Irradiated Sites Research Articles

Pathological Assessment of Cardiac Radioablation to the Cavotricuspid Isthmus without Gating and Real-Time Tracking in Mini Pigs

<h3>Purpose/Objective(s)</h3> Cardiac arrhythmias are usually treated with invasive, time consuming catheter ablation techniques. While recently stereotactic body radiotherapy (SBRT) is an emerging non-invasive treatment in the management of cardiac arrhythmias. Although we used the motion management by compression techniques for the reduction of the internal target volume, we did not use the gating and real-time tracking techniques. We assessed the necessity of the precise target planning and monitoring the complex respiratory and cardiac motion to cardiac radioablation to the cavotricuspid isthmus (CTI) by pathological assessment in mini pigs. <h3>Materials/Methods</h3> All animal procedures were approved by institutional animal care and use committee and performed in full compliance with its guidelines. Four mini pigs underwent magnetic resonance (MR) and electrophysiology assessment using electroanatomic mapping (EAM) before and 3 months after SBRT with single-fraction doses of 25Gy. The target of CTI was defined by cardiologist. We defined the internal margin (IM), respiratory: SI 7 mm, AP 3 mm, LR 3 mm, cardiac motion: 3 mm in all direction and set up margin (SM): 5 mm in all direction. Then, planning target volume (PTV) margin: IM + SM = SI 15 mm, AP 10mm, LR 10 mm were added to the target, defining PTV.MR examination, including diffusion-weighted, dynamic Gd-enhanced, spectroscopy, and T2-weighted images were performed before and 3 months after SBRT, followed by histopathologic examination. Radiation oncologist and radiologist evaluated the detectability and image quality for the irradiated site. MRI findings of the CTI radioablation lesion was compared to electrophysiology and histopathology findings. <h3>Results</h3> A total dose of 25 Gy was successfully delivered to PTV in a single procedure in all mini pigs. EAM visualized the irradiated site and confirmed clockwise conduction block across the CTI. MRI could not detect the radiation injury clearly. Pathological examinations were analyzed after 3 months of follow-up, fibrous hyperplasia and capillary hyperplasia were observed around the nerve bundle beyond CTI in all pigs. The atrophy and necrosis of the nerve bundle itself is scarce. <h3>Conclusion</h3> These data demonstrated the feasibility of SBRT for creating conduction block across the CTI in mini pigs. Fibrosis or scarring around the nerve bundle beyond CTI may affect the radiation injury. Then, precise margins of cardiac radioablation to the cavotricuspid isthmus will reduce the radiation injury. Not only gating and breath-hold, but also including the use of real-time tracking such as MRI-guidance cardiac radiosurgery will open the possibility of treating cardiac arrhythmias patients completely safety and noninvasively.

The Toxicity of Low-Dose Whole Abdomen Radiotherapy in Advanced Gynecologic Malignancies Receiving Stereotactic Body Radiotherapy and Immunotherapy

<h3>Purpose/Objective(s)</h3> The objective of this retrospective study was to evaluate the safety of low-dose whole abdomen radiotherapy (LD-WART) in patients with gynecologic malignancies receiving stereotactic body radiotherapy (SBRT) and immunotherapy (IO). We hypothesized that LD-WART volume would not be associated with increased adverse events (AEs). <h3>Materials/Methods</h3> Study design was a pooled secondary analysis of two prospective phase I trials, in which patients with advanced solid malignancies were treated with multi-site SBRT (≤4 sites) with IO. The study cohort (N = 22) was limited to patients with a gynecologic primary (ovarian or uterine) that received SBRT to ≥1 abdomino-pelvic site. IO was administered either concurrently (N = 8) or sequentially (i.e., within 7 days of SBRT, N = 14). IO regimens included pembrolizumab (N = 14), nivolumab plus urelumab (N = 6), and nivolumab plus cabiralizumab (N = 2). Whole abdominal cavities (with inclusion of the pelvis) were contoured for all patients. The kidneys and a 1cm isocentric contraction of the liver were excluded. Based on recent literature supporting immune reprogramming of the tumor microenvironment with doses of 0.5 to 2 Gy, the V0.5Gy (%), V1Gy (%), and V2Gy (%) for the whole abdomen were recorded. Time to CTCAE v4.0 grade 2-4 AEs and overall survival (OS) were defined as the time from start of SBRT to either toxicity or death, respectively. Toxicity was analyzed using the cumulative incidence function with death as a competing risk. Correlation between dose metrics and toxicity were analyzed using the Fine-Gray subdistribution hazard model, including the primary site and number of irradiated abdomino-pelvic sites as covariates. <h3>Results</h3> 22 patients met criteria for inclusion (73% ovarian, 27% endometrial). Median OS was 13.3 months. The median whole abdomen V0.5Gy, V1Gy, and V2Gy was 42% (range, 12% - 97.5%), 32% (range, 8% - 86%), and 26% (range, 6% - 77%), respectively. At 12 months (with 12 of 22 patients evaluable), the cumulative incidence of grade 3+ AEs was 9%, 9%, and 0% when whole abdomen V0.5Gy, V1Gy, and V2Gy exceeded the cohort median, in contrast to 18%, 18%, and 27%, respectively, when less than the cohort median. As a continuous variable in the multivariable Fine-Gray model, grade 3+ AEs were not increased with increasing whole abdomen V0.5Gy (subdistribution hazard ratio [SHR] 0.96, <i>P</i> = 0.26), V1Gy (SHR 0.95, <i>P</i> = 0.11), and V2Gy (SHR 0.95, <i>P</i> = 0.14). Similarly, the grade 2+ AEs were not increased with increasing whole abdomen V0.5Gy (SHR 0.98, <i>P</i> = 0.12), V1Gy (SHR 0.97, <i>P</i> = 0.08), and V2Gy (SHR 0.98, <i>P</i> = 0.17). There were no grade 2+ hepatic or renal AEs. <h3>Conclusion</h3> In this pooled analysis of two phase I trials, increasing LD-WART volume receiving 0.5-2 Gy was not associated with increased toxicity in the setting of SBRT and immunotherapy. These data support the potential safety of a future pilot study being explored by our institution for advanced gynecologic malignancies combining low-dose whole abdominal irradiation, SBRT to gross tumor sites, and IO.

