Functional Outcomes and Toxicities Associated with SBRT to Bone Metastases Involving the Joint Space

PURPOSE/OBJECTIVE(S)

Metastatic spread to bone is a common occurrence in advanced malignancies. Stereotactic Body Radiation Therapy (SBRT) is increasingly used for management of bone metastases in both the palliative and oligometastatic settings, especially for radioresistant histologies. Historically, therapeutic radiation to joints has been avoided whenever possible to minimize toxicities such as joint fibrosis and stiffness. Very little data exists to guide the treatment of bone metastases involving or adjacent to the joint space using SBRT. The purpose of this study is to report functional outcomes and toxicities associated with SBRT to metastatic bone lesions involving the joint space.

MATERIALS/METHODS

Patients with solid tumor bone metastases involving the joints of long bones who were treated with SBRT (≥500 cGy/fraction; BED10 ≥37.5) who had ≥30 days follow up were identified from our institutional electronic health record using an IRB approved protocol. Pre-treatment and post-treatment pain assessments and toxicities were collected and scored retrospectively. Toxicities were categorized as acute (≤30 days post treatment) or late (>30 days post-treatment).

RESULTS

Weidentified 40 evaluable patients with 54 lesions treated with SBRT. Lesions treated included those involving the hip (29/54, 54%), shoulder (11/54, 20%), elbow (8/54, 14%), and knee (6/54, 11%). The most common patient histology treated was renal cell carcinoma (13/40, 33%), followed by prostate adenocarcinoma (7/40, 18%), non-small cell lung cancer (4/40, 10%), and breast cancer (4/40, 10%). The remainder (12/40) had other histologies. Median follow up time was 7.7 months (range = 1.3-55.0). Median prescribed dose was 650 cGy/fraction (range = 500-1300 cGy) and most lesions received 4000 cGy in 5 fractions (18/54, 33%). At >30 days, of the 42 sites where pain was reported pre-treatment, 30/42 (71%) had complete or partial pain relief, while 10/42 (24%) experienced no pain relief during available follow up. Patients reported worsening pain after SBRT in 2/54 (3.7%) of treated lesions. Seven of 54 (14.0%) treated lesions led to complaints of joint stiffness requiring physical therapy. A minority of patients developed insufficiency fractures or treatment failures after SBRT requiring surgery (4/54, 7.4%). Three of 54 patients (5.6%) developed symptomatic radiation myositis confirmed on imaging.

CONCLUSION

Toour knowledge, this is the first study to report functional and toxicity outcomes of SBRT to lesions involving the joints of long bones. While SBRT appears to have acceptable toxicities at the doses reported in this analysis, further study is warranted to identify pre-treatment factors predictive of toxicity. Limitations of the study include its small sample size, retrospective nature, and single institution design. Future studies will focus on dosimetric and clinical factors associated with toxicities which may allow for more personalized treatments and assist with informed consent.

Dual Immune Checkpoint Therapy Combined with Radiotherapy Treats Castration-Resistant Prostate Cancer

PURPOSE/OBJECTIVE(S)

Although immune checkpoint inhibitors (ICI) have limited efficacy in clinical studies for metastatic castration-resistant prostate cancer, their combination with radiation therapy (RT) has proven effective in preclinical models. The objective of this project is to test in a syngeneic CRPC mouse model if triple combination anti-CTLA-4 + anti-PD-1 + RT has greater efficacy than dual therapy or monotherapy.

MATERIALS/METHODS

MycCaP prostate tumors were subcutaneously engrafted in wild-type castrated FVB mice. Five treatment groups of 6-9 mice each were compared for survival and tumor graft volume after one-time 0.2 mg intraperitoneal injections of ICI and/or X-ray radiotherapy 20 Gy in 2 treatments given on consecutive days. Treatment groups were: anti-CTLA-4 + anti-PD-1 + RT, anti-CTLA-4 + anti-PD-1, anti-PD-1 + radiotherapy, anti-CTLA-4 alone, and radiotherapy alone. Kaplan-Meier analysis was used to assess the primary survival outcome, and tumor volumes were recorded as secondary outcome.

RESULTS

For mice with castration-resistant prostate cancer, the triple combination therapy of anti-CTLA-4 + anti-PD-1 + RT resulted in the longest median survival of 32 days compared to anti-CTLA-4 alone (11 days, p = 0.0002), radiotherapy alone (22 days, p = 0.0058), and combination anti-CTLA-4 + anti-PD-1 (19.5 days, p = 0.0036). Triple combination therapy had a trend for improved survival compared to combination anti-PD-1 + RT (24 days, p = 0.0529). While monitoring tumor volume measurements, the tumor growth was the slowest for triple combination therapy compared those treated with dual and monotherapies.

CONCLUSION

The triple combination therapy of anti-CTLA-4 + anti-PD-1 + radiotherapy 20 Gy in 2 treatments proved statistically superior in survival and tumor growth delay compared to dual and monotherapies. While clinical studies have tested anti-CTLA-4 + anti-PD-1 for metastatic CRPC, this preclinical model indicates the addition of RT significantly improves in survival and tumor growth delay among FBV mice. This work elucidates the simultaneous use of two immune checkpoint inhibitors in combination with RT has the greatest anti-tumor activity and should be considered in design of clinical trials for metastatic CRPC.

Intravesical oncolytic virotherapy and immunotherapy for non-muscle-invasive bladder cancer mouse model

OBJECTIVES

To test if intravesical instillation of both an anti-programmed cell death protein 1 (PD-1) inhibitor and an oncolytic reovirus would demonstrate a greater effect than either treatment alone, as non-muscle-invasive bladder cancer that is refractory to intravesical bacillus Calmette-Guérin can be treated by systemic anti-PD-1 immunotherapy and we previously demonstrated improved overall survival (OS) with six once-weekly instillations of intravesical anti-PD-1 in a murine model.

