Distinct p53 transcriptional programs dictate acute DNA-damage responses and tumor suppression.

The molecular basis for p53-mediated tumor suppression remains unclear. Here, to elucidate mechanisms of p53 tumor suppression, we use knockin mice expressing an allelic series of p53 transcriptional activation mutants. Microarray analysis reveals that one mutant, p53(25,26), is severely compromised for transactivation of most p53 target genes, and, moreover, p53(25,26) cannot induce G(1)-arrest or apoptosis in response to acute DNA damage. Surprisingly, p53(25,26) retains robust activity in senescence and tumor suppression, indicating that efficient transactivation of the majority of known p53 targets is dispensable for these pathways. In contrast, the transactivation-dead p53(25,26,53,54) mutant cannot induce senescence or inhibit tumorigenesis, like p53 nullizygosity. Thus, p53 transactivation is essential for tumor suppression but, intriguingly, in association with a small set of novel p53 target genes. Together, our studies distinguish the p53 transcriptional programs involved in acute DNA-damage responses and tumor suppression-a critical goal for designing therapeutics that block p53-dependent side effects of chemotherapy without compromising p53 tumor suppression.

Technical Note: A novel dosimeter improves total skin electron therapy surface dosimetry workflow.

PURPOSE: The novel scintillator-based system described in this study is capable of accurately and remotely measuring surface dose during Total Skin Electron Therapy (TSET); this dosimeter does not require post-exposure processing or annealing and has been shown to be re-usable, resistant to radiation damage, have minimal impact on surface dose, and reduce chances of operator error compared to existing technologies e.g. optically stimulated luminescence detector (OSLD). The purpose of this study was to quantitatively analyze the workflow required to measure surface dose using this new scintillator dosimeter and compare it to that of standard OSLDs. METHODS: Disc-shaped scintillators were attached to a flat-faced phantom and a patient undergoing TSET. Light emission from these plastic discs was captured using a time-gated, intensified, camera during irradiation and converted to dose using an external calibration factor. Time required to complete each step (daily QA, dosimeter preparation, attachment, removal, registration, and readout) of the scintillator and OSLD surface dosimetry workflows was tracked. RESULTS: In phantoms, scintillators and OSLDs surface doses agreed within 3% for all data points. During patient imaging it was found that surface dose measured by OSLD and scintillator agreed within 5% and 3% for 35/35 and 32/35 dosimetry sites, respectively. The end-to-end time required to measure surface dose during phantom experiments for a single dosimeter was 78 and 202 sec for scintillator and OSL dosimeters, respectively. During patient treatment, surface dose was assessed at 7 different body locations by scintillator and OSL dosimeters in 386 and 754 sec, respectively. CONCLUSION: Scintillators have been shown to report dose nearly twice as fast as OSLDs with substantially less manual work and reduced chances of human error. Scintillator dose measurements are automatically saved to an electronic patient file and images contain a permanent record of the dose delivered during treatment.

Tumor-stage mycosis fungoides in palmoplantar localization with large-cell transformation and partial CD30 expression shows complete response to brentuximab vedotin.

Mycosis fungoides in palmoplantar localization (MFPP) is a rare variant of MF that is confined to the hands and feet. Patients commonly receive treatment over many years for suspected palmoplantar dermatitis before the diagnosis is made. Most MFPP patients remain at patch or plaque stage, and often respond to treatment with radiotherapy. Herein, we describe a 77-year-old man who suffered 6 years of hand and foot dermatitis that failed multiple treatments, most notably TNF-α inhibitors and mycophenolate mofetil. He eventually developed a tumor on the hand, which was biopsied to reveal a dense dermal infiltrate of large lymphocytes (CD3+/CD4-/CD8-/TCR-BetaF1+/partial CD30+). A subsequent biopsy of an eczematous patch from his hand revealed an epidermotropic and syringotropic infiltrate comprised of smaller lymphocytes with a concordant immunophenotype and matching clonal peak with TCR gene rearrangement. He was diagnosed with MFPP and started on radiotherapy with a modest response; therefore, a decision was made to start brentuximab vedotin, which resulted in a complete response. MFPP is an exceedingly rare variant of MF that can show large-cell transformation and progress in stage. We highlight a possible association between disease progression and immunosuppressants and the potential role for treatment with brentuximab.