Synergistic Expression of the Abscopal Effect in a Murine Tumor Model Treated with Combined Radiation and Single or Dual-Immune Checkpoint Blockade

<h3>Purpose/Objective(s)</h3> Clinical studies have found that the abscopal effect is increased if radiotherapy (RT) is administered in combination with immunotherapy (IO). This study sought further evidence for a synergistic abscopal effect by combining RT with both single- and dual-immune checkpoint blockade in a murine tumor model. <h3>Materials/Methods</h3> Forty-two immunocompetent KRAS-LSL-G12D/+/p53KO mice were implanted with syngeneic KP-1 tumor cells in both the upper and lower back and randomized into 7 groups. Group 1 controls were administered sham treatment. Group 2 received RT with 8 Gy x 3 fractions delivered to the lower back tumors only. Group 3 was given 250 μg of murine anti-PD-1 monoclonal antibody as an intraperitoneal (IP) injection. Group 4 was treated identically but with 250 μg of murine anti-CTLA-4 monoclonal antibody. The remaining groups received both RT to the lower back tumors and an IP injection: 250 μg anti-PD-1 antibody (Group 5), 250 μg anti-CTLA-4 antibody (Group 6), or both anti-PD-1 antibody and anti-CTLA-4 antibody (Group 7). Tumor growth was measured with calipers at both the non-irradiated (upper back) site and the irradiated (lower back) site on days 1-15. <h3>Results</h3> RT administered to lower back tumors produced a smaller increase in mean tumor volume (197 mm³, p<0.0001) than sham treatment (511 mm³) or IO alone (anti-PD-1= 472 mm³, p=0.05; anti-CTLA-4= 563 mm³, p=0.25; Table 1). All combinations of RT and IO reduced lower back tumor growth more than sham treatment or IO alone (RT+anti-PDL-1 = 175 mm³, p<0.0001; RT+anti-CTLA-4 = 200 mm³ p<0.0001; RT+anti-PD-1+anti-CTLA-4 = 154 mm³, p<0.0001). No difference in the growth of lower back tumors was observed among groups receiving any combination of RT and IO. For the non-irradiated upper back tumors, tumor growth was reduced when RT to the lower back tumor was combined with either anti-PD-1 (p=0.0002) or anti-CTLA-4 (p=0.04). RT in combination with two IO agents produced better control of upper back tumor growth (209 mm³) than sham treatment (770 mm³, p<0.0001), RT alone (716 mm³, p<0.0001), anti-PD-1 alone (594 mm³, p<0.0001), anti-CTLA-4 alone (1050 mm³, p<0.0001), or RT in combination with a single IO agent (RT+anti-PD-1 = 411 mm³, p<0.0001; RT+anti-CTLA-4 = 600 mm³, p=0.004). Body weight did not change significantly throughout the trial for any group. <h3>Conclusion</h3> The synergistic abscopal effect in non-irradiated secondary murine tumors is optimized when RT to primary tumors is administered with dual-immune checkpoint blockade.

Irradiation Induced Activation of cGAS/STING Signaling Promotes Macrophage Anti-Tumor Activity via CXCL9, CXCL10-CXCR3 Axis

<h3>Purpose/Objective(s)</h3> Irradiation induced abundant dsDNA fragments, which can stimulate tumor immune responses by DNA sensing pathway. However, the underlying mechanism, mainly involved immune cells remains unknown. Herein we discovered that macrophage was the main immune cell involved in cGAS/STING DNA sensing pathway induced anti-tumor immune response, and macrophage derived CXCL9, CXCL10 played an important role in infiltration of T cells in tumor via CXCL9, CXCL10-CXCR3 axis. <h3>Materials/Methods</h3> cGAS knockout mice (cGAS-/- mice) and STING-deficient mice were used in the study. Xenograft tumor mouse model was established for in vivo study, using murine hepatoma cell line H22 or ovalbumin (OVA)-expressing H22. Irradiation locally delivered to the tumor area at 8 Gy/day for 3 days using a micro-CT/micro irradiator. <h3>Results</h3> Macrophage was found recruitment to the irradiated tumor site after irradiation. Using C57BL/6J mice bearing xenograft H22 tumors, we found cGAS-/- mice showed higher growth rate after irradiation comparing to tumors growing on wild type mice (WT mice). Using a both sides subcutaneous H22-OVA tumor mouse model, we found a substantial increased OVA-specific CD8+ T cells within the DLN(draining lymph node) of right irradiated tumor of WT mice, but low level within the right DLN of the irradiated tumor of STING-deficient mice and the no-irradiated right tumors of STING-deficient mice or WT mice, which confirmed that cGAS/STING pathway was involved in the radiation-mediated immunomodulation and promoted the radiation-induced adaptive anti-tumor immune activation. We also noted macrophage depletion partial reverse antitumor effect of irradiation in WT tumors, while no significant difference is observed in cGAS^−/− tumor, which revealed macrophage was the main immune cell involved in cGAS/STING DNA sensing pathway induced anti-tumor immune response. Further mechanism study revealed macrophage derived CXCL9, CXCL10 was induced by radiation in a cGAS/STING pathway dependent manner. Intraperitoneal injection of anti-CXCL9, CXCL10 significantly reduce the anti-tumor effect of irradiation in WT mice, but not in STING-deficient mice, these observations suggested macrophage derived CXCL9, CXCL10 were involved in infiltration of T cells in tumor via CXCL9, CXCL10-CXCR3 axis. <h3>Conclusion</h3> cGAS/STING pathway is crucial in the radiation-induced adaptive anti-tumor immune activation. macrophage derived CXCL9, CXCL10, which induced by radiation in a cGAS/STING pathway dependent manner, mediated infiltration of T cells in tumor via CXCL9, CXCL10- CXCR3 axis.