MATERIALS AND METHODS

Using an orthotopic syngeneic C3H murine model of MBT2 urothelial bladder cancer, groups of 10 mice were compared between no treatment, intravesical anti-PD-1, intravesical oncolytic reovirus, or intravesical reovirus + anti-PD-1. A single intravesical treatment session was given. The primary outcome was OS, and the secondary outcomes included long-term immunity and tumour-immune profile.

RESULTS

With a median follow-up of 9 months, all mice that received no treatment died with a median survival of 41 days, while the comparison median OS was not reached for reovirus (hazard ratio [HR] 14.4, 95% confidence interval [CI] 3.9-32.6; P < 0.001), anti-PD-1 (HR 28.4, 95% CI 7.0-115.9; P < 0.001), and reovirus + anti-PD-1 (HR 28.4, 95% CI 7.0-115.9; P < 0.001). Monotherapy with anti-PD-1 or reovirus demonstrated no significant differences in survival (P = 0.067). Mass cytometry showed that reovirus + anti-PD-1 treatment enriched monocytes and decreased myeloid-derived suppressor cells, generating an immuno-responsive tumour microenvironment. Depletion of CD8+ T cells eliminated the survival advantage provided by the intravesical treatment.

CONCLUSIONS

Treatment of murine orthotopic bladder tumours with a single instillation of intravesical reovirus, anti-PD-1 antibody, or the combination confers superior survival compared to controls. Tumour-immune microenvironment differences indicated myeloid-derived suppressor cells and CD8+ T cells mediate the treatment response.

Towards differentiation of brain tumor from radiation necrosis using multi-parametric MRI: Preliminary results at 4.7 T using rodent models

BACKGROUND

It remains a clinical challenge to differentiate brain tumors from radiation-induced necrosis in the brain. Despite significant improvements, no single MRI method has been validated adequately in the clinical setting.

METHODS

Multi-parametric MRI (mpMRI) was performed to differentiate 9L gliosarcoma from radiation necrosis in animal models. Five types of MRI methods probed complementary information on different scales i.e., T2 (relaxation), CEST based APT (probing mobile proteins/peptides) and rNOE (mobile macromolecules), qMT (macromolecules), diffusion based ADC (cell density) and SSIFT iAUC (cell size), and perfusion based DSC (blood volume and flow).

RESULTS

For single MRI parameters, iAUC and ADC provide the best discrimination of radiation necrosis and brain tumor. For mpMRI, a combination of iAUC, ADC, and APT shows the best classification performance based on a two-step analysis with the Lasso and Ridge regressions.

CONCLUSION

A general mpMRI approach is introduced to choosing candidate multiple MRI methods, identifying the most effective parameters from all the mpMRI parameters, and finding the appropriate combination of chosen parameters to maximize the classification performance to differentiate tumors from radiation necrosis.

Evaluation of 5 Fraction Stereotactic Body Radiation Therapy (SBRT) for Osseous Renal Cell Carcinoma Metastases

OBJECTIVES

The best fractionation for stereotactic body radiotherapy (SBRT) in renal cell carcinoma (RCC) metastases has not been well defined. In addition, the literature on outcomes using 5-fraction SBRT in the setting of osseous metastases has not been well reported.

MATERIALS AND METHODS

Thirty-nine patients with 69 RCC osseous metastases were treated using 5-fraction SBRT at a single institution using 2 dose-fractionation schemes. Overall survival and local-control (LC) outcomes of the 2 fractionation schemes were studied using Kaplan-Meier curves.

RESULTS

Of the 69 lesions included in the study, 20 were treated with 30 grays (Gy) in 5 fractions and 49 were treated with 40 Gy in 5 fractions. The median age of patients at diagnosis was 58.4 years. The 1-year LC rate for all treated lesions was 85.5% (59/69) with an LC of 90% (18/20) for lesions receiving 30 Gy and 83.7% (41/49) in lesions receiving 40 Gy. There was no statistically significant difference in 1-year LC rate between the 2 fractionation schemes (P-value, 0.553).

CONCLUSIONS

Patients with osseous RCC metastases undergoing 5 fractions of SBRT had favorable LC outcomes. There was no difference in survival or LC between the 40 Gy and 30 Gy treatment arms.

Academic patterns of practice regarding CT simulation scans and radiology review

OBJECTIVE

Currently, there are no consensus guidelines about handling incidental radiological findings on radiotherapy planning CT simulation scans. Retrospective studies analyzing incidental findings on CT simulations show a small, but not insignificant, rate of both oncologic and non-oncologic findings. These findings may have medico-legal, financial, and clinical implications. Given a lack of guidelines, we obtained a formal survey of multiple academic institutions to evaluate how CT simulations are handled in regard to incidental findings.

METHODS

A formal survey was developed consisting of 12 questions related to institutional practices regarding CT simulation scans. From 7/18/21 to 8/27/21 and 5/6/22 to 5/24/22, the survey was administered electronically by REDCap to key personnel at Academic Radiation Oncology Programs identified through the American Society for Radiation Oncology (ASTRO) with inclusion criteria including an active ACGME approved Radiation Oncology residency program.

RESULTS

In total, 88 academic radiation oncology programs were surveyed with total of 45 responses (51%). 1 out of 45 departments who responded has formal guidelines regarding workup of incidental findings. There is variability about sending CT simulation scans for official radiology review if an incidental finding is identified.

CONCLUSIONS

Based on a measurable rate of incidental findings on radiotherapy planning CT simulations and their possible implications, our survey illustrates a likely need for consensus recommendations for handling such findings to improve patient care and safety.

