval [CI]: 1.48-6.33). For progression-free survival, TLCs before and at 6 months after RT were poor prognostic factors in univariate analysis (P = 0.0318 and 0.0081, respectively); however, the latter was the only independent prognostic factor in multivariate analysis (P = 0.0021; HR, 2.67; 95% CI: 1.43-4.99).

CONCLUSION

Post-RT persistent lymphopenia could be a poor prognostic factor for patients with cervical cancer who receive RT.

A low albumin to globulin ratio with a high serum globulin level is a prognostic marker for poor survival in cervical cancer patients treated with radiation based therapy

OBJECTIVE

We investigated whether the pretreatment albumin to globulin ratio, serum albumin level, and serum globulin level can be used to predict survival among cervical cancer patients treated with radiation based therapy and assessed globulin fractions.

METHODS

We retrospectively enrolled 128 patients with cervical cancer treated with radiation based therapy at our institution between 2010 and 2015. The associations of the pretreatment albumin to globulin ratio, and serum albumin and globulin levels with overall survival were assessed. Additionally, the associations of the globulin fractions with the serum globulin levels and overall survival were evaluated.

RESULTS

Median follow-up duration was 30 months (IQR 16-44 months). A low albumin to globulin ratio (< 1.53) was found to be an independent prognostic factor for overall survival (HR= 3.07; 95% CI, 1.03 to 13.3; P=0.044). On evaluating serum globulin and albumin separately, a high serum globulin level was significantly associated with overall survival (cut-off value 2.9 g/dL; HR=3.74; 95% CI 1.08 to 23.6; P=0.036) whereas a low serum albumin level was not associated with overall survival (cut-off value 3.6 g/dL; HR=1.77; 95% CI 0.57 to 4.54; P=0.29). Electrophoresis data of the serum proteins revealed that the γ-globulin fraction was most strongly correlated with the globulin levels (P<0.001). Furthermore, a high γ-globulin level (≥1.28 g/dL) was significantly associated with poor overall survival (log rank test, P=0.034).

CONCLUSIONS

A pretreatment low albumin to globulin ratio, which might be attributable to a high serum globulin level, can be used to predict poor prognosis in cervical cancer patients treated with radiation based therapy.