Bombarding Oligoprogression: Oncologic Outcomes Following Localized Radiotherapy in Oligoprogressive Non-Small Cell Lung Cancer Patients on Maintenance Systemic Therapy

<h3>Purpose/Objective(s)</h3> The purpose of this study is to evaluate the efficacy and toxicity of focal radiotherapy (RT) to all oligoprogressive sites to prolong the durability of current systemic therapy or meaningful clinical benefit (MCB) in patients with metastatic non-small cell lung cancer (NSCLC) and one to five sites of progressive disease. The primary endpoints include progression-free survival (PFS) and MCB. Secondary endpoints include overall survival (OS), local control (LC), event free survival (EFS), and toxicities of RT. <h3>Materials/Methods</h3> Treatment records at our institution were reviewed (2018 to 2021) and included if they had metastatic NSCLC, started maintenance systemic therapy, developed oligoprogression (1-5 sites), and all oligoprogressive sites amenable to and treated with RT with the intent for MCB. Prior RT was allowed. Kaplan-Meier survival analysis and log-rank testing were performed using R-Studio software. PD-L1 status and actionable mutations were also documented. Toxicities were documented using the CTCAE v5.0. <h3>Results</h3> From our records, 23 patients were identified and met inclusion criteria. Thirteen (57%) were female and 10 were male. Twenty-one (91%) of patients had adenocarcinoma, 10 (43%) had actionable mutations, and 13 (57%) had PD-L1 expression > 1%. 13 patients (56%) were on PD1/PD-L1 checkpoint inhibition, 7 (30%) patients were on EGFR-targeted therapy, and 3 (13%) patients were receiving chemotherapy alone. A total of 41 targets were irradiated with a median of 2 per patient (range 1 to 4), with 28 (68%) targets receiving stereotactic body radiotherapy or radiosurgery, 12 (29%) receiving intensity-modulated radiotherapy, and 1 (2%) receiving 3D conformal RT. At a median follow-up of 12.6 months, there were 17 progression events; 6 patients started next-line therapy and 6 were recommended no further therapy based on declining performance status or no suitable next line systemic therapy. Four patients received additional targeted radiotherapy for oligoprogression and did not switch therapies. Median PFS, OS, and EFS were 8.4 months (IQR 4.1 – 17.5), 17.2 months (IQR 12.6 – 31.4), and 8.3 months (IQR 2.7 – 12.0), respectively. At 12 months follow-up, 6 (43%) of 14 living patients maintained their systemic therapy without initiating next-line therapy. Median time to start of next line therapy (MCB) was not reached in this analysis due to few events. There was one local failure of an irradiated site yielding an in-field failure rate of 4%. Two patients (9%) had grade 3 chronic toxicity related to RT and were medically managed. <h3>Conclusion</h3> We identified that in oligoprogressive metastatic NSCLC patients, targeted RT to all progressive sites yielded high rates of LC and favorable rates of PFS and MCB. Future prospective trials with well-selected oligoprogressive patients are warranted to further evaluate the role of focal RT to oligoprogressive sites in this patient population.

Comprehensive Salvage Radiotherapy for Limited Relapsed B-Cell Non-Hodgkin Lymphoma Following CD19 Chimeric Antigen Receptor T-Cell Therapy