Selective Cell Size MRI Differentiates Brain Tumors from Radiation Necrosis

Brain metastasis is a common characteristic of late-stage lung cancers. High doses of targeted radiotherapy can control tumor growth in the brain but can also result in radiotherapy-induced necrosis. Current methods are limited for distinguishing whether new parenchymal lesions following radiotherapy are recurrent tumors or radiotherapy-induced necrosis, but the clinical management of these two classes of lesions differs significantly. Here, we developed, validated, and evaluated a new MRI technique termed selective size imaging using filters via diffusion times (SSIFT) to differentiate brain tumors from radiotherapy necrosis in the brain. This approach generates a signal filter that leverages diffusion time dependence to establish a cell size-weighted map. Computer simulations in silico, cultured cancer cells in vitro, and animals with brain tumors in vivo were used to comprehensively validate the specificity of SSIFT for detecting typical large cancer cells and the ability to differentiate brain tumors from radiotherapy necrosis. SSIFT was also implemented in patients with metastatic brain cancer and radiotherapy necrosis. SSIFT showed high correlation with mean cell sizes in the relevant range of less than 20 μm. The specificity of SSIFT for brain tumors and reduced contrast in other brain etiologies allowed SSIFT to differentiate brain tumors from peritumoral edema and radiotherapy necrosis. In conclusion, this new, cell size-based MRI method provides a unique contrast to differentiate brain tumors from other pathologies in the brain.

SIGNIFICANCE

This work introduces and provides preclinical validation of a new diffusion MRI method that exploits intrinsic differences in cell sizes to distinguish brain tumors and radiotherapy necrosis.

Radiation Fibrosis After Stereotactic Body Radiation Therapy for Osseous Metastases: A Case Report

Radiation-induced fibrosis is a potentially severe late complication after high-dose radiotherapy. Over the last decade, there has been increasing use of stereotactic body radiation therapy (SBRT) to treat both primary and metastatic malignancies. While there has been evolving evidence of appropriate dose constraints for certain organs receiving hypofractionated radiotherapy, the risk, and appropriate dose constraints to limit the risk of radiation-induced muscle fibrosis are poorly defined. In this report, two patients are presented who underwent SBRT for osseous oligometastatic renal cell carcinoma. While the treatment was well-tolerated with no acute toxicities and complete local control of the metastasis, both patients experienced late toxicity of radiation-induced fibrosis in the adjacent musculature. In both cases, toxicity was nonresponsive to medical interventions and was severe enough to require surgical resection of the affected tissue. Following surgery, both patients reported improved pain relief and mobility. Further studies are needed to explore the dose constraints that may reduce the risk of radiation-induced muscle fibrosis in five-fraction treatment.

Rodent Model of Brain Radionecrosis using Clinical LINAC-based Stereotactic Radiosurgery

Purpose

Methods and Materials

Results

Conclusions

Radiopharmaceuticals as Novel Immune System Tracers

Immune checkpoint inhibitors (ICIs) have transformed the treatment paradigms for multiple cancers. However, ICI therapy often fails to generate measurable and sustained antitumor responses, and clinically meaningful benefits remain limited to a small proportion of overall patients. A major obstacle to development and effective application of novel therapeutic regimens is optimized patient selection and response assessment. Noninvasive imaging using novel immunoconjugate radiopharmaceuticals (immuno–positron emission tomography and immuno-single-photon emission computed tomography) can assess for expression of cell surface immune markers, such as programmed cell death protein ligand-1 (PD-L1), akin to a virtual biopsy. This emerging technology has the potential to provide clinicians with a quantitative, specific, real-time evaluation of immunologic responses relative to cancer burden in the body. We discuss the rationale for using noninvasive molecular imaging of the programmed cell death protein-1 and PD-L1 axis as a biomarker for immunotherapy and summarize the current status of preclinical and clinical studies examining PD-L1 immuno–positron emission tomography. The strategies described in this review provide insight for future clinical trials exploring the use of immune checkpoint imaging as a biomarker for both ICI and radiation therapy, and for the rational design of combinatorial therapeutic regimens.

Patient Reported Quality of Life Outcomes After Definitive Radiation Therapy With Absorbable Spacer Hydrogel for Prostate Cancer

Purpose

SpaceOAR is a device approved for conventional radiation in prostate cancer. We sought to observe prospectively how SpaceOAR Hydrogel effected quality of life and dosimetry to organs at risk at our institution.

Methods and Materials

We prospectively enrolled patients with low risk or favorable-intermediate risk localized prostate cancer. Baseline Expanded Prostate Cancer Index Composite (EPIC-26) scores along with baseline American Urology Association Symptom Index (AUA-SI) scores were collected. SpaceOAR was placed for all patients who then received stereotactic body radiation therapy, low dose rate brachytherapy, conventionally fractionated radiation therapy, or moderately hypofractionated radiation therapy. We evaluated postimplant dosimetry to critical structures, and prospectively collected follow-up EPIC-26 and AUA-SI scores. We performed a repeated measures analysis of variance to compare patient-specific responses and correlated survey data with dosimetric metrics by generating linear regression models.

Results

We enrolled 59 patients in this study with a median follow-up of 366 days (interquartile range, 507). At final follow-up, the "?>prostate-specific antigen had a significant decline compared with baseline (P < .0001). There were no grade 3 toxicities on treatment. There were no significant changes in the AUA-SI score (P = .69) at final follow-up compared with baseline, nor was there any change in EPIC-26 domain scores (P = .19) during the course of the study period. There were no significant associations between AUA scores and EPIC-26 scores and the dose to the rectum, bladder, or urethra with the exception being dose to the 2 mL rectum correlated with decline in EPIC-26 rectal score (β, −0.002; P = .006). Patient-reported declines in bowel domains were less than previously reported data.

