Efficacy of radiotherapy for gastric bleeding associated with advanced gastric cancer

Background Gastric bleeding negatively impacts the quality of life of patients with unresectable advanced gastric cancer and is frequently lethal. We investigated the efficacy of RT for palliation of gastric bleeding from gastric cancer and identified an optimal radiotherapy (RT) strategy. Methods The study analyzed 57 patients submitted to palliative RT for gastric bleeding associated with gastric cancer between January 2009 and February 2019. Changes in hemoglobin (Hb) levels were analyzed based on measurements taken before and immediately, 1 month, and 2 months after RT. Re-bleeding after RT was identified as either Hb level dropping to < 7.0 g/dL or the administration of a blood transfusion after RT. Results The median biologically effective dose (α/β = 10) was 37.5 Gy (range 23.6–58.5). The most common regimen was 25 Gy in five fractions. The mean Hb levels before, immediately after, 1 month, and 2 months after RT (6.6, 9.7, 10.3, and 9.7 g/dL, respectively) were significantly higher than that before RT (all p < 0.001). No significant differences in re-bleeding rates were observed according to total dose, fractional dose, and fraction number. Gastric tumor response evaluated by computed tomography within 2 months after RT showed partial responses were more frequent in patients achieving bleeding control (25.0% vs. 10.8%, p = 0.023) and overall survival was significantly improved for bleeding control within 3 months after RT (median, 15.4 vs. 10.0 weeks, p = 0.048). Conclusions RT was an effective modality for gastric bleeding control in gastric cancer, which can be achieved with a short course scheme with five fractions.

A Practical Approach for Continuous In Situ Characterization of Radiation Quality Factors in Space

The space radiation environment is qualitatively different from Earth, and its radiation hazard is generally quantified relative to photons using quality factors that allow assessment of biologically-effective dose. Two approaches exist for estimating radiation quality factors in complex radiation environments: One is a fluence-based risk cross-section approach, which requires very detailed in silico characterization of the radiation field and biological cross sections, and thus cannot realistically be used for in situ monitoring. By contrast, the microdosimetric approach, using measured (or calculated) distributions of microdosimetric energy deposition together with empirical biological weighting functions, is conceptually and practically simpler. To demonstrate feasibility of the microdosimetric approach, we estimated a biological weighting function for one specific endpoint, heavy-ion-induced tumorigenesis in APC1638N/+ mice, which was unfolded from experimental results after a variety of heavy ion exposures together with corresponding calculated heavy-ion microdosimetric energy deposition spectra. Separate biological weighting functions were unfolded for targeted and non-targeted effects, and these differed substantially. We folded these biological weighting functions with microdosimetric energy deposition spectra for different space radiation environments, and conclude that the microdosimetric approach is indeed practical and, in conjunction with in-situ measurements of microdosimetric spectra, can allow continuous readout of biologically-effective dose during space flight.

Biologically-Effective-Dose of Metribuzin, Applied Preemergence and Postemergence, for the Control of Waterhemp (Amaranthus tuberculatus) with Different Mechanisms of Resistance to Photosystem II-inhibiting herbicides