<h3>Purpose/Objective(s)</h3> Significant relapse rates following CD19 Chimeric Antigen Receptor T-Cell Therapy (CART) for relapsed/refractory (r/r) B-cell non-Hodgkin lymphoma (NHL) remain a challenge. This study aims to better define the role of salvage radiotherapy (SRT) after CART. <h3>Materials/Methods</h3> We retrospectively reviewed 48 patients with r/r aggressive B-cell NHL who received SRT following CART from 2018 to 2021. SRT local control rate (LC) - calculated based on the total number of irradiated sites, freedom from subsequent progression (FFSP), freedom from subsequent event (FFSE) – accounting for subsequent progressions and salvage therapies, and overall survival (OS) were defined from SRT start date. In-field recurrence was defined as disease relapse occurring within the radiation planning target volume. SRT was defined as comprehensive (compSRT) – treated all sites of active disease – or focal (focSRT). Limited disease was defined as disease amenable to comprehensive RT, either as localized (encompassable in one RT field) or oligo-diffuse (≤4 sites). Kaplan-Meier plots and Cox regression modeling were used to estimate the desired output. <h3>Results</h3> Median age of the cohort at time of CART infusion was 58 (range 19-73) years, and median time from CART infusion to SRT was 103 (range: 23-842) days. The median equivalent 2 Gy dose (EQD2) was 37.4 Gy (range 4-52 Gy) for compSRT and 24.2 Gy (range 4.7-48.8) for focSRT. The most common regimens were 36 Gy in 12 fractions in compSRT and 20 Gy in 5 fractions in focSRT. A total of 65 sites treated in 37 patients had adequate imaging follow-up after SRT. Of the irradiated sites, 21 lesions (32%) in 16 patients experienced in-field recurrence, translating to 1-year LC of 62%. No in-field recurrence occurred beyond 210 days. On univariate analysis, tumor size, SUVmax, and LDH >2x upper limit (UL) at the time of SRT were significantly associated with increased risk of in-field recurrence. On the multivariate analysis, LDH >2x UL (OR 6.5, CI: 1.8-24.3; p=0.005) and SUVmax (OR 1.06, CI: 1.002-1.12; p=0.044) retained significant association with in-field recurrence. There were 37 patients with limited disease and 11 with extensive disease and the 1-year OS was 39% and 0% (p<0.001), respectively. Among those with limited disease, 26 received compSRT and 11 received focSRT. At a median follow-up period of 20 months, patients with limited disease who received compSRT had significantly higher 1-year FFSP (31% vs. 0%; p<0.001), 1-year FFSE (19% vs. 0%; p=0.01), and 1-year OS (51% vs. 12%; p=0.028) compared to focSRT. <h3>Conclusion</h3> Post-CART compSRT for r/r B-cell NHL is a reasonable salvage intervention for patients with limited relapsed disease and is associated with better FFSP, FFSE and OS compared to focSRT. Patients who have elevated LDH >2 x UL and high SUVmax prior to SRT are likely at the highest risk of in-field recurrence and may benefit from escalation of therapy.

Liposome Formulation for Tumor-Targeted Drug Delivery Using Radiation Therapy.

Targeted delivery of drugs or other therapeutic agents through internal or external triggers has been used to control and accelerate the release from liposomal carriers in a number of studies, but relatively few utilize energy of therapeutic X-rays as a trigger. We have synthesized liposomes that are triggered by ionizing radiation (RTLs) to release their therapeutic payload. These liposomes are composed of natural egg phosphatidylethanolamine (PE), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, and 1,2-disteroyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)-2000] (DSPE-PEG-2000), and the mean size of the RTL was in the range of 114 to 133 nm, as measured by nanoparticle tracking analysis (NTA). The trigger mechanism is the organic halogen, chloral hydrate, which is known to generate free protons upon exposure to ionizing radiation. Once protons are liberated, a drop in internal pH of the liposome promotes destabilization of the lipid bilayer and escape of the liposomal contents. In proof of principle studies, we assessed RTL radiation-release of fluorescent tracers upon exposure to a low pH extracellular environment or exposure to X-ray irradiation. Biodistribution imaging before and after irradiation demonstrated a preferential uptake and release of the liposomes and their cargo at the site of local tumor irradiation. Finally, a potent metabolite of the commonly used chemotherapy irinotecan, SN-38, was loaded into RTL along with near infrared (NIR) fluorescent dyes for imaging studies and measuring tumor cell cytotoxicity alone or combined with radiation exposure, in vitro and in vivo. Fully loaded RTLs were found to increase tumor cell killing with radiation in vitro and enhance tumor growth delay in vivo after three IV injections combined with three, 5 Gy local tumor radiation exposures compared to either treatment modality alone.

European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation: definition, reporting, and clinical decision making.

Re-irradiation can be considered for local recurrence or new tumours adjacent to a previously irradiated site to achieve durable local control for patients with cancer who have otherwise few therapeutic options. With the use of new radiotherapy techniques, which allow for conformal treatment plans, image guidance, and short fractionation schemes, the use of re-irradiation for different sites is increasing in clinical settings. Yet, prospective evidence on re-irradiation is scarce and our understanding of the underlying radiobiology is poor. Our consensus on re-irradiation aims to assist in re-irradiation decision making, and to standardise the classification of different forms of re-irradiation and reporting. The consensus has been endorsed by the European Society for Radiotherapy and Oncology and the European Organisation for Research and Treatment of Cancer. The use of this classification in daily clinical practice and research will facilitate accurate understanding of the clinical implications of re-irradiation and allow for cross-study comparisons. Data gathered in a uniform manner could be used in the future to make recommendations for re-irradiation on the basis of clinical evidence. The consensus document is based on an adapted Delphi process and a systematic review of the literature was done according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Lingual laser frenotomy in newborns with ankyloglossia: a prospective cohort study

BackgroundThe study aims to describe the lingual laser frenotomy perioperative protocol for newborns with ankyloglossia with or without breastfeeding difficulties developed by Odontostomatology and Neonatology and Neonatal Intensive Care Units of the Aldo Moro University of Bari.MethodsAuthors carried out a prospective observational cohort study. Newborns with ankyloglossia (classified by using both Coryllos’ and Hazelbaker’s criteria) with or without difficult breastfeeding (according to Infant Breastfeeding Assessment Tool) underwent diode laser frenotomy (800 ± 10 nm; 5 W; continuous wave mode; contact technique; under topical anesthesia) and follow-up visits after seven and thirty days postoperatively. The authors analyzed as main outcomes the perioperative pain intensity measured by the C.R.I.E.S. scale, the occurrence of complications and quality of healing, the quality of breastfeeding, newborn’s postoperative weight gain, maternal nipple pain, and the presence of lesions as secondary outcomes.ResultsFifty-six newborns were included in the current study. Intraoperative mean pain intensity was 5.7 ± 0.5 points, resolved within thirty postoperative minutes. Observed complications were mild punctuating bleeding, carbonization of the irradiated site, and transitory restlessness. All wounds were completely healed within the thirtieth postoperative day. During follow-up, a significant breastfeeding improvement was evident with satisfactory newborns’ weight gain and a significant reduction of nipple pain and lesions (p < .05).ConclusionOur lingual laser frenotomy protocol provided significant breastfeeding improvement in the mother-newborn dyads with low intraoperative pain and no significant complications.