Conclusions

Use of SpaceOAR results in favorable dosimetry to the organs at risk and portends excellent short-term quality of life as measured by the association with the patient reported outcome measures. Longer-term follow-up is ongoing and necessary to assess the long-term effect and association of the hydrogel.

Targeting for stereotactic radiosurgical thalamotomy based on tremor treatment response

OBJECTIVE

Stereotactic radiosurgery (SRS) treats severe, medically refractory essential tremor and tremor-dominant Parkinson disease. However, the optimal target for SRS treatment within the thalamic ventral intermediate nucleus (VIM) is not clearly defined. This work evaluates the precision of the physician-selected VIM target, and determines the optimal SRS target within the VIM by correlation between early responders and nonresponders.

METHODS

Early responders and nonresponders were assessed retrospectively by Elements Basal Ganglia Atlas autocontouring of the VIM on the pre-SRS-treatment 1-mm slice thickness T1-weighted MRI and correlating the center of the post-SRS-treatment lesion. Using pre- and posttreatment diffusion tensor imaging, the fiber tracking package in the Elements software generated tremor-related tracts from autosegmented motor cortex, thalamus, red nucleus, and dentate nucleus. Autocontouring of the VIM was successful for all patients.

RESULTS

Among 23 patients, physician-directed SRS targets had a medial-lateral target range from +2.5 mm to -2.0 mm from the VIM center. Relative to the VIM center, the SRS isocenter target was 0.7-0.9 mm lateral for 6 early responders and 0.9-1.1 mm medial for 4 nonresponders (p = 0.019), and without differences in the other dimensions: 0.2 mm posterior and 0.6 mm superior. Dose-volume histogram analyses for the VIM had no significant differences between responders and nonresponders between 20 Gy and 140 Gy, mean or maximum dose, and dose to small volumes. Tractography data was obtained for 4 patients.

CONCLUSIONS

For tremor control in early responders, the Elements Basal Ganglia Atlas autocontour for the VIM provides the optimal SRS target location that is 0.7-0.9 mm lateral to the VIM center.

Noninvasive Thalamotomy for Refractory Tremor by Frameless Radiosurgery

OBJECTIVE

We sought to determine whether a more widely accessible, non-invasive frameless approach to radiosurgical thalamotomy would improve objective measures of refractory essential or parkinsonian tremor without added toxicity compared to reports of frame-based radiosurgery.

METHODS

We conducted a single-arm pilot observational prospective trial of adult patients with essential or parkinsonian tremor from 2013 to 2019 and report results at one-year follow-up. Patients were treated with frameless unilateral radiosurgical ablation of the thalamic ventral intermediate nucleus to a maximum dose of 160 Gy. Treatment response was measured by the Fahn-Tolosa-Marin (FTM) tremor rating scale and the Quality of Life in Essential Tremor or Parkinson's Disease Questionnaire obtained prior to treatment and at 3, 6, 9, and 12 months.

RESULTS

Thirty-three patients, including 23 with essential tremor and 10 with Parkinson's disease, were enrolled. Overall treatment response rate per FTM was 83% (n=15/18) at 6 months. There was a marked improvement in tremor, with average total FTM reduction of 21% at 3 months (from 46 to 30 points, p=0.003) and 41% at 6 months (from 46 to 24 points, p=0.001). At 6 months, functional decline had regressed by 54% (from 15 to 7 points, p=0.001). Quality of life improved by 57% (p=0.001) at 6 months in patients with essential tremor, and patients with Parkinson's Disease had unchanged quality of life. At one-year follow-up, grade 2 neurologic adverse events were observed in 6% (n=2/33) of patients without any grade ≥ 3 events.

CONCLUSION

Noninvasive, frameless radiosurgical thalamotomy may be a feasible treatment for patients with refractory tremor and demonstrates short-term safety at one-year follow-up. This pilot study provides promising preliminary descriptions of efficacy, and definitive estimates of long-term safety and benefit require further study with longer follow-up.

Intravesical Anti-PD-1 Immune Checkpoint Inhibition Treats Urothelial Bladder Cancer in a Mouse Model

PURPOSE

Nonmuscle-invasive bladder cancer is treated by resection within the bladder and bladder instillment with bacillus Calmette-Guérin or chemotherapy. For bacillus Calmette-Guérin-refractory disease, systemic anti-PD-1 (programmed cell death protein 1) immune checkpoint inhibition is a treatment. Our aim is to test whether intravesical instillment with anti-PD-1 inhibitor treats localized bladder cancer as effectively as systemic administration.

MATERIALS AND METHODS

We investigated an orthotopic mouse model of urothelial bladder cancer using MBT2 cells instilled into the bladders of syngeneic, wild-type C3H mice. Groups of 10 mice received each treatment for comparison of intravesical anti-PD-1, intraperitoneal anti-PD1, and intravesical chemotherapy. The primary outcome was overall survival and secondary outcomes included long-term immunity and toxicity.

RESULTS

Anti-PD-1 administered by bladder instillment (intravesical route) successfully treats localized bladder cancer and has similar overall survival to anti-PD-1 by systemic route. Anti-PD-1 by either route provides a significant survival advantage over control antibody. Anti-PD-1 increases CD8+ cell infiltration in tumors, particularly when administered intravesically. Antibody treatment avoids toxicity observed for intravesical chemotherapy. Mice who cleared their tumors after initial treatment were rechallenged with tumor engraftment 3-9 months later without any additional treatment. Initial anti-PD-1-treated mice did not grow tumors when rechallenged, which suggests long-term immunity exists, but initial mitomycin-treated mice readily grew tumors indicating no immunity occurred by chemotherapy treatment.