Light sheet luminescence imaging with Cherenkov excitation in thick scattering media.

Light scattering leads to a severe loss of axial and transverse resolution with depth into tissue, limiting accuracy and value of biomedical luminescence imaging techniques. High-resolution imaging beyond a few-millimeter depth is prohibited because diffusive transport dominates beyond a few scattering distances. In this study, light sheet imaging through scattering media is demonstrated using a radiotherapy linear accelerator to deliver well-defined thin scanned sheets of x-rays. These sheets produce Cherenkov light within the medium, which in turn excites luminescence of an optical probe across the sheet plane. This luminescence can then be imaged by an intensified camera positioned perpendicular to the sheet plane. The precise knowledge of the light sheet position within the medium allowed for efficient attenuation correction of the signal with depth as well as spatial deconvolution of the excitation light. Together these methods allowed for the first time, to the best of our knowledge, high-resolution imaging of tissue-equivalent phantoms up to 3 cm thick, yielding the precise position and shape of luminescent lesions located deep in tissue without the need for nonlinear image reconstruction.

Direct and Repeated Clinical Measurements of pO2 for Enhancing Cancer Therapy and Other Applications.

The first systematic multi-center study of the clinical use of EPR oximetry has begun, with funding as a PPG from the NCI. Using particulate oxygen sensitive EPR, materials in three complementary forms (India Ink, "OxyChips", and implantable resonators) the clinical value of the technique will be evaluated. The aims include using repeated measurement of tumor pO2 to monitor the effects of treatments on tumor pO2, to use the measurements to select suitable subjects for the type of treatment including the use of hyperoxic techniques, and to provide data that will enable existing clinical techniques which provide data relevant to tumor pO2 but which cannot directly measure it to be enhanced by determining circumstances where they can give dependable information about tumor pO2.

Cherenkov-excited luminescence scanned imaging.

Ionizing radiation is commonly delivered by medical linear accelerators (LINAC) in the form of shaped beams, and it is able to induce Cherenkov emission in tissue. In fluorescence-based microscopy excitation from scanned spots, lines, or sheets can be used for fast high-resolution imaging. Here we introduce Cherenkov-excited luminescence scanned imaging (CELSI) as a new imaging methodology utilizing 2-dimensional (∼5-mm-thick) sheets of LINAC radiation to produce Cherenkov photons, which in turn excite luminescence of probes distributed in biological tissues. Imaging experiments were performed by scanning these excitation sheets in three orthogonal directions while recording Cherenkov-excited luminescence. Tissue phantom studies have shown that single luminescent inclusions ∼1 mm in diameter can be imaged within 20-mm-thick tissue-like media with minimal loss of spatial resolution. Using a phosphorescent probe for oxygen, PtG4 with the CELSI methodology, an image of partial pressure of oxygen (pO2) was imaged in a rat lymph node, quantitatively restoring pO2 values in differently oxygenated tissues.

Advances in probes and methods for clinical EPR oximetry.

EPR oximetry, which enables reliable, accurate, and repeated measurements of the partial pressure of oxygen in tissues, provides a unique opportunity to investigate the role of oxygen in the pathogenesis and treatment of several diseases including cancer, stroke, and heart failure. Building on significant advances in the in vivo application of EPR oximetry for small animal models of disease, we are developing suitable probes and instrumentation required for use in human subjects. Our laboratory has established the feasibility of clinical EPR oximetry in cancer patients using India ink, the only material presently approved for clinical use. We now are developing the next generation of probes, which are both superior in terms of oxygen sensitivity and biocompatibility including an excellent safety profile for use in humans. Further advances include the development of implantable oxygen sensors linked to an external coupling loop for measurements of deep-tissue oxygenations at any depth, overcoming the current limitation of 10 mm. This paper presents an overview of recent developments in our ability to make meaningful measurements of oxygen partial pressures in human subjects under clinical settings.