Patterns of relapse and long-term outcome in patients treated with a curative intent for advanced Hodgkin lymphoma

Background Consolidation radiotherapy for advanced Hodgkin lymphoma (AHL) is controversial. Precise knowledge of the most likely relapse location is crucial for radiotherapy planning. We performed detailed patterns of relapse analyses and evaluated if initial bulky disease, initial 18F-fluoro-deoxy-glucose (FDG)-avidity and/or a residual mass on computed tomography (CT)-scan after chemotherapy are sites with a high risk of relapse. This information could provide guidance for optimal use of radiotherapy in AHL. Material and methods We included 133 patients treated with curatively intended chemotherapy for AHL. 23 patients received consolidation radiotherapy. For relapsed patients, imaging from diagnosis, response evaluation, relapse, and any radiotherapy planning, were retrieved and co-registered to determine the exact site(s) of relapse relative to initial site(s), residual mass(es) and to any irradiated volumes. Size and FDG-avidity of initial sites with later relapse, and residual CT-abnormalities after chemotherapy in these sites were registered. Survival analyses were done using the Kaplan–Meier method. Results Nine (6.8%) patients relapsed, eight in initially involved sites. One relapse was in an initially irradiated site (as well as other sites). Initial bulky disease, high initial FDG-uptake, and/or residual masses on CT-scan after chemotherapy did not predict sites with a high risk of relapse. Overall survival was 79.6% (95% CI, 72.7–86.5%) and 70.6% (95% CI, 62.4–78.8%) at 5 and 10 years, respectively. Time to progression analysis showed 91.8% (95% CI, 86.9–96.7%) and 90.7% (95% CI, 85.4–96.0%) without progression at 5 and 10 years, respectively. Conclusion Current treatment strategies for AHL provide excellent disease control. Neither initial bulk, high initial FDG-uptake, nor a residual CT-abnormality post-chemotherapy seem to indicate sites with a high risk of relapse.

763 Radiation injury upregulates miR-196, increases dermal collagen, and triggers a pro-fibrotic genomic response that spreads in a murine model of radiation-induced skin fibrosis

Radiation-induced skin fibrosis (RISF) is a devastating result of cutaneous injury by irradiation that is delivered as part of clinical care, causing functional impairment and diminished quality of life for patients. To model RISF, we irradiated C57BL/6 mice (n=6) and collected skin from irradiated and non-irradiated sites after 24 weeks. Fibrosis was quantified by measuring dermal thickness and by machine learning ultrastructure analysis of dermal collagen network in tissue sections. Collagen levels were measured by hydroxyproline assay.

False-Positive Findings on Bone Scintigraphy after MRI-Guided Stereotactic Ablative Radiotherapy for Osseous Oligometastasis

Radical radiation therapy for oligorecurrent prostate cancer is considered to improve both overall and disease-specific survival. Therefore, accurate diagnosis by imaging is important when considering the indications for radiation therapy. We present a case of marginal recurrence of bone metastases from castrationresistant prostate cancer previously treated with radical radiation therapy, which could not be detected by bone single photon emission computed tomography/ computed tomography (SPECT/CT) but could be diagnosed by 68Ga-prostate-specific membrane antigen positron emission tomography/computed tomography (68Ga-PSMA PET/CT). Bone SPECT/CT showed false-positive tracer uptake in the lesion previously irradiated. 68Ga-PSMA PET/CT scan showed no abnormal uptake in the previously irradiated lesion, but showed intense uptake in the newly developed metastasis near the irradiated site. 68Ga-PSMA PET/CT scan may be able to diagnose marginal recurrence after radiation therapy more accurately than bone SPECT/CT

QS42. Closing The Gap on Clinical Translation of Cell-Based Therapies: A Novel Technique For Intraoperative Isolation of the Stromal Vascular Fraction for Bone Tissue Engineering

