Differential Distribution of the DNA-PKcs Inhibitor Peposertib Selectively Radiosensitizes Patient-derived Melanoma Brain Metastasis Xenografts.

Radioresistance of melanoma brain metastases limits the clinical utility of conventionally fractionated brain radiation in this disease, and strategies to improve radiation response could have significant clinical impact. The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is critical for repair of radiation-induced DNA damage, and inhibitors of this kinase can have potent effects on radiation sensitivity. In this study, the radiosensitizing effects of the DNA-PKcs inhibitor peposertib were evaluated in patient-derived xenografts of melanoma brain metastases (M12, M15, M27). In clonogenic survival assays, peposertib augmented radiation-induced killing of M12 cells at concentrations ≥100 nmol/L, and a minimum of 16 hours exposure allowed maximal sensitization. This information was integrated with pharmacokinetic modeling to define an optimal dosing regimen for peposertib of 125 mpk dosed just prior to and 7 hours after irradiation. Using this drug dosing regimen in combination with 2.5 Gy × 5 fractions of radiation, significant prolongation in median survival was observed in M12-eGFP (104%; P = 0.0015) and M15 (50%; P = 0.03), while more limited effects were seen in M27 (16%, P = 0.04). These data support the concept of developing peposertib as a radiosensitizer for brain metastases and provide a paradigm for integrating in vitro and pharmacokinetic data to define an optimal radiosensitizing regimen for potent DNA repair inhibitors.

Resection of a Solitary Right Ventricular Metastasis in Oligorecurrent Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC), constituting the predominant manifestation of liver cancer, stands as a formidable medical challenge. The prognosis subsequent to surgical intervention, particularly for individuals presenting with a solitary tumor, relies heavily on the degree of invasiveness. The decision-making process surrounding therapeutic modalities in such cases assumes paramount importance. This case report illuminates a rather unusual clinical scenario. Here, we encounter a patient who, following a disease-free interval, manifested an atypical presentation of HCC, specifically, a solitary cardiac metastasis. The temporal interval of remission adds an additional layer of complexity to the case. Through a multidisciplinary planning process, the decision was made for surgical removal of the metastatic tumor.

Manipulation of Redox Metabolism Using Pharmacologic Ascorbate Opens a Therapeutic Window for Radio-Sensitization by ATM Inhibitors in Colorectal Cancer.

PURPOSE: Ataxia telangiectasia mutated kinase (ATM) inhibitors are potent radiosensitizers that regulate DNA damage responses and redox metabolism, but they have not been translated clinically because of the potential for excess normal tissue toxicity. Pharmacologic ascorbate (P-AscH-; intravenous administration achieving mM plasma concentrations) selectively enhances H2O2-induced oxidative stress and radiosensitization in tumors while acting as an antioxidant and mitigating radiation damage in normal tissues including the bowel. We hypothesized that P-AscH- could enhance the therapeutic index of ATM inhibitor-based chemoradiation by simultaneously enhancing the intended effects of ATM inhibitors in tumors and mitigating off-target effects in adjacent normal tissues. METHODS AND MATERIALS: Clonogenic survival was assessed in human (human colon tumor [HCT]116, SW480, HT29) and murine (CT26, MC38) colorectal tumor lines and normal cells (human umbilical vein endothelial cell, FHs74) after radiation ± DNA repair inhibitors ± P-AscH-. Tumor growth delay was assessed in mice with HCT116 or MC38 tumors after fractionated radiation (5 Gy × 3) ± the ATM inhibitor KU60019 ± P-AscH-. Intestinal injury, oxidative damage, and transforming growth factor ß immunoreactivity were quantified using immunohistochemistry after whole abdominal radiation (10 Gy) ± KU60019 ± P-AscH-. Cell cycle distribution and ATM subcellular localization were assessed using flow cytometry and immunohistochemistry. The role of intracellular H2O2 fluxes was assessed using a stably expressed doxycycline-inducible catalase transgene. RESULTS: KU60019 with P-AscH- enhanced radiosensitization in colorectal cancer models in vitro and in vivo by H2O2-dependent oxidative damage to proteins and enhanced DNA damage, abrogation of the postradiation G2 cell cycle checkpoint, and inhibition of ATM nuclear localization. In contrast, concurrent P-AscH- markedly reduced intestinal toxicity and oxidative damage with KU60019. CONCLUSIONS: We provide evidence that redox modulating drugs, such as P-AscH-, may facilitate the clinical translation of ATM inhibitors by enhancing tumor radiosensitization while simultaneously protecting normal tissues.

