Effect of prescription isodose line on tissue sparing in linear accelerator-based stereotactic radiosurgery treating multiple brain metastases using dynamic conformal arcs.

PURPOSE: Linear accelerator-based stereotactic radiosurgery (SRS) has become a mainstay for simultaneous management of multiple intracranial targets. Recent improvements in treatment planning systems (TPS) have enabled treatment of multiple brain metastases using dynamic conformal arcs (DCA) and a single treatment isocenter. However, as the volume of healthy tissue receiving at least 12 Gy (V12) is linked to the probability of developing radionecrosis, balancing target coverage while minimizing V12 is a critical factor affecting SRS plan quality. Current TPS allow users to adjust various parameters influencing plan optimization. The purpose of this work is to quantify the effect of negative margins on V12 for cranial SRS plans managing multiple brain metastases. METHODS: Using the Brainlab Elements v3.0 TPS (Brainlab, Munich, Germany), we calculated V10, V12, V15, monitor units, and conformity index for seventeen SRS plans treating 2-10 metastases on our Elekta Versa HD (Elekta, Stockholm, Sweden) linear accelerator. We compared plans optimized using 70%-90% prescription isodose lines (IDL) in 5% increments. RESULTS: Irrespective of the number of treated metastases, optimization at a lower prescription IDL reduced V10, V12, and V15 and increased MU compared to the 90% IDL (p < 0.01). However, comparing the 70% and 75% IDL optimizations, there was little difference in tissue sparing. The conformity index showed no consistent trends at different IDLs due to a significant spread in case data. CONCLUSION: For our plans treating up to 10 metastases, diminishing returns for tissue sparing at IDLs below 80% paired with increasing treatment MU and dosimetric hot spot made optimization at lower IDLs less favorable. In our clinic, after consulting with a physician, it was determined that optimization at the 80% IDL achieved the best balance of V12, treatment MU, and maximum dose. Clinics implementing LINAC-based SRS programs may consider using similar evaluations to develop their own clinical protocols.

Clinical Outcomes in Patients with Recurrent Glioblastoma Treated with Proton Beam Therapy Reirradiation: Analysis of the Multi-Institutional Proton Collaborative Group Registry.

PURPOSE: As a means of limiting normal tissue toxicity, proton-beam therapy (PBT) is an emerging radiation modality for glioblastoma (GBM) reirradiation. However, data for recurrent GBM treated with PBT reirradiation is limited. Therefore, we analyzed treatment patterns, toxicities, and clinical outcomes of patients with recurrent GBM treated with PBT reirradiation using the multi-institutional Proton Collaborative Group registry. METHODS AND MATERIALS: Prospectively collected data for patients with recurrent GBM who underwent PBT while enrolled in Proton Collaborative Group study 01-009 (NCT01255748) were analyzed. We evaluated overall survival (OS), progression-free survival (PFS), and toxicity. Toxicities were scored per the Common Terminology Criteria for Adverse Events, version 4.0. Descriptive statistics were used to report patient, tumor, and treatment characteristics. Multivariable analyses (MVA) for toxicity were conducted using logistic regression. The Kaplan-Meier method was used to calculate OS and PFS. MVA for OS and PFS was conducted using Cox proportional-hazards models. The SAS statistical software was used for the analysis. RESULTS: We identified 45 recurrent patients with GBM who underwent PBT reirradiation between 2012 and 2018. The median time between initial GBM diagnosis and recurrence was 20.2 months. The median follow-up time from PBT reirradiation was 10.7 months. Median PFS was 13.9 months (95% confidence interval [CI], 8.23-20.0 months) and median OS was 14.2 months (95% CI, 9.6-16.9 months) after PBT reirradiation. One patient experienced an acute grade 3 toxicity, 4 patients experienced late grade 3 toxicity (no grade ≥4 toxicities). MVA revealed that prior surgery was associated with a 91.3% decreased hazard of death (hazard ratio: 0.087; 95% CI, 0.02-0.42; P < .01). No explanatory variables were associated with PFS or grade 3 toxicities. CONCLUSIONS: This is the largest series to date reporting outcomes for PBT reirradiation of patients with recurrent GBM. Our analysis indicates that PBT is well tolerated and offers efficacy rates comparable with previously reported photon reirradiation.

Feasibility and Outcome of Routine Use of Concurrent Chemoradiation in HIV-positive Patients With Squamous Cell Anal Cancer.