Skeletal muscle and glioma oxygenation by carbogen inhalation in rats: a longitudinal study by EPR oximetry using single-probe implantable oxygen sensors.

The feasibility of EPR oximetry using a single-probe implantable oxygen sensor (ImOS) was tested for repeated measurement of pO2 in skeletal muscle and ectopic 9L tumors in rats. The ImOS (50 mm length) were constructed using nickel-chromium alloy wires, with lithium phthalocyanine (LiPc, oximetry probe) crystals loaded in the sensor loop and coated with AF 2400(®) Teflon. These ImOS were implanted into the skeletal muscle in the thigh and subcutaneous 9L tumors. Dynamic changes in tissue pO2 were assessed by EPR oximetry at baseline, during tumor growth, and repeated hyperoxygenation with carbogen breathing. The mean skeletal muscle pO2 of normal rats was stable and significantly increased during carbogen inhalation in experiments repeated for 12 weeks. The 9L tumors were hypoxic with a tissue pO2 of 12.8 ± 6.4 mmHg on day 1; however, the response to carbogen inhalation varied among the animals. A significant increase in the glioma pO2 was observed during carbogen inhalation on day 9 and day 14 only. In summary, EPR oximetry with ImOS allowed direct and longitudinal oxygen measurements in deep muscle tissue and tumors. The heterogeneity of 9L tumors in response to carbogen highlights the need to repeatedly monitor pO2 to confirm tumor oxygenation so that such changes can be taken into account in planning therapies and interpreting results.

Technical note: Visual, rapid, scintillation point dosimetry for in vivo MV photon beam radiotherapy treatments.

BACKGROUND: While careful planning and pre-treatment checks are performed to ensure patient safety during external beam radiation therapy (EBRT), inevitable daily variations mean that in vivo dosimetry (IVD) is the only way to attain the true delivered dose. Several countries outside the US require daily IVD for quality assurance. However, elsewhere, the manual labor and time considerations of traditional in vivo dosimeters may be preventing frequent use of IVD in the clinic. PURPOSE: This study expands upon previous research using plastic scintillator discs for optical dosimetry for electron therapy treatments. We present the characterization of scintillator discs for in vivo x-ray dosimetry and describe additional considerations due to geometric complexities. METHODS: Plastic scintillator discs were coated with reflective white paint on all sides but the front surface. An anti-reflective, matte coating was applied to the transparent face to minimize specular reflection. A time-gated iCMOS camera imaged the discs under various irradiation conditions. In post-processing, background-subtracted images of the scintillators were fit with Gaussian-convolved ellipses to extract several parameters, including integral output, and observation angle. RESULTS: Dose linearity and x-ray energy independence were observed, consistent with ideal characteristics for a dosimeter. Dose measurements exhibited less than 5% variation for incident beam angles between 0° and 75° at the anterior surface and 0-60 ∘ $^\circ $ at the posterior surface for exit beam dosimetry. Varying the angle between the disc surface and the camera lens did not impact the integral output for the same dose up to 55°. Past this point, up to 75°, there is a sharp falloff in response; however, a correction can be used based on the detected width of the disc. The reproducibility of the integral output for a single disc is 2%, and combined with variations from the gantry angle, we report the accuracy of the proposed scintillator disc dosimeters as ±5.4%. CONCLUSIONS: Plastic scintillator discs have characteristics that are well-suited for in vivo optical dosimetry for x-ray radiotherapy treatments. Unlike typical point dosimeters, there is no inherent readout time delay, and an optical recording of the measurement is saved after treatment for future reference. While several factors influence the integral output for the same dose, they have been quantified here and may be corrected in post-processing.

Neoadjuvant Therapies Do Not Reduce Epidermal Growth Factor Receptor (EGFR) Expression or EGFR-Targeted Fluorescence in a Murine Model of Soft-Tissue Sarcomas.