Assessment of Gadobutrol Safety in Combination with Ionizing Radiation Using a Preclinical MRI-Guided Radiotherapy Model.

MR-linac technology enhances the precision of therapeutic radiation by clarifying the tumor-normal tissue interface and provides the potential for adaptive treatment planning. Accurate delineation of tumors on diagnostic magnetic resonance imaging (MRI) frequently requires gadolinium-based contrast agents (GBCAs). Despite generally being considered safe, previous literature suggests that GBCAs are capable of contrast-induced acute kidney injury (AKI). It is unclear if the risk for AKI is enhanced when GBCAs are administered concurrently with ionizing radiotherapy. During irradiation, gadolinium may be liberated from its chelator which may induce AKI. The goal of this work was to determine if radiation combined with GBCAs increased the incidence of AKI. Using a preclinical MRI-guided irradiation system, where MRI acquisitions and radiation delivery are performed in rapid succession, tumor-bearing mice with normal kidney function were injected with GBCA and treated with 2, 8 or 18 Gy irradiation. Renal function was assessed on days three and seven postirradiation to assess for AKI. No clinically relevant changes in blood urea nitrogen and creatinine were observed in any combination of GBCA and radiation dose. From these data, we conclude that GBCA in combination with radiation does not increase the risk for AKI in mice. Additional investigation of multiple doses of GBCA administered concurrently with irradiation is warranted to evaluate the risk of chronic kidney injury.

Neoadjuvant Radiotherapy-Related Wound Morbidity in Soft Tissue Sarcoma: Perspectives for Radioprotective Agents.

Historically, patients with localized soft tissue sarcomas (STS) of the extremities would undergo limb amputation. It was subsequently determined that the addition of radiation therapy (RT) delivered prior to (neoadjuvant) or after (adjuvant) a limb-sparing surgical resection yielded equivalent survival outcomes to amputation in appropriate patients. Generally, neoadjuvant radiation offers decreased volume and dose of high-intensity radiation to normal tissue and increased chance of achieving negative surgical margins-but also increases wound healing complications when compared to adjuvant radiotherapy. This review elaborates on the current neoadjuvant/adjuvant RT approaches, wound healing complications in STS, and the potential application of novel radioprotective agents to minimize radiation-induced normal tissue toxicity.

The Effect of Concurrent Stereotactic Body Radiation and Anti-PD-1 Therapy for Recurrent Metastatic Sarcoma.

Patients diagnosed with metastatic sarcoma have limited options for achieving both local and distant tumor control. While SBRT can achieve local control, distant response rates remain low. There is limited evidence demonstrating the safety and efficacy for combining SBRT with concurrent PD-1 checkpoint blockade in metastatic sarcoma. In this prospective case-series, we examined five patients with metastatic sarcoma on pembrolizumab treated concurrently with SBRT from July 1, 2016-October 30, 2018. Acute and chronic toxicity were recorded using Common Terminology Criteria for Adverse Events (CTCAE, version 5.0). SBRT-treated tumor control was assessed using Response Evaluation Criteria in Solid Tumors (RECIST version 1.1). With median follow-up of 14.9 months, three patients with undifferentiated pleomorphic sarcoma, one with intimal, and one with chondroblastic osteosarcoma received SBRT with concurrent pembrolizumab to 10 sites of metastatic disease. No grade 5 toxicities were observed. There was a single incidence of transient grade 4 lymphopenia which resolved without intervention. Grade 3 toxicities included anemia, thrombocytopenia, lymphopenia and colitis. One tumor demonstrated local progression after SBRT, and all others remained stable or with response. In conclusion, combining SBRT with PD-1 inhibition appeared to be safe in this patient population. Expected high rates of treated-tumor local control after SBRT were observed. Two of five patients demonstrated either enhanced local tumor regression, or possible abscopal effect.

Systematic Review of Intensity-Modulated Brachytherapy (IMBT): Static and Dynamic Techniques.