Purpose: Adipose-derived stems cells (ASC) have demonstrated promise across many areas of regenerative medicine, including bone tissue engineering. One major barrier to clinical translation and broad application of these therapeutics is current protocols which require laboratory cell culture and enzymatic digestion to produce stem cell rich product. More optimal methodologies would circumvent the current protocols, and instead, employ mechanically-based techniques to produce ASC rich stromal vascular fraction (SVF) intraoperatively for immediate clinical application. Therefore, the purpose of this study was to develop a clinically translatable technique for intra-operative harvest, isolation, and implantation of SVF with the primary aim of enhancing bone healing at irradiated fracture sites. Methods: Male Lewis rats (n=29) were divided into groups: Fracture (Fx), Radiation with Fracture (XRT), and Radiation with Fracture and SVF implantation (SVF). Experimental groups received 35Gy of radiation. All groups underwent mandibular osteotomy and external fixation. Inguinal fat pads were minced and serially processed using Tulip Sizing Transfers (2.4mm, 1.4mm, 1.2mm). Serial filtration (800 micron, 400 micron) and centrifugation was performed. The resultant oil and aqueous layers were discarded and the cell pellet was collected for immediate implantation at the osteotomy site. Animals were sacrificed on post-operative day 40. Gross pathology and MicroCT analysis were utilized to determine union rates and the quality of the bone formed at the osteotomy site. Biomechanical strength testing was performed until failure to evaluate yield and ultimate load of new bone at the osteotomy site. Results: Immediate implantation of SVF increased union rates compared to XRT alone (79% vs. 20%). Additionally, MicroCT analysis demonstrated high quality new bone formation in irradiated fractures treated with SVF compared to the control based on bone mineral density (666.2 ± 32.0 vs. 312.2 ± 51.7; p=0.000) and bone volume fraction (0.744 ± 0.072 vs. 0.350 ± 0.041; p=0.000). In fact, implantation of SVF into irradiated fracture sites resulted in bone quality similar to the bone formed at non-irradiated fracture sites, as there was no significant difference found between groups (BMD: 666.2 ± 32.0 vs. 710.3 ± 38.0; p=0.390, BVF: 0.744 ± 0.072 vs. 0.803 ± 0.04; p=0.300). Radiation significantly diminished the biomechanical properties of bone, including yield (23.6 ± 28.2 vs. 81.9 ± 31.3; p=0.002) and ultimate load (33.7 ± 30.9 vs. 87.3 ± 26.7; p=0.005). SVF implantation improved yield (52.0 ± 28.6 vs. 81.9 ± 31.3; p=0.161) and ultimate load (33.7 ± 30.9 vs. 87.3 ± 26.7; p=0.145) of the irradiated bone to the level of the non-irradiated control, as there was no significant difference between groups. Conclusions: Use of the stromal vascular fraction for bone tissue engineering demonstrates great potential, including applications in irradiated fracture healing. In this study, we developed a novel approach that eliminates laboratory dependent techniques and instead, utilizes mechanical methods that would enable intraoperative SVF harvest, isolation, and immediate implantation. While further studies are required to optimize this approach, the results of this study are incredibly promising for the long-awaited translation of cell-based therapeutics into the clinical arena.

Abstract 5516: Nanoparticle-enhanced radiotherapy combined with triple blockade of PD1, LAG3, and TIGIT enhances anti-tumor immune activation

Abstract Introduction: Checkpoint inhibition (CPI) has been a game-changer for cancer therapy, but most cancers do not respond. Part of the problem is that cancers employ multiple checkpoints; thus, targeting multiple checkpoint receptors simultaneously may yield increased benefit. Previously, we found that radiotherapy (XRT) in concert with a radiation-enhancing nanoparticle (NBTXR3) and PD1 blockade significantly improved tumor control both at the irradiative site and in remote, unirradiated tumors in a mouse model of anti-PD1 (αPD1)-resistant lung cancer (344SQR). Here, we tested whether blockade of TIGIT, LAG3, and PD1 in combination with NBTXR3-enhanced XRT could improve antitumor immune responses in our 344SQR tumor model. Methods: Fifty thousand 344SQR cells were inoculated in the right and left hindlimbs of 129Sv/Ev mice on day 0 and day 4 to establish primary and secondary tumors, respectively. Mice were divided into six treatment groups: 1) untreated; 2) XRT+αPD1; 3) NBTXR3+XRT+αPD1; 4) NBTXR3+XRT+αPD1+αLAG3; 5) NBTXR3+XRT+αPD1+αTIGIT; and 6) NBTXR3+XRT+αPD1+αLAG3 +αTIGIT. Primary tumors were intratumorally injected with NBTXR3 nanoparticles on day 7 and received 3 fractions of 12 Gy X-ray radiation on days 8, 9, and 10. Immune checkpoint inhibitors, composed of αPD1 (200 μg), αLAG3 (200 μg), and αTIGIT (200 μg), were intraperitoneally administered to the mice on days 5, 8, 11, 14. The expression of 770 immune-related genes were measured via NanoString from the RNA extracted from the primary and secondary tumors on day 21. Results: CPIs+NBTXR3-enhanced radiation significantly promoted the upregulation of mRNA transcripts involved in innate immunity, the humoral response, B cell function, dendritic cell (DC) function, and antigen processing within primary, irradiated tumors relative to untreated controls. No additional increase in immune gene activity in the irradiated tumors was observed when LAG3, TIGIT, or both were blocked in addition to PD1. However, within the non-irradiated tumors, triple blockade of PD1, LAG3, and TIGIT in concert with NBTXR3+XRT produced elevations in multiple immune-related pathways that were significantly higher than those produced by other treatment combinations. These pathways included both adaptive and innate immunity; B, T, and natural killer (NK) cell, and DC function; and antigen processing. Conclusions: Simultaneous inhibition of LAG3 and TIGIT in tandem with PD1 blockade and NBTXR3-enhanced radiotherapy promotes immune activation at the irradiated site. In addition, abscopal immune responses are improved with blockade of LAG3 and TIGIT. These results suggest that blockade of multiple immune checkpoints in parallel with NBTXR3-mediated radiotherapy may be effective in metastatic cancers. [Y.H. and B.G. contributed equally to this work.] Citation Format: Yun Hu, Genevieve Bertolet, Sebastien Paris, Hampartsoum Barsoumian, Jordan DA SILVA, Saumil Gandhi, Quynh-Nhu Nguyen, Maria A. Cortez, James W. Welsh. Nanoparticle-enhanced radiotherapy combined with triple blockade of PD1, LAG3, and TIGIT enhances anti-tumor immune activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5516.

In-field recurrences in relapsed/refractory (R/R) B-cell non-Hodgkin lymphoma (NHL) bridged with radiation prior to CD19 chimeric antigen receptor T-cell therapy (CART).