PURPOSE: ABY-029, an epidermal growth factor receptor (EGFR)-targeted, synthetic Affibody peptide labeled with a near-infrared fluorophore, is under investigation for fluorescence-guided surgery of sarcomas. To date, studies using ABY-029 have occurred in tumors naïve to chemotherapy (CTx) and radiation therapy (RTx), although these neoadjuvant therapies are frequently used for sarcoma treatment in humans. The goal of this study was to evaluate the impact of CTx and RTx on tumor EGFR expression and ABY-029 fluorescence of human soft-tissue sarcoma xenografts in a murine model. PROCEDURES: Immunodeficient mice (n = 98) were divided into five sarcoma xenograft groups and three treatment groups - CTx only, RTx only, and CTx followed by RTx, plus controls. Four hours post-injection of ABY-029, animals were sacrificed followed by immediate fluorescence imaging of ex vivo adipose, muscle, nerve, and tumor tissues. Histological hematoxylin and eosin staining confirmed tumor type, and immunohistochemistry staining determined EGFR, cluster of differentiation 31 (CD31), and smooth muscle actin (SMA) expression levels. Correlation analysis (Pearson's correlation coefficients, r) and linear regression (unstandardized coefficient estimates, B) were used to determine statistical relationships in molecular expression and tissue fluorescence between xenografts and treatment groups. RESULTS: Neoadjuvant therapies had no broad impact on EGFR expression (|B|≤ 7.0, p ≥ 0.4) or on mean tissue fluorescence (any tissue type, (|B|≤ 2329.0, p ≥ 0.1). Mean tumor fluorescence was significantly related to EGFR expression (r = 0.26, p = 0.01), as expected. CONCLUSION: Results suggest that ABY-029 as an EGFR-targeted, fluorescent probe is not negatively impacted by neoadjuvant soft-tissue sarcoma therapies, although validation in humans is required.

Anesthetic Oxygen Use and Sex Are Critical Factors in the FLASH Sparing Effect.

Purpose: Ultra High Dose-Rate (UHDR) radiation has been reported to spare normal tissue, compared with Conventional Dose-Rate (CDR) radiation. However, important work remains to be done to improve the reproducibility of the FLASH effect. A better understanding of the biologic factors that modulate the FLASH effect may shed light on the mechanism of FLASH sparing. Here, we evaluated whether sex and/or the use of 100% oxygen as a carrier gas during irradiation contribute to the variability of the FLASH effect. Methods and Materials: C57BL/6 mice (24 male, 24 female) were anesthetized using isoflurane mixed with either room air or 100% oxygen. Subsequently, the mice received 27 Gy of either 9 MeV electron UHDR or CDR to a 1.6 cm2 diameter area of the right leg skin using the Mobetron linear accelerator. The primary postradiation endpoint was time to full thickness skin ulceration. In a separate cohort of mice (4 male, 4 female), skin oxygenation was measured using PdG4 Oxyphor under identical anesthesia conditions. Results: Neither supplemental oxygen nor sex affected time to ulceration in CDR irradiated mice. In the UHDR group, skin damage occured earlier in male and female mice that received 100% oxygen compared room air and female mice ulcerated sooner than male mice. However, there was no significant difference in time to ulceration between male and female UHDR mice that received room air. Oxygen measurements showed that tissue oxygenation was significantly higher when using 100% oxygen as the anesthesia carrier gas than when using room air, and female mice showed higher levels of tissue oxygenation than male mice under 100% oxygen. Conclusions: The skin FLASH sparing effect is significantly reduced when using oxygen during anesthesia rather than room air. FLASH sparing was also reduced in female mice compared to male mice. Both tissue oxygenation and sex are likely sources of variability in UHDR studies. These results suggest an oxygen-based mechanism for FLASH, as well as a key role for sex in the FLASH skin sparing effect.

One Year of Clinic-Wide Cherenkov Imaging for Discovery of Quality Improvement Opportunities in Radiation Therapy.