Photosystem II (PS II)-inhibitor herbicide resistance in Ontario waterhemp [Amaranthus tuberculatus (Moq.) Sauer] population is conferred via target-site resistance (TSR) and non-target-site resistance (NTSR) mechanisms. Metribuzin-resistant (MR) A. tuberculatus is due to TSR,. Conversely, in other populations of PS II-resistant A. tuberculatus, plants are resistant to atrazine but metribuzin-sensitive (MS). The objective of this study was to determine the biologically-effective-dose of metribuzin applied PRE and POST for the control of MS and MR A. tuberculatus. Ten field experiments were conducted in 2019 and 2020 to determine the effective doses of metribuzin for 50, 80, and 95% control of MS and MR A. tuberculatus. Metribuzin applied PRE at the calculated doses of 133, 350, and 1070 g ai ha-1 controlled MS A. tuberculatus 50, 80, and 95%, respectively, whereas the calculated doses of 7868 and 17533 g ai ha-1 controlled MR A. tuberculatus 50 and 80%, respectively at 12 WAA. Metribuzin applied POST at the calculated doses of 245 and 1480 g ai ha-1 controlled MS A. tuberculatus 50 and 80%, respectively; the calculated dose for 50% MR A. tuberculatus control was greater than the highest dose (17920 g ai ha-1) included in this study. Metribuzin at 560 and 1120 g ha-1 and pyroxasulfone/flumioxazin (240 g ai ha-1) applied PRE controlled MS A. tuberculatus 88, 95, and 98%, respectively at 12 WAA. The aforementioned treatments controlled MR A. tuberculatus 0, 4, and 93%, respectively at 12 WAA. Metribuzin at 560 and 1120 g ha-1 and fomesafen (240 g ai ha-1) applied POST controlled MS A. tuberculatus 65, 70, and 78%, and MR A. tuberculatus 0, 1, and 49%, respectively at 12 WAA. Based on these results, NTSR PS II-resistant A. tuberculatus (enhanced metabolism) is controlled with metribuzin applied PRE and POST, in contrast TSR PS II-resistant A. tuberculatus (glycine264serine altered target site) is not controlled with metribuzin.

Radiation Pneumonitis in Thoracic Cancer Patients: Multi-Center Voxel-Based Analysis

This study investigates the dose–response patterns associated with radiation pneumonitis (RP) in patients treated for thoracic malignancies with different radiation modalities. To this end, voxel-based analysis (VBA) empowered by a novel strategy for the characterization of spatial properties of dose maps was applied. Data from 382 lung cancer and mediastinal lymphoma patients from three institutions treated with different radiation therapy (RT) techniques were analyzed. Each planning CT and biologically effective dose map (α/β = 3 Gy) was spatially normalized on a common anatomical reference. The VBA of local dose differences between patients with and without RP was performed and the clusters of voxels with dose differences that significantly correlated with RP at a p-level of 0.05 were generated accordingly. The robustness of VBA inference was evaluated by a novel characterization for spatial properties of dose maps based on probabilistic independent component analysis (PICA) and connectograms. This lays robust foundations to the obtained findings that the lower parts of the lungs and the heart play a prominent role in the development of RP. Connectograms showed that the dataset can support a radiobiological differentiation between the main heart and lung substructures.

Biologically-effective-dose of pyraflufen-ethyl/2,4-D, applied preplant alone or mixed with metribuzin on glyphosate-resistant horseweed in soybean

Glyphosate resistance in weed species has presented immense challenges for farmers in Ontario. The co-application of burndown plus residual herbicides provides control of glyphosate-resistant (GR) horseweed control in soybean. Pyraflufen-ethyl/2,4-D is a premixed herbicide formulation sold under the tradename Blackhawk®. Five field experiments were conducted over a two-year period (2019, 2020) in fields in southwestern Ontario to ascertain the biologically-effective-dose of pyraflufen-ethyl/2,4-D, applied alone, or mixed with metribuzin, for GR horseweed control when applied pre-plant to soybean. Soybean visible injury for all treatments was <15%. At 8 wk after application (WAA), the calculated doses of pyraflufen-ethyl/2,4-D for 50, 80, and 95% GR horseweed control were 390, 1148, and >2108 g ha−1, respectively. The addition of metribuzin to pyraflufen-ethyl/2,4-D reduced the doses of pyraflufen-ethyl/2,4-D for 50, 80, and 95% GR horseweed control to 19, 46 and 201 g ha−1, respectively. Pyraflufen-ethyl/2,4-D + metribuzin controlled GR horseweed 97% which is comparable to the current industry standards. Based on these results, pyraflufen-ethyl/2,4-D + metribuzin (527 + 400 g ha−1) applied preplant can be used for GR horseweed control in soybean.