CONCLUSIONS

Intravesical administration of anti-PD-1 is a promising treatment route for localized bladder cancer, with comparable overall survival to systemic anti-PD-1 in this mouse model. Intravesical anti-PD-1 increases CD8+ T cells in treated tumors and long-term immunity was seen to tumor rechallenge.

Monte Carlo study on dose distributions from total skin electron irradiation therapy (TSET)

Total skin electron therapy (TSET) has been used to treat mycosis fungoides since the 1950s. Practitioners of TSET rely on relatively crude, phantom-based point measurements for commissioning and treatment plan dosimetry. Using Monte Carlo simulation techniques, this study presents whole-body dosimetry for a patient receiving rotational, dual-field TSET. The Monte Carlo codes, BEAMnrc/DOSXYZnrc, were used to simulate 6 MeV electron beams to calculate skin dose from TSET. Simulations were validated with experimental measurements. The rotational dual-field technique uses extended source-to-surface distance with an acrylic beam degrader between the patient and incident beams. Simulations incorporated patient positioning: standing on a platform that rotates during radiation delivery. Resultant patient doses were analyzed as a function of skin depth-dose coverage and evaluated using dose-volume-histograms (DVH). Good agreement was obtained between simulations and measurements. For a cylinder with a 30 cm diameter, the depths that dose fell to 50% of the surface dose was 0.66 cm, 1.15 cm and 1.42 cm for thicknesses of 9 mm, 3 mm and without an acrylic scatter plate, respectively. The results are insensitive to cylinder diameter. Relatively uniform skin surface dose was obtained for skin in the torso area although large dose variations (>25%) were found in other areas resulting from partial beam shielding of the extremities. To achieve 95% mean dose to the first 5 mm of skin depth, the mean dose to skin depth of 5-10 mm and depth of 10-15 mm from the skin surface was 74% (57%) and 50% (25%) of the prescribed dose when using a 3mm (9 mm) thickness scatter plate, respectively. As a result of this investigation on patient skin dose distributions we changed our patient treatments to use a 3 mm instead of a 9 mm thickness Acrylic scatter plate for clinically preferred skin depth dose coverage.

Prospective observational trial of low-dose skin electron beam therapy in mycosis fungoides using a rotational technique

INTRODUCTION

Low-dose total skin electron beam therapy provides a durable treatment response for skin lesions caused by cutaneous T-cell lymphoma. We prospectively assessed the durability of response and quality of life for patients receiving low-dose total skin electron beam therapy using a novel rotational technique and dosing regimen.

METHODS

Patients completed baseline Skindex-29 quality-of-life surveys and had baseline Modified Severity-Weighted Assessment Tool score recorded. Patients received 12 Gy in 12 fractions with a dual-field rotational technique. The primary outcome was overall response rate, with the secondary outcomes being time to treatment response, duration of clinical benefit, and quality-of-life change.

RESULTS

We enrolled 20 patients and recorded an overall response rate of 90%. The median time to treatment response was 6.5 weeks. The baseline Modified Severity-Weighted Assessment Tool score was 55.6 and it declined to a median of 2.2 at last follow-up (P < .001). The median duration of clinical benefit was 21 months. There was a decline in the Skindex-29 total score and every subdomain when each follow-up visit was compared (P = .004).

CONCLUSIONS

This prospective study demonstrated a very high overall response rate and improvement in skin-related quality of life. Low-dose rotational total skin electron beam therapy can be implemented routinely in clinical practice.

An autoimmune-based, paraneoplastic neurologic syndrome following checkpoint inhibition and concurrent radiotherapy for merkel cell carcinoma: case report

PURPOSE

Merkel cell carcinoma is highly sensitive to both radiation and immunotherapy. Moreover, concurrent radioimmunotherapy may capitalize on anti-tumor immune activity and improve Merkel cell treatment response, although an enhanced immune system may cross-react with native tissues and lead to significant sequelae.

METHODS

Here we present a case study of a patient with metastatic Merkel cell carcinoma treated with radiotherapy concurrent with pembrolizumab.

RESULTS

After radioimmunotherapy, the patient developed sensory neuropathy, visual hallucinations, and mixed motor neuron findings. Neurologic dysfunction progressed to profound gastrointestinal dysmotility necessitating parenteral nutrition and intubation with eventual expiration.

CONCLUSION

This case represents a unique autoimmune paraneoplastic neurologic syndrome, likely specific to neuroendocrine tumors and motivated by concurrent radioimmunotherapy. Recognition of the potential role of radioimmunotherapy may provide an advantage in anticipating these severe sequelae.

Intensity-Modulated Radiotherapy is Superior to Three-Dimensional Conformal Radiotherapy in the Trimodality Management of Muscle-Invasive Bladder Cancer with Daily Cone Beam Computed Tomography Optimization

Objective

Intensity modulated radiation therapy (IMRT) using a volumetric-modulated arc therapy technique may offer dosimetric and clinical benefits compared to the historical standard of care 3D-conformal radiotherapy (3D-CRT) in definitive treatment of bladder cancer. We hypothesized that IMRT with CBCT would reduce dose to the rectum, bowel, and bladder compared to 3D-CRT.

Methods

We reviewed nineteen patients treated with maximal transurethral resection of bladder tumor followed by concurrent chemotherapy with IMRT. All patients received 45 Gy to the entire empty bladder followed by 19.8 Gy tumor boost treated with full bladder. 3D-CRT treatment plans were created for the same prescription. Paired t-test or Wilcoxon matched-pairs signed rank test analyzed dosimetry and bladder volumes.