OBJECTIVES: Clinical concerns about hematologic toxicities in human immunodeficiency virus (HIV)+ patients with squamous cell anal cancer (SCAC) may lead to de-escalation of treatment intensity. The objective of this study is to evaluate clinical outcomes including toxicity following standard concurrent curative-intent chemoradiation for HIV+ and HIV- patients with SCAC. MATERIALS AND METHODS: Among 97 evaluable patients treated between 2009 and 2016 (median age 52.2 y), 43 (44.3%) were HIV+ and 54 (55.7%) HIV-. The majority of the radiation was delivered using intensity-modulated radiation therapy and chemotherapy consisting primarily (93%) of 5-fluorouracil and mitomycin C. Clinical outcomes assessed included toxicity, locoregional control (LRC), distant metastasis (DM), progression-free survival (PFS), colostomy-free survival (CFS), overall survival (OS), and cause-specific survival (CSS). RESULTS: With a median follow-up of 45 months, HIV+ patients exhibited a trend toward reduced OS compared with HIV- patients (4 y OS 61.2% vs. 78.3%; HR 2.09; 95% CI, 0.97-4.52; P=0.055) on univariable analysis, but HIV status was not significant after adjusting for additional parameters on multivariable analysis. Toxicity rates, LRC, CFS, PFS, freedom from DM, and CSS were similar between the 2 cohorts. On multivariable analysis, tumor size >5 cm impacted all clinical outcomes (trend for LRC) except CFS. Radiation treatment extension beyond 7 days was found to negatively impact LRC and CSS. Male sex was associated with worse CFS. CONCLUSIONS: Radiation therapy with concurrent 5-fluorouracil and mitomycin C chemotherapy is reasonably well-tolerated as curative treatment for HIV+ patients with SCAC, and no significant difference in outcomes was noted relative to HIV- patients.

Patterns of proton therapy use in pediatric cancer management in 2016: An international survey.

PURPOSE: To facilitate the initiation of observational studies on late effects of proton therapy in pediatric patients, we report on current patterns of proton therapy use worldwide in patients aged less than 22 years. MATERIALS & METHODS: Fifty-four proton centers treating pediatric patients in 2016 in 11 countries were invited to respond to a survey about the number of patients treated during that year by age group, intent of treatment, delivery technique and tumor types. RESULTS: Among the 40 participating centers (participation rate: 74%), a total of 1,860 patients were treated in 2016 (North America: 1205, Europe: 432, Asia: 223). The numbers of patients per center ranged from 1 to 206 (median: 29). Twenty-four percent of the patients were <5 years of age, and 50% <10 years. More than 30 pediatric tumor types were identified, mainly treated with curative intent: 48% were CNS, 25% extra-cranial sarcomas, 7% neuroblastoma, and 5% hematopoietic tumors. About half of the patients were treated with pencil beam scanning. Treatment patterns were broadly similar across the three continents. CONCLUSION: To our knowledge, this survey provides the first worldwide assessment of proton therapy use for pediatric cancer management. Since previous estimates in the United States and Europe, CNS tumors remain the cancer types most commonly treated with protons in 2016. However, the proportion of extra-cranial tumors is growing worldwide. The typically low numbers of patients treated in each center indicate the need for international research collaborations to assess long-term outcomes of proton therapy in pediatric patients.

Long-term Outcome of Prostate Cancer Patients Who Exhibit Biochemical Failure Despite Salvage Radiation Therapy After Radical Prostatectomy.

OBJECTIVES: Salvage radiation therapy (SRT) is an effective treatment for recurrent prostate cancer (PCa) after radical prostatectomy. We report the long-term outcome of men who developed biochemical recurrence (BCR) after SRT and were treated >14 years ago. METHODS: In total, 61 patients treated with SRT from 1992 to 2000 at our institution were identified. Survival was calculated by Kaplan-Meier method. Log-rank test and Cox regression were used to determine significance of clinical parameters. RESULTS: The median follow-up was 126 months (interquartile range, 66-167 mo). Thirty-four (56%) had prostate-specific antigen (PSA) failure after SRT. At 10 years, overall survival (OS) was 67%, freedom from PSA failure (FFPF) was 33%, prostate cancer-specific survival (PCSS) was 84%, and distant metastases-free survival (DMFS) was 84%. Pathologic T-stage, Gleason score, seminal vesicle involvement, and pre-SRT PSA were associated with FFPF. For patients who failed SRT, the median time to BCR after SRT was 30 mo. A total of 19 (68%) received androgen deprivation therapy. The median OS was 13.6 years. At 10 years from time of BCR, OS was 59%, PCSS was 73%, DMFS was 75%, and castration-resistant-free survival was 70%. Early SRT failure correlated with significantly decreased DMFS and PCSS. Ten-year DMFS from SRT was 43% (BCR≤1 y) versus 91% (BCR>1 y). CONCLUSIONS: Extended follow-up demonstrates that despite SRT failure, PCSS remains high in select patients. Early failure (≤1 y after SRT) predicted for significantly worse outcome and may represent a subgroup with more aggressive disease that may be considered for further prospective clinical studies.

3BP2-deficient mice are osteoporotic with impaired osteoblast and osteoclast functions.