7556 Background: The majority of R/R NHL progressions after CART involve pre-existing sites, suggesting a promising role for bridging radiotherapy (bRT). We assessed the local control rate of disease sites bridged with radiotherapy prior to CART and identified predictors of in-field recurrence. Methods: We retrospectively reviewed 35 patients with aggressive B-cell NHL who received bRT between leukapheresis and CART infusion between 2018 and 2021 at a multi-site single institution. bRT local control rate (LC), calculated based on the total number of irradiated sites, was defined from bRT end date. Progression-free survival (PFS) and overall-survival (OS) were defined from the date of CART infusion. In-field recurrence was defined as disease relapse occurring within the radiation planning target volume. Kaplan-Meier plots and cox regression modeling were used to estimate the desired output. Results: Median age of the cohort at time of CART infusion was 59 (range 19-73). The median equivalent 2 Gy dose (EQD2) administered was 23.3 Gy (range 4-41 Gy). The median time from end of bRT to CART infusion was 14 days (range 6-42). Five (14%) patients also received bridging chemotherapy with bRT. Among the 34 evaluable patients, 30 (88%) achieved an objective response (59% complete response and 29% partial response). At a median follow-up of 12 months, 1-year PFS was 48% and 1-year OS was 72%. No progression occurred beyond 240 days. On review of treatment plans and pre-treatment PET/CT scans, 59 sites were identified that received bRT prior to CART infusion. The median size and SUVmax of the irradiated sites were 8.7cm (range 1.5-22) and 13 (range 4-46), respectively. Of the 59 irradiated sites, 8 sites (13.6%) in 7 patients had in-field local recurrence, translating to 1-year LC of 84%. No in-field recurrence occurred beyond 180 days. Moreover, no local recurrence occurred in patients who received radiation to all known sites of active disease to EQD2&gt; 30 Gy (n = 4 patients); these patients remained in remission except for 1 who experienced progression outside the bRT field. On univariate analysis, triple hit lymphoma (THL) (OR 22.8, 95% CI: 3.8-138.3; p &lt; 0.001), tumor size (OR 1.25, 95% CI: 1.1-1.4; p &lt; 0.001), specifically ≥ 9cm (OR 9.4, CI: 1.2-77.3; p = 0.036) and SUVmax (OR 1.1, CI: 1.02-1.15; p = 0.008), specifically ≥ 20 (OR 5.6, CI: 1.3-23.7; p = 0.018), were significantly associated with increased risk of in-field recurrence. On multivariate analysis, THL (OR 32.9, CI: 3.2-336.0; p = 0.03) and tumor size (OR 1.3, CI: 1.1-1.6; p = 0.01) retained significant association with in-field recurrence. Conclusions: Bridging radiotherapy prior to CART provides excellent and durable in-field local control for R/R B-cell NHL. Patients with triple hit histology and bulky disease are likely at higher risk of in-field recurrence and may benefit from higher doses of bRT.

An Autobioluminescent Method for Evaluating In Vitro and In Vivo Growth of Rhodococcus equi.

ABSTRACTA previously reported method for evaluating the intracellular growth of Rhodococcus equi using enhanced green fluorescent protein is unsuitable for the quantitative evaluation of the entire sample because the signal can be detected only in the excitation region. Therefore, we created an autobioluminescent R. equi using luciferase (luxABCDE). First, we connected luxABCDE to the functional promoter PaphII and introduced it into the chromosomes of ATCC33701 and ATCC33701_P-. Luminescence was detected in both transformants, and a correlation between the bacterial number and luminescence intensity in the logarithmic phase was observed, indicating that luxABCDE is functionally and quantitatively expressed in R. equi. The luminescence of ATCC33701 was significantly higher than that of ATCC33701_P- at 24 h after infection with J774A.1. Next, RNA-Seq analysis of ATCC33701 to search for endogenous high-expression promoters resulted in the upstream sequences of RS29370, RS41760, and vapA being selected as candidates. Luminescence was detected in each transformant expressing the luxABCDE using these upstream sequences. We examined the luminescence intensity by coexpressing the frp gene, an enhancer of the luciferase reaction, with luxABCDE. The luminescence intensity of the coexpressing transformant was significantly enhanced in J774A.1 compared with the non-coexpressing transformant. Finally, we examined the luminescence in vivo. The luminescence signals in the organs peaked on the third day following the administration of ATCC33701 derivatives in mice, but no luminescence signal was detected when the ATCC33701_P- derivative was administered. The autologous bioluminescent method described herein will enhance the in vitro and in vivo quantitative analysis of R. equi proliferation.IMPORTANCE We established an autologous bioluminescent strain of R. equi and a method to evaluate its proliferation in vitro and in vivo quantitatively. This method overcomes the weakness of the fluorescence detection system that only measures the site of excitation light irradiation. It is expected to be used as an in vitro and in vivo growth evaluation method with excellent quantitative properties. In addition, it was suggested that the selection of a promoter that expresses luxABCDE could produce a luminescence with high intensity. Although this method needs further improvement, such as creating transformants that can maintain high luminescence intensity regardless of environmental changes such as temperature fluctuations, it is possible to observe bacterial growth over time in mice without killing them. Therefore, this method can be used to not only evaluate the pathogenicity of various wild and gene-deficient strains but also to screen preventive and therapeutic methods such as vaccines.

T-Cell Repertoire in Tumor Radiation: The Emerging Frontier as a Radiotherapy Biomarker.