Results

The rectum and bowel V40, V45, V50, V55, and V60 were reduced by over 50% in the IMRT plans compared to 3D-CRT (p<0.0001). IMRT also reduced volume of bladder irradiated compared to 3D-CRT (p<0.01). After CBCT, patients were likely to undergo clinically significant shifts ≥ 0.5 cm before boost delivery (p=0.001). Bladder volumes were significantly lower during boost treatments compared to pre-treatment simulation (p=0.002). There were 4 (21%) grade 3 genitourinary toxicities and 1 (5%) grade 3 gastrointestinal toxicity.

Conclusion

IMRT is superior to 3D-CRT for bladder cancer and spares dose to bowel, rectum, and bladder with improved acute toxicity compared to published clinical literature. For boost treatment, daily full bladder volume and positioning are not always reproducible, supporting the need for CBCT for optimal localization of the primary bladder tumor.

Combination immunotherapy and radiotherapy causes an abscopal treatment response in a mouse model of castration resistant prostate cancer

BACKGROUND

Prostate cancer is poorly responsive to immune checkpoint inhibition, yet a combination with radiotherapy may enhance the immune response. In this study, we combined radiotherapy with immune checkpoint inhibition (iRT) in a castration-resistant prostate cancer (CRPC) preclinical model.

METHODS

Two Myc-CaP tumor grafts were established in each castrated FVB mouse. Anti-PD-1 or anti-PD-L1 antibodies were given and one graft was irradiated 20 Gy in 2 fractions.

RESULTS

In CRPC, a significant increase in survival was found for radiation treatment combined with either anti-PD-1 or anti-PD-L1 compared to monotherapy. The median survival for anti-PD-L1 alone was 13 days compared to 30 days for iRT (p = 0.0003), and for anti-PD-1 alone was 21 days compared to 36 days for iRT (p = 0.0009). Additional treatment with anti-CD8 antibody blocked the survival effect. An abscopal treatment effect was observed for iRT in which the unirradiated graft responded similarly to the irradiated graft in the same mouse. At 21 days, the mean graft volume for anti-PD-1 alone was 2094 mm³ compared to iRT irradiated grafts 726 mm³ (p = 0.04) and unirradiated grafts 343 mm³ (p = 0.0066). At 17 days, the mean graft volume for anti-PD-L1 alone was 1754 mm³ compared to iRT irradiated grafts 284 mm³ (p = 0.04) and unirradiated grafts 556 mm³ (p = 0.21). Flow cytometry and immunohistochemistry identified CD8+ immune cell populations altered by combination treatment in grafts harvested at the peak effect of immunotherapy, 2-3 weeks after starting treatment.

CONCLUSIONS

These data provide preclinical evidence for the use of iRT targeting PD-1 and PD-L1 in the treatment of CRPC. Immune checkpoint inhibition combined with radiotherapy treats CPRC with significant increases in median survival compared to drug alone: 70% longer for anti-PD-1 and 130% for anti-PD-L1, and with an abscopal treatment effect.

PRECIS

Castration-resistant prostate cancer in a wild-type mouse model is successfully treated by X-ray radiotherapy combined with PD-1 or PD-L1 immune checkpoint inhibition, demonstrating significantly increased median overall survival and robust local and abscopal treatment responses, in part mediated by CD8 T-cells.

Radiosensitization by enzalutamide for human prostate cancer is mediated through the DNA damage repair pathway

Radiation therapy is often combined with androgen deprivation therapy in the treatment of aggressive localized prostate cancer. However, castration-resistant disease may not respond to testosterone deprivation approaches. Enzalutamide is a second-generation anti-androgen with high affinity and activity that is used for the treatment of metastatic disease. Although radiosensitization mechanisms are known to be mediated through androgen receptor activity, this project aims to uncover the detailed DNA damage repair factors influenced by enzalutamide using multiple models of androgen-sensitive (LNCaP) and castration-resistant human prostate cancer (22Rv1 and DU145). Enzalutamide is able to radiosensitize both androgen-dependent and androgen-independent human prostate cancer models in cell culture and xenografts in mice, as well as a treatment-resistant patient-derived xenograft. The enzalutamide-mediated mechanism of radiosensitization includes delay of DNA repair through temporal prolongation of the repair factor complexes and halting the cell cycle, which results in decreased colony survival. Altogether, these findings support the use of enzalutamide concurrently with radiotherapy to enhance the treatment efficacy for prostate cancer.

Radiation-associated epithelial-myoepithelial carcinoma among five secondary malignancies: A case report and review of literature

BACKGROUND

Epithelial-myoepithelial carcinoma (EMC) is a rare, low-grade, malignant tumor that constitutes less than one percent of all salivary gland tumors. To date, only one other case report has described radiation-associated EMC in the English language medical literature.

CASE SUMMARY

In this report, we describe the case of a 56-year-old male patient who presented with a neck mass diagnosed as EMC of the left submandibular gland approximately 30 years after mantle field radiation and chemotherapy for Hodgkin lymphoma. Treatment included resection, re-resection with nodal dissection, and adjuvant chemoradiotherapy. This patient was also diagnosed with 4 other secondary malignancies, including stage IV diffuse large B cell lymphoma in the abdomen with subsequent brain metastases, low-grade neuroendocrine carcinoma of the lung, Hurthle cell adenoma, and small B cell lymphoma before the patient expired. This case provides important information regarding the pathology, clinical sequelae, and management of a patient diagnosed with radiation-associated EMC amidst four concurrent malignancies.

CONCLUSION

Further investigation is needed on the efficacy of adjuvant radiotherapy in EMC, especially atypical EMC.

Linear Accelerator-Based Stereotactic Radiosurgery for Cranial Intraparenchymal Metastasis of a Malignant Peripheral Nerve Sheath Tumor: Case Report and Review of the Literature

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are rare, aggressive soft tissue sarcomas. MPNST intracranial metastasis is exceedingly rare with only 22 documented cases in the literature and, to our knowledge, only 1 case with intraparenchymal brain metastasis. Most have been managed surgically; however, 2 documented cases were treated with Gamma Knife radiosurgery. Excluding this case report, there are no other documented cases of linear accelerator-based stereotactic radiosurgery (SRS) to treat MPNST brain metastasis.