A fine balance between bone resorption by osteoclasts and bone formation by osteoblasts maintains bone homeostasis. In patients with cherubism, gain-of-function mutations in 3BP2, which is encoded by SH3-domain binding protein 2 (SH3BP2), cause cystic lesions with activated osteoclasts that lead to craniofacial abnormalities. However, little is known about the function of wild-type 3BP2 in regulating bone homeostasis. Here we have shown that 3BP2 is required for the normal function of both osteoblasts and osteoclasts. Initial analysis showed that Sh3bp2-/-mice developed osteoporosis as a result of reduced bone formation despite the fact that bone resorption was impaired. We demonstrated using reciprocal bone marrow chimeras, a cell-intrinsic defect of the osteoblast and osteoclast compartments in vivo. Further, Sh3bp2-/- osteoblasts failed to mature and form mineralized nodules in vitro, while Sh3bp2-/- osteoclasts spread poorly and were unable to effectively degrade dentine matrix in vitro. Finally, we showed that 3BP2 was required for Abl activation in osteoblasts and Src activation in osteoclasts, and demonstrated that the in vitro defect of each cell type was restored by the respective expression of activated forms of these kinases. These findings reveal an unanticipated role for the 3BP2 adapter protein in osteoblast function and in coordinating bone homeostatic signals in both osteoclast and osteoblast lineages.

Cherubism gene Sh3bp2 is important for optimal bone formation, osteoblast differentiation, and function.

INTRODUCTION: Cherubism is a human genetic disorder that causes bilateral symmetrical enlargement of the maxilla and the mandible in children. It is caused by mutations in SH3BP2. The exact pathogenesis of the disorder is an area of active research. Sh3bp2 knock-in mice were developed by introducing a Pro416Arg mutation (Pro418Arg in humans) in the mouse genome. The osteoclast phenotype of this mouse model was recently described. METHODS: We examined the bone phenotype of the cherubism mouse model, the role of Sh3bp2 during bone formation, osteoblast differentiation, and osteoblast function. RESULTS: We observed delays in early postnatal development of homozygous Sh3bp2(KI/KI) mice, which exhibited increased growth plate thickness and significantly decreased trabecular bone thickness and bone mineral density. Histomorphometric and microcomputed tomography analyses showed bone loss in the cranial and appendicular skeletons. Sh3bp2(KI/KI) mice also exhibited a significant decrease in osteoid formation that indicated a defect in osteoblast function. Calvarial osteoblast cell cultures had decreased alkaline phosphatase expression and mineralization, suggesting reduced differentiation potential. Gene expression of osteoblast differentiation markers such as collagen type I, alkaline phosphatase, and osteocalcin were decreased in osteoblast cultures from Sh3bp2(KI/KI) mice. CONCLUSIONS: These data suggest that Sh3bp2 regulates bone homeostasis through not only osteoclast-specific effects, but also through effects on osteoblast differentiation and function.

Pro416Arg cherubism mutation in Sh3bp2 knock-in mice affects osteoblasts and alters bone mineral and matrix properties.

Cherubism is an autosomal dominant disorder in children characterized by unwarranted symmetrical bone resorption of the jaws with fibrous tissue deposition. Mutations causing cherubism have been identified in the adaptor protein SH3BP2. Knock-in mice with a Pro416Arg mutation in Sh3bp2 exhibit a generalized osteoporotic bone phenotype. In this study, we examined the effects of this "cherubism" mutation on spectroscopic indices of "bone quality" and on osteoblast differentiation. Fourier-transform infrared imaging (FTIRI) analysis of femurs from wild-type and Sh3bp2 knock-in mice showed decreased mineral content, decreased mineral crystallinity/crystal size, and increased collagen maturity in homozygous mutants. To assess osteoblast maturation in vivo, knock-in mice were crossed with transgenic mice over-expressing GFP driven by 3.6-kb or 2.3-kb Col1a1 promoter fragments. Reduced numbers of mature osteoblasts were observed in homozygous mice. Neonatal calvarial cultures, which were enriched for osteoblasts by depletion of hematopoietic cells (negative selection for Ter119- and CD45-positive cells) were investigated for osteoblast-specific gene expression and differentiation, which demonstrated that differentiation and mineralization in homozygous osteoblast cultures was impaired. Co-cultures with calvarial osteoblasts and bone marrow macrophages showed that mutant osteoblasts appear to increase osteoclastogenesis resulting in increased bone resorption on bone chips. In summary, the Sh3bp2 mutation in cherubism mice alters bone quality, reduces osteoblast function, and may contribute to excessive bone resorption by osteoclasts. Our data, together with previous osteoclast studies, demonstrate a critical role of Sh3bp2 in bone remodeling and osteoblast differentiation.

Vitamin D and bone physiology: demonstration of vitamin D deficiency in an implant osseointegration rat model.