PURPOSE: Cherenkov imaging is clinically available as a radiation therapy treatment verification tool. The aim of this work was to discover the benefits of always-on Cherenkov imaging as a novel incident detection and quality improvement system through review of all imaging at our center. METHODS AND MATERIALS: Multicamera Cherenkov imaging systems were permanently installed in 3 treatment bunkers, imaging continuously over a year. Images were acquired as part of normal treatment procedures and reviewed for potential treatment delivery anomalies. RESULTS: In total, 622 unique patients were evaluated for this study. We identified 9 patients with treatment anomalies occurring over their course of treatment, which were only detected with Cherenkov imaging. Categorizing each event indicated issues arising in simulation, planning, pretreatment review, and treatment delivery, and none of the incidents were detected before this review by conventional measures. The incidents identified in this study included dose to unintended areas in planning, dose to unintended areas due to positioning at treatment, and nonideal bolus placement during setup. CONCLUSIONS: Cherenkov imaging was shown to provide a unique method of detecting radiation therapy incidents that would have otherwise gone undetected. Although none of the events detected in this study reached the threshold of reporting, they identified opportunities for practice improvement and demonstrated added value of Cherenkov imaging in quality assurance programs.

Comparison of Tumor Control and Skin Damage in a Mouse Model after Ultra-High Dose Rate Irradiation and Conventional Irradiation.

Recent studies suggest ultra-high dose rate radiation treatment (UHDR-RT) reduces normal tissue damage compared to conventional radiation treatment (CONV-RT) at the same dose. In this study, we compared first, the kinetics and degree of skin damage in wild-type C57BL/6 mice, and second, tumor treatment efficacy in GL261 and B16F10 dermal tumor models, at the same UHDR-RT and CONV-RT doses. Flank skin of wild-type mice received UHDR-RT or CONV-RT at 25 Gy and 30 Gy. Normal skin damage was tracked by clinical observation to determine the time to moist desquamation, an endpoint which was verified by histopathology. Tumors were inoculated on the right flank of the mice, then received UHDR-RT or CONV-RT at 1 × 11 Gy, 1 × 15, 1 × 25, 3 × 6 and 3 × 8 Gy, and time to tumor tripling volume was determined. Tumors also received 1 × 11, 1 × 15, 3 × 6 and 3 × 8 Gy doses for assessment of CD8+/CD4+ tumor infiltrate and genetic expression 96 h postirradiation. All irradiations of the mouse tumor or flank skin were performed with megavoltage electron beams (10 MeV, 270 Gy/s for UHDR-RT and 9 MeV, 0.12 Gy/s for CONV-RT) delivered via a clinical linear accelerator. Tumor control was statistically equal for similar doses of UHDR-RT and CONV-RT in B16F10 and GL261 murine tumors. There were variable qualitative differences in genetic expression of immune and cell damage-associated pathways between UHDR and CONV irradiated B16F10 tumors. Compared to CONV-RT, UHDR-RT resulted in an increased latent period to skin desquamation after a single 25 Gy dose (7 days longer). Time to moist skin desquamation did not significantly differ between UHDR-RT and CONV-RT after a 30 Gy dose. The histomorphological characteristics of skin damage were similar for UHDR-RT and CONV-RT. These studies demonstrated similar tumor control responses for equivalent single and fractionated radiation doses, with variable difference in expression of tumor progression and immune related gene pathways. There was a modest UHDR-RT skin sparing effect after a 1 × 25 Gy dose but not after a 1 × 30 Gy dose.

Anesthetic oxygen use and sex are critical factors in the FLASH sparing effect.