CASE DESCRIPTION

A 41-year-old man with MPNST of the lung initially underwent tumor resection. He developed multiple systemic metastases that were managed with directed radiation therapy. A parietal brain metastasis was treated with linear accelerator-based SRS. Following SRS therapy, the patient was treated with a tropomyosin receptor kinase inhibitor. Complete resolution of brain metastasis was seen on brain magnetic resonance imaging 5 months after treatment with SRS. At 11 months after SRS, there was no evidence of recurrence or progression of the intraparenchymal disease. The patient continued to have stable extracranial disease on his ninth cycle of systemic treatment.

CONCLUSIONS

This report provides important insights into efficacy of linear accelerator-based SRS to treat MPNST brain metastases.

Margin of error for a frameless image guided radiosurgery system: Direct confirmation based on posttreatment MRI scans

PURPOSE

To report on radiosurgery delivery positioning accuracy in the treatment of tremor patients with frameless image guided radiosurgery using the linear accelerator (LINAC) based ExacTrac system and to describe quality assurance (QA) procedures used.

METHODS AND MATERIALS

Between 2010 and 2015, 20 patients underwent radiosurgical thalamotomy targeting the ventral intermediate nucleus for the treatment of severe tremor. The median prescription dose was 140 Gy (range, 120-145 Gy) in a single fraction. The median maximum dose was 156 Gy (range, 136-162 Gy). All treatment planning was performed with the iPlan system using a 4-mm circular cone with multiple arcs. Before each treatment, QA procedures were performed, including the imaging system. As a result of the extremely high dose delivered in a single fraction, a well-defined circular mark developed on the posttreatment magnetic resonance imaging (MRI). Eight of these 20 patients were selected to evaluate treatment localization errors because their circular marks were available in posttreatment MRI. In this study, the localization error is defined as the distance between the center of the intended target and the center of the posttreatment mark.

RESULTS

The mean error of distance was found to be 1.1 mm (range, 0.4-1.5 mm). The mean errors for the left-right, anteroposterior, and superoinferior directions are 0.5 mm, 0.6 mm, and 0.7 mm, respectively.

CONCLUSIONS

The result reported in this study includes all tremor patients treated at our institution when their posttreatment MRI data were available for study. It represents a direct confirmation of target positioning accuracy in radiosurgery with a LINAC-based frameless system and its limitations. This level of accuracy is only achievable with an appropriate QA program in place for a LINAC-based frameless radiosurgery system.

PIM kinase inhibitor AZD1208 for treatment of MYC-driven prostate cancer

BACKGROUND

PIM1 kinase is coexpressed with c-MYC in human prostate cancers (PCs) and dramatically enhances c-MYC-induced tumorigenicity. Here we examine the effects of a novel oral PIM inhibitor, AZD1208, on prostate tumorigenesis and recurrence.

METHODS

A mouse c-MYC/Pim1-transduced tissue recombination PC model, Myc-CaP allografts, and human PC xenografts were treated with AZD1208 (n = 5-11 per group). Androgen-sensitive and castrate-resistant prostate cancer (CRPC) models were studied as well as the effects of hypoxia and radiation. RNA sequencing was used to analyze drug-induced gene expression changes. Results were analyzed with χ(2) test. Student's t test and nonparametric Mann-Whitney rank sum U Test. All statistical tests were two-sided.

RESULTS

AZD1208 inhibited tumorigenesis in tissue recombinants, Myc-CaP, and human PC xenograft models. PIM inhibition decreased c-MYC/Pim1 graft growth by 54.3 ± 39% (P < .001), decreased cellular proliferation by 46 ± 14% (P = .016), and increased apoptosis by 326 ± 170% (P = .039). AZD1208 suppressed multiple protumorigenic pathways, including the MYC gene program. However, it also downregulated the p53 pathway. Hypoxia and radiation induced PIM1 in prostate cancer cells, and AZD1208 functioned as a radiation sensitizer. Recurrent tumors postcastration responded transiently to either AZD1208 or radiation treatment, and combination treatment resulted in more sustained inhibition of tumor growth. Cell lines established from recurrent, AZD1208-resistant tumors again revealed downregulation of the p53 pathway. Irradiated AZD1208-treated tumors robustly upregulated p53, providing a possible mechanistic explanation for the effectiveness of combination therapy. Finally, an AZD1208-resistant gene signature was found to be associated with biochemical recurrence in PC patients.

CONCLUSIONS

PIM inhibition is a potential treatment for MYC-driven prostate cancers including CRPC, and its effectiveness may be enhanced by activators of the p53 pathway, such as radiation.

Eosinophilic pleural effusion complicating allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is primarily a disease of patients with cystic fibrosis or asthma, who typically present with bronchial obstruction, fever, malaise, and expectoration of mucus plugs. We report a case of a young man with a history of asthma who presented with cough, left-sided pleuritic chest pain and was found to have lobar atelectasis and an eosinophilic, empyematous pleural effusion. Bronchoscopy and sputum cultures grew Aspergillus fumigatus, and testing confirmed strong allergic response to this mold, all consistent with a diagnosis of ABPA. This novel and unique presentation of ABPA expands on the differential diagnosis of eosinophilic pleural effusions.