PURPOSE: To systematically review scientific literature on the use of intensity-modulated brachytherapy (IMBT), including static and dynamic shielding approaches, to enhance therapeutic ratio. Studies were evaluated for technique, disease site, dosimetry, applicators, dosimetric calculations, and planning algorithms. Comparisons with standard-of-care brachytherapy techniques, alternative IMBT methods, or both were performed for dose-to-target volumes, organs at risk (OARs), and treatment planning or delivery times. METHODS AND MATERIALS: Inclusion criteria were any peer-reviewed journal articles on IMBT published from January 1, 1980, to January 1, 2019, on PubMed, Google Scholar, Cochrane Library, and EBSCO databases. Two independent investigators reviewed each article for inclusion and exclusion criteria and scope. Data collected on each study included technique, source or shield material, disease site, n of study (n = number of simulated plans/treated patients), dose-to-target/OARs, and planning or delivery times. This review adhered to the Preferred Reporting Items for Systemic reviews and Meta Analyses (PRISMA). RESULTS: Database queries yielded 1734 results, which were reduced to 436 after exclusion criteria and 78 peer-reviewed journal articles after evaluation of scope. Studies per disease site were 31 for cervical; 16 for rectal; 10 for oculocutaneous; 7 for breast; 6 for prostate; and 8 for other, multiple, or no specific disease site. Eighteen studies demonstrated a significant decrease in dose to OARs (5.1%-68.2%), 11 improved treatment planning or delivery times (7.6%-99.7%), and 6 increased target coverage (18.6%-71.6%) relative to standard-of-care or alternative IMBT technique. IMBT consistently decreased dose to OAR compared with the standard of care at the cost of increased planning or delivery times. Innovations in dose calculation or planning algorithms and applicators were capable of ameliorating prolonged treatment intervals. CONCLUSIONS: IMBT techniques improved the therapeutic ratio by reducing OAR doses, facilitating dose escalation, or both. Static-shielding techniques are clinically available as a result of the advent of commercially available heterogeneity-corrected dose-calculation algorithms, whereas dynamic-shielding techniques are still preclinical.

Merkel cell carcinoma in the community setting: a case report.

Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin initially believed to arise from the Merkel cells. In the community setting a general radiation oncologist may only encounter this pathology in a handful of cases over the course of their career. Due to the low incidence of this malignancy, few prospective randomized controlled trials have ever been conducted and therefore guidelines are based on relatively lower levels of evidence upon which the clinical recommendations are made. We discuss the case of a female in her 90s presenting with a classic MCC primary lesion, as well as satellite lesions proximal to both the primary and the draining regional lymph nodes with no evidence of nodal involvement. Here we discuss the presentation, management, treatment planning, underlying pathology, results and sequelae of treatment. We also review new treatment modalities, and the most current staging systems and guidelines.

Low-dose-rate prostate brachytherapy: 4-8 week postimplant prostate-specific antigen a novel predictor of biochemical failure-free survival.

PURPOSE: The purpose of this study was to determine the relationship between patient, disease, and treatment variables and biochemical failure-free survival (bFFS) following low-dose-rate prostate brachytherapy (LDR-BT). METHODS AND MATERIALS: Data from 624 consecutive patients who received LDR-BT for localized prostate cancer between 2002 and 2012 at a single institution were collected for various patient, disease, and treatment characteristics including a 4-8 week postimplant PSA (4-8wkPSA). Subgroup analysis was stratified by risk category and treatment regimen. Analysis was performed using Kaplan-Meier survival curves, Cox proportional hazard ratios (HRs), and receiver-operator characteristic curves. RESULTS: A total of 624 consecutive patients were included with followup time of 4.0 ± 3.1 years. Predictors of bFFS included PSA nadir and 4-8wkPSA (HR = 2.48, p = 0.000 and HR = 1.24, p = 0.000, respectively) for total population. Diabetes mellitus (p = 0.026), chronic obstructive pulmonary disease (p = 0.000), alcohol use (p = 0.024), and age (p = 0.002) were predictors for specific subgroups. Receiver-operator characteristic curves 4-8wkPSA were found to be significant (p = 0.036). CONCLUSION: 4-8wkPSA is a novel predictor of bFFS for patients receiving LDR-BT across several risk categories and treatment regimens with potential clinical utility as a prognostic indicator. Certain comorbidities and exposure histories also demonstrated significant relationships with bFFS including chronic obstructive pulmonary disease, diabetes mellitus, age, alcohol history, proton pump inhibitor use, PSA nadir, and PSA density.