Introduction: Ultra-high dose-rate (UHDR) radiation has been reported to spare normal tissue compared to conventional dose-rate (CDR) radiation. However, reproducibility of the FLASH effect remains challenging due to varying dose ranges, radiation beam structure, and in-vivo endpoints. A better understanding of these inconsistencies may shed light on the mechanism of FLASH sparing. Here, we evaluate whether sex and/or use of 100% oxygen as carrier gas during irradiation contribute to the variability of the FLASH effect. Methods: C57BL/6 mice (24 male, 24 female) were anesthetized using isoflurane mixed with either room air or 100% oxygen. Subsequently, the mice received 27 Gy of either 9 MeV electron UHDR or CDR to a 1.6 cm2 diameter area of the right leg skin using the Mobetron linear accelerator. The primary post-radiation endpoint was time to full thickness skin ulceration. In a separate cohort of mice (4 male, 4 female) skin oxygenation was measured using PdG4 Oxyphor under identical anesthesia conditions. Results: In the UHDR group, time to ulceration was significantly shorter in mice that received 100% oxygen compared to room air, and amongst them female mice ulcerated sooner compared to males. However, no significant difference was observed between male and female UHDR mice that received room air. Oxygen measurements showed significantly higher tissue oxygenation using 100% oxygen as the anesthesia carrier gas compared to room air, and female mice showed higher levels of tissue oxygenation compared to males under 100% oxygen. Conclusion: The FLASH sparing effect is significantly reduced using oxygen during anesthesia compared to room air. The FLASH sparing was significantly lower in female mice compared to males. Both tissue oxygenation and sex are likely sources of variability in UHDR studies. These results suggest an oxygen-based mechanism for FLASH, as well as a key role for sex in the FLASH skin sparing effect.

Remote dose imaging from Cherenkov light using spatially resolved CT calibration in breast radiotherapy.

PURPOSE: Imaging Cherenkov light during radiotherapy allows the visualization and recording of frame-by-frame relative maps of the dose being delivered to the tissue at each control point used throughout treatment, providing one of the most complete real-time means of treatment quality assurance. In non-turbid media, the intensity of Cherenkov light is linear with surface dose deposited, however the emission from patient tissue is well-known to be reduced by absorbing tissue components such as hemoglobin, fat, water, and melanin, and diffused by the scattering components of tissue. Earlier studies have shown that bulk correction could be achieved by using the patient planning computed tomography (CT) scan for attenuation correction. METHODS: In this study, CT maps were used for correction of spatial variations in emissivity. Testing was completed on Cherenkov images from radiotherapy treatments of post-lumpectomy breast cancer patients (n = 13), combined with spatial renderings of the patient radiodensity (CT number) from their planning CT scan. RESULTS: The correction technique was shown to provide a pixel-by-pixel correction that suppressed many of the inter- and intra-patient differences in the Cherenkov light emitted per unit dose. This correction was established from a calibration curve that correlated Cherenkov light intensity to surface-rendered CT number ( R 6 MV 2 = 0.70 $R_{6{\rm{MV}}}^2 = 0.70$ and R 10 MV 2 = 0.72 $R_{10{\rm{MV}}}^2 = 0.72$ ). The corrected Cherenkov intensity per unit dose standard error was reduced by nearly half (from ∼30% to ∼17%). CONCLUSIONS: This approach provides evidence that the planning CT scan can mitigate some of the tissue-specific attenuation in Cherenkov images, allowing them to be translated into near surface dose images.

Performance comparison of quantitative metrics for analysis of in vivo Cherenkov imaging incident detection during radiotherapy.

OBJECTIVES: Examine the responses of multiple image similarity metrics to detect patient positioning errors in radiotherapy observed through Cherenkov imaging, which may be used to optimize automated incident detection. METHODS: An anthropomorphic phantom mimicking patient vasculature, a biological marker seen in Cherenkov images, was simulated for a breast radiotherapy treatment. The phantom was systematically shifted in each translational direction, and Cherenkov images were captured during treatment delivery at each step. The responses of mutual information (MI) and the γ passing rate (%GP) were compared to that of existing field-shape matching image metrics, the Dice coefficient, and mean distance to conformity (MDC). Patient images containing other incidents were analyzed to verify the best detection algorithm for different incident types. RESULTS: Positional shifts in all directions were registered by both MI and %GP, degrading monotonically as the shifts increased. Shifts in intensity, which may result from erythema or bolus-tissue air gaps, were detected most by %GP. However, neither metric detected beam-shape misalignment, such as that caused by dose to unintended areas, as well as currently employed metrics (Dice and MDC). CONCLUSIONS: This study indicates that different radiotherapy incidents may be detected by comparing both inter- and intrafractional Cherenkov images with a corresponding image similarity metric, varying with the type of incident. Future work will involve determining appropriate thresholds per metric for automatic flagging. ADVANCES IN KNOWLEDGE: Classifying different algorithms for the detection of various radiotherapy incidents allows for the development of an automatic flagging system, eliminating the burden of manual review of Cherenkov images.