Characteristics of Epstein-Barr virus envelope protein gp42

Epstein-Barr virus (EBV) glycoprotein 42 (gp42) is a membrane protein essential for fusion and entry of EBV into host B-lymphocytes. Gp42 is a member of the protein-fold family C-type lectin or lectin-like domains (CLECT or CTLD) and specifically is classified as a natural-killer receptor (NKR)-like CLECT. Literature review and phylogenetic comparison show that EBV gp42 shares a common structure with other NKR-like CLECTs and possibly with many viral CTLDs, but does not appear to exhibit some common binding characteristics of many CTLDs, such as features required for calcium binding. The flexible N-terminal region adjacent to the CTLD fold is important for binding to other EBV glycoproteins and for a cleavage site that is necessary for infection of host cells. From structural studies of gp42 unbound and bound to receptor and extensive mutational analysis, a general model of how gp42 triggers membrane fusion utilizing both the flexible N-terminal region and the CTLD domain has emerged.

Structure of Epstein-Barr virus glycoprotein 42 suggests a mechanism for triggering receptor-activated virus entry

Epstein-Barr virus requires glycoproteins gH/gL, gB, and gp42 to fuse its lipid envelope with B cells. Gp42 is a type II membrane protein consisting of a flexible N-terminal region, which binds gH/gL, and a C-terminal lectin-like domain that binds to the B-cell entry receptor human leukocyte antigen (HLA) class II. Gp42 triggers membrane fusion after HLA binding, a process that requires simultaneous binding to gH/gL and a functional hydrophobic pocket in the lectin domain adjacent to the HLA binding site. Here we present the structure of gp42 in its unbound form. Comparisons to the previously determined structure of a gp42:HLA complex reveals additional N-terminal residues forming part of the gH/gL binding site and structural changes in the receptor binding domain. Although the core of the lectin domain remains similar, significant shifts in two loops and an alpha helix bordering the essential hydrophobic pocket suggest a structural mechanism for triggering fusion.

Binding-site interactions between Epstein-Barr virus fusion proteins gp42 and gH/gL reveal a peptide that inhibits both epithelial and B-cell membrane fusion

Herpesviruses require membrane-associated glycoproteins gB, gH, and gL for entry into host cells. Epstein-Barr virus (EBV) gp42 is a unique protein also required for viral entry into B cells. Key interactions between EBV gp42 and the EBV gH/gL complex were investigated to further elucidate their roles in membrane fusion. Deletion and point mutants within the N-terminal region of gp42 revealed residues important for gH/gL binding and membrane fusion. Many five-residue deletion mutants in the N-terminal region of gp42 that exhibit reduced membrane fusion activity retain binding with gH/gL but map out two functional stretches between residues 36 and 96. Synthetic peptides derived from the gp42 N-terminal region were studied in in vitro binding experiments with purified gH/gL and in cell-cell fusion assays. A peptide spanning gp42 residues 36 to 81 (peptide 36-81) binds gH/gL with nanomolar affinity, comparable to full-length gp42. Peptide 36-81 efficiently inhibits epithelial cell membrane fusion and competes with soluble gp42 to inhibit B-cell fusion. Additionally, this peptide at low nanomolar concentrations inhibits epithelial cell infection by intact virus. Shorter gp42 peptides spanning the two functional regions identified by deletion mutagenesis had little or no binding to soluble gH/gL and were also unable to inhibit epithelial cell fusion, nor could they complement gp42 deletion mutants in B-cell fusion. These studies identify key residues of gp42 that are essential for gH/gL binding and membrane fusion activation, providing a nanomolar inhibitor of EBV-mediated membrane fusion.

Soluble Epstein-Barr virus glycoproteins gH, gL, and gp42 form a 1:1:1 stable complex that acts like soluble gp42 in B-cell fusion but not in epithelial cell fusion

Epstein-Barr virus (EBV) is a herpesvirus that infects cells by fusing its lipid envelope with the target cell membrane. The fusion process requires the actions of viral glycoproteins gH, gL, and gB for entry into epithelial cells and additionally requires gp42 for entry into B cells. To further study the roles of these membrane-associated glycoproteins, purified soluble forms of gp42, gH, and gL were expressed that lack the membrane-spanning regions. The soluble gH/gL protein complex binds to soluble gp42 with high affinity, forming a stable heterotrimer with 1:1:1 stoichiometry, and this complex is not formed by an N-terminally truncated variant of gp42. The effects of adding soluble gp42, gH/gL, and gH/gL/gp42 were examined with a virus-free cell-cell fusion assay. The results demonstrate that, in contrast to gp42, membrane fusion does not proceed with secreted gH/gL. The addition of soluble gH/gL does not inhibit or enhance B-cell or epithelial cell fusion when membrane-bound gH/gL, gB, and gp42 are present. However, the soluble gH/gL/gp42 complex does activate membrane fusion with B cells, similarly to soluble gp42, but it does not inhibit fusion with epithelial cells, as observed for gp42 alone. A gp42 peptide, derived from an N-terminal segment involved in gH/gL interactions, binds to soluble gH/gL and inhibits EBV-mediated epithelial cell fusion, mimicking gp42. These observations reveal distinct functional requirements for gH/gL and gp42 complexes in EBV-mediated membrane fusion.

X-ray crystal structure of an anti-Buckminsterfullerene antibody fab fragment: biomolecular recognition of C(60)

We have prepared a monoclonal Buckminsterfullerene specific antibody and report the sequences of its light and heavy chains. We also show, by x-ray crystallographic analysis of the Fab fragment and by model building, that the fullerene binding site is formed by the interface of the antibody light and heavy chains. Shape-complementary clustering of hydrophobic amino acids, several of which participate in putative stacking interactions with fullerene, form the binding site. Moreover, an induced fit mechanism appears to participate in the fullerene binding process. Affinity of the antibody-fullerene complex is 22 nM as measured by competitive binding. These findings should be applicable not only to the use of antibodies to assay and direct potential fullerene-based drug design but could also lead to new methodologies for the production of fullerene derivatives and nanotubes as well.