Simple SummaryRadiotherapy constitutes an essential component of the treatment for malignant disease. Besides its direct effect on cancer cells, namely, DNA damage and cell death, ionizing irradiation also mediates indirect antitumor effects that are mostly mediated by the immune system. Investigations into the processes underlying the interaction between radiotherapy and the immune system have uncovered mechanisms that can be exploited to promote the antitumor efficacy of radiotherapy both locally in the irradiated primary tumor and also at distant lesions in non-irradiated tumors. Because of its capacity to stimulate antitumor immunity, radiotherapy is also applied in combination with immune-checkpoint-inhibition-based immunotherapy. This review discusses the important pathways that govern the synergistic interactions between ionizing radiation and antitumor immune reactivity. Unravelling these involved mechanisms is mandatory for the successful application of anticancer radiotherapy and immunotherapy. We also place emphasis on the need for biomarkers that will aid in the selection of patients most likely to benefit from such combined treatments.Radiotherapy (RT) is a therapeutic modality that aims to eliminate malignant cells through the induction of DNA damage in the irradiated tumor site. In addition to its cytotoxic properties, RT also induces mechanisms that result in the promotion of antitumor immunity both locally within the irradiation field but also at distant tumor lesions, a phenomenon that is known as the “abscopal” effect. Because the immune system is capable of sensing the effects of RT, several treatment protocols have been assessing the synergistic role of radiotherapy combined with immunotherapy, collectively referred to as radioimmunotherapy. Herein, we discuss mechanistic insights underlying RT-based immunomodulation, which also enhance our understanding of how RT regulates antitumor T-cell-mediated immunity. Such knowledge is essential for the discovery of predictive biomarkers and for the improvement of clinical trials investigating the efficacy of radio-immunotherapeutic modalities in cancer patients.

Strontium-89 chloride delivery for painful bone metastases in patients with a history of prior irradiation.

Re-irradiation of a previously irradiated site must be done with careful consideration to minimize dose to organs at risk. To evaluate pain response and safety of Sr-89 administration for painful bone metastases after prior irradiation. We retrospectively reviewed patients with Sr-89 injection for painful bone metastasis in a previously irradiated site. All patients were seen in follow-up at 1, 2, 3, and 4months after injection and every 6months thereafter. Pain control, toxicity, and pain progression-free survival were analyzed. Correlation of pain relapse with the following characteristics was analyzed: gender, age, primary tumor, tumor pathology, baseline performance status, and baseline verbal rating scale. Among 25 patients analyzed (10 male, 15 female), median age was 68 (range, 50-81) years. Primary tumor sites included lung (n = 11), breast (n = 3), uterine cervix (n = 3), prostate (n = 3), and others (n = 5). Median follow-up was 25 (range, 1-76) months. Pain relief was observed in 24 patients (96.0%). One- and 2-year pain progression-free survival rates in these patients were 54.5% and 48.4%, respectively. Median time to pain progression was 5 (range, 2-16) months. Statistically significantly lower pain progression-free survival was observed in patients with osteolytic bone metastases (p < 0.01). No grade 3 or worse adverse events were observed. Sr-89 injection showed pain relief in most of our patients with painful bone metastases in a previously irradiated site and caused no grade 3 or worse adverse events. Sr-89 is an option for patients with a painful bone metastasis in a previously irradiated site.

Hyperbaric oxygen therapy treatment as an alternative for a chronic sinus tract after chordoma surgery and radiation.

Chordoma is a rare form of cancer that forms from the notochord remnants, and affects the skull and the spine. The standard treatment for a sacrococcygeal chordoma is surgery and radiation. Chordoma has a high rate of recurrence and surgery with radiation treatment can leave patients with surgical site complications, such as wounds, fistulas or sinus tracts. Repeat surgical intervention on an irradiated surgical site increases incidence of complications leading to decreased quality of life, and increased morbidity and mortality. Treatment of wound complications after surgery and high-dose radiation for a chordoma tumour is rarely reported in the literature. Herein, the author describes the case of a chronic sinus tract after surgery and radiation for a sacral chordoma tumour successfully healed by hyperbaric oxygen therapy (HBOT) in conjunction with topical antibiotics.

Free Flap Outcome in Irradiated Recipient Sites: A Systematic Review and Meta-analysis.

Background:The impact of previous radiotherapy on free flap outcome is still a subject of debate. Clinical investigations have come to divergent conclusions and the true effect of radiotherapy (XRT) on flap survival is not definitely known. Most studies investigating the factor often have their methodological limitations such as lack of statistical power as a consequence of the overall low failure rates together with few irradiated cases. This study will attempt to address the question whether previous radiotherapy is associated with a significantly higher incidence of flap failure or not.Methods:A systematic review and meta-analysis were conducted in concordance with the PRISMA protocol using the PubMed database. Fixed-effect and random-effect models were applied to obtain the odds ratio of total flap failure and partial flap failure between radiation and nonradiation groups. Statistical heterogeneity and publication bias were assessed and forest plots and funnel plots were constructed for graphic illustration.Results:A total of 43 studies were included for qualitative and quantitative analysis involving 18,776 flaps in 17,532 patients. Patients with preoperative XRT were significantly associated with an increased risk for total (odds ratio fixed = 1.675, 95% confidence interval [CI] = 1.405–1.996, P < 0.001) and partial free flap failure (odds ratio fixed = 2.161, 95% CI = 1.472–2.172, P < 0.001).Conclusion:The study suggests that preoperative radiotherapy is associated with an increased risk for total and partial free flap failure. Further studies are needed to investigate the effect of total XRT dose and time after radiation on free flap outcome.