Treatment Planning System for Electron FLASH Radiation Therapy: Open-Source for Clinical Implementation.

PURPOSE: To present a Monte Carlo (MC) beam model and its implementation in a clinical treatment planning system (TPS, Varian Eclipse) for a modified ultrahigh dose-rate electron FLASH radiation therapy (eFLASH-RT) linear accelerator (LINAC) using clinical accessories and geometry. METHODS AND MATERIALS: The gantry head without scattering foils or targets, representative of the LINAC modifications, was modeled in the Geant4-based GAMOS MC toolkit. The energy spectrum (σE) and beam source emittance cone angle (θcone) were varied to match the calculated open-field central-axis percent depth dose (PDD) and lateral profiles with Gafchromic film measurements. The beam model and its Eclipse configuration were validated with measured profiles of the open field and nominal fields for clinical applicators. An MC forward dose calculation was conducted for a mouse whole-brain treatment, and an eFLASH-RT plan was compared with a conventional (Conv-) RT electron plan in Eclipse for a human patient with metastatic renal cell carcinoma. RESULTS: The eFLASH beam model agreed best with measurements at σE = 0.5 MeV and θcone = 3.9° ± 0.2°. The model and its Eclipse configuration were validated to clinically acceptable accuracy (the absolute average error was within 1.5% for in-water lateral, 3% for in-air lateral, and 2% for PDDs). The forward calculation showed adequate dose delivery to the entire mouse brain while sparing the organ at risk (lung). The human patient case demonstrated the planning capability with routine accessories to achieve an acceptable plan (90% of the tumor volume receiving 95% and 90% of the prescribed dose for eFLASH and Conv-RT, respectively). CONCLUSIONS: To our knowledge, this is the first functional beam model commissioned in a clinical TPS for eFLASH-RT enabling planning and evaluation with minimal deviation from the Conv-RT workflow. It facilitates the clinical translation because eFLASH-RT and Conv-RT plan quality were comparable for a human patient involving complex geometries and tissue heterogeneity. The methods can be expanded to model other eFLASH irradiators with different beam characteristics.

Epidermal growth factor-targeted fluorescence is unaffected by standard neoadjuvant therapies in human sarcomas.

Curative surgery for other many cancers requires that the tumor be removed with a zone of normal tissue surrounding the tumor with 'negative' margins. Sarcomas, cancers of the bones, muscles, and fat, require WLE for cure. Unfortunately, 'positive' margins occur in 20-25% of sarcoma surgeries, associated with cancer recurrence and reduced survival. Our group successfully tested a small-molecule fluorophore (ABY-029) in sarcomas that targets the epidermal growth factor receptor. We sought to evaluate human sarcoma xenografts for epidermal growth factor receptor expression and binding of ABY-029 with and without exposure to standard presurgical chemotherapy and radiation. We inoculated groups of 24 NSG mice with five cell lines (120 mice total). Eight mice from each cell line received: 1) radiation alone; 2) chemotherapy alone; or 3) chemotherapy and radiation. We administered ABY-029 2-4 hours before surgery. Tumor and biopsy portions of background tissues were removed. All tissues were imaged on a LI-COR Odyssey and processed in pathology. There were no significant reductions in epidermal growth factor receptor expression or in ABY-029-mediated fluorescence in tumors exposed to chemotherapy, radiation, or both. fluorescence-guided surgery demonstrates strong promise to improve curative surgical cancer care, particularly for sarcomas where the positive margin rate is substantial. Fluorophore performance must be evaluated under circumstances that duplicate accurately the biological milieu relevant to a particular cancer. This work shows that human sarcoma xenografts subjected to standard therapies do not demonstrate a change in epidermal growth factor receptor expression or in epidermal growth factor receptor-targeted fluorescence, thereby indicating that epidermal growth factor receptor-targeted fluorescence-guided surgery should be feasible under normal therapeutic conditions in the clinic.

Sensitizing brain metastases to stereotactic radiosurgery using hyperbaric oxygen: A proof-of-principle study.

PURPOSE: Increased oxygen levels may enhance the radiosensitivity of brain metastases treated with stereotactic radiosurgery (SRS). This project administered hyperbaric oxygen (HBO) prior to SRS to assess feasibility, safety, and response. METHODS: 38 patients were studied, 19 with 25 brain metastases treated with HBO prior to SRS, and 19 historical controls with 27 metastases, matched for histology, GPA, resection status, and lesion size. Outcomes included time from HBO to SRS, quality-of-life (QOL) measures, local control, distant (brain) metastases, radionecrosis, and overall survival. RESULTS: The average time from HBO chamber to SRS beam-on was 8.3 ± 1.7 minutes. Solicited adverse events (AEs) were comparable between HBO and control patients; no grade III or IV serious AEs were observed. Radionecrosis-free survival (RNFS), radionecrosis-free survival before whole-brain radiation therapy (WBRT) (RNBWFS), local recurrence-free survival before WBRT (LRBWFS), distant recurrence-free survival before WBRT (DRBWFS), and overall survival (OS) were not significantly different for HBO patients and controls on Kaplan-Meier analysis, though at 1-year estimated survival rates trended in favor of SRS + HBO: RNFS - 83% vs 60%; RNBWFS - 78% vs 60%; LRBWFS - 95% vs 78%; DRBWFS - 61% vs 57%; and OS - 73% vs 56%. Multivariate Cox models indicated no significant association between HBO treatment and hazards of RN, local or distant recurrence, or mortality; however, these did show statistically significant associations (p < 0.05) for: local recurrence with higher volume, radionecrosis with tumor resection, overall survival with resection, and overall survival with higher GPA. CONCLUSION: Addition of HBO to SRS for brain metastases is feasible without evident decrement in radiation necrosis and other clinical outcomes.

Clinical implementation of the first Cherenkov imaging system in a community-based hospital.

Purpose: To document experiences with one year of clinical implementation of the first Cherenkov imaging system and share the methods that we developed to utilize Cherenkov imaging to improve treatment delivery accuracy in real-time. Methods: A Cherenkov imaging system was installed commissioned and calibrated for clinical use. The optimal room lighting conditions and imaging setup protocols were developed to optimize both image quality and patient experience. The Cherenkov images were analyzed for treatment setup and beam delivery verification. Results: We have successfully implemented a clinical Cherenkov imaging system in a community-based hospital. Several radiation therapy patient setup anomalies were found in 1) exit dose to the contralateral breast, 2) dose to the chin due to head rotation for a supraclavicular field, 3) intrafractional patient motion during beam delivery, and 4) large variability (0.5 cm to 5 cm) in arm position between fractions. The system was used to deliver deep inspiration breath hold (DIBH) treatment delivery of an electron treatment beam. Clinical process and procedures were improved to mitigate the identified issues to ensure treatment delivery safety and to improve treatment accuracy. Conclusion: The Cherenkov imaging system has proven to be a valuable clinical tool for the improvement of treatment delivery safety and accuracy at our hospital. With only minimal training the therapists were able to adjust or correct treatment positions during treatment delivery as needed. With future Cherenkov software developments Cherenkov imaging systems could provide daily surface guided radiotherapy (SGRT) and real time treatment delivery quality control for all 3D and clinical setup patients without adding additional radiation image dose as in standard kV, MV and CBCT image verifications. Cherenkov imaging can greatly improve clinical efficiency and accuracy, making real time dose delivery consistency verification and SGRT a reality.