PURPOSE: The patient population varies in nutritional deficiencies, which may confound the host response to biomaterials. The objective of this study was to evaluate the effect of a common deficiency of vitamin D on implant osseointegration in the rat model. MATERIALS AND METHODS: Male Sprague-Dawley rats were maintained under the cessation of vitamin D intake and UV exposure. The serum levels of 1,25(OH)(2)D(3), 25 OHD(3), Ca, and P were determined. Miniature cylindrical Ti6Al4V implants (2-mm long, 1-mm diameter) were fabricated with double acid-etched (DAE) surface or modified DAE with discrete crystalline deposition (DCD) of hydroxyapatite nanoparticles. DAE and DCD implants were placed in the femurs of vitamin D-insufficient and control rats. After 14 days of healing, the femur-implant samples were subjected to implant push-in test and nondecalcified histology. The surfaces of recovered implant specimens after the push-in test were further evaluated by scanning electron microscopy (SEM). RESULTS: The decreased serum level of 25 OHD(3) demonstrated the establishment of vitamin D insufficiency in this model. The implant push-in test revealed that DAE and DCD implants in the vitamin D-insufficient group (15.94 +/- 8.20 N, n = 7; 15.63 +/- 3.96 N, n = 7, respectively) were significantly lower than those of the control group (24.99 +/- 7.92 N, n = 7, p < 0.05; 37.48 +/- 17.58 N, n = 7, p < 0.01, respectively). The transcortical bone-to-implant contact ratio (BIC) was also significantly decreased in the vitamin D-insufficient group. SEM analyses further suggested that the calcified tissues remaining next to the implant surface after push-in test appeared unusually fragmented. CONCLUSIONS: The effect of vitamin D insufficiency significantly impairing the establishment of Ti6Al4V implant osseointegration in vivo was unexpectedly profound. The outcome of Ti-based endosseous implants may be confounded by the increasing prevalence of vitamin D insufficiency in our patient population.

Introduction of a Phe377del mutation in ANK creates a mouse model for craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD) is a monogenic human disorder characterized by thickening of craniofacial bones and flaring metaphyses of long bones. Mutations for autosomal dominant CMD have been identified in the progressive ankylosis gene ANKH. Previous studies of Ank loss-of-function models, Ank(null/null) and Ank(ank/ank) mice, suggest that Ank plays a role in the regulation of bone mineralization. However, the mechanism for Ank mutations leading to CMD remains unknown. We generated the first knockin (KI) mouse model for CMD expressing a human mutation (Phe377 deletion) in ANK. Homozygous Ank knockin mice (Ank(KI/KI)) replicate many typical features of human CMD including hyperostosis of craniofacial bones, massive jawbones, decreased diameters of cranial foramina, obliteration of nasal sinuses, fusion of middle ear bones, and club-shaped femurs. In addition, Ank(KI/KI) mice have increased serum alkaline phosphatase and TRACP5b, as reported in CMD patients. Biochemical markers of bone formation and bone resorption, N-terminal propeptide of type I procollagen and type I collagen cross-linked C-terminal telopeptide, are significantly increased in Ank(KI/KI) mice, suggesting increased bone turnover. Interestingly, Ank(KI/KI) bone marrow-derived macrophage cultures show decreased osteoclastogenesis. Despite the hyperostotic phenotype, bone matrix in Ank(KI/KI) mice is hypomineralized and less mature, indicating that biomechanical properties of bones may be compromised by the Ank mutation. We believe this new mouse model will facilitate studies of skeletal abnormalities in CMD at cellular and molecular levels.

Thrombus organization and healing in the swine experimental aneurysm model. Part I. A histological and molecular analysis.

OBJECT: The authors describe the process of thrombus organization in the swine surgical aneurysm model. METHODS: Lateral carotid artery aneurysms with immediately induced thrombosis were created in 31 swine for a time-course study. Aneurysms were evaluated at 1, 3, 7, 14, 30, and 90 days after they were created. Histological analyses included quantitative immunohistochemical studies and evaluation of collagen deposition. Complementary DNA microarray analysis was performed for gene expression profiling. The lists of up- and downregulated genes were cross-matched with lists of genes known to be associated with cytokines or the extracellular matrix. The expression of selected genes was quantified using real-time polymerase chain reaction. Functional clustering was performed with the Expression Analysis Systematic Explorer (EASE) bioinformatics package. RESULTS: Histological analysis demonstrated leukocyte and macrophage infiltration in the thrombus at Day 3, myofibroblast infiltration at Days 7 to 14, and progressive collagen deposition and contraction thereafter. Tissue organization occurred in a centripetal fashion. A previously undescribed reticular network of connective tissue was observed at the periphery of the aneurysm at Day 3. Macrophages appeared critical to this thrombus organization. A total of 1109 genes were significantly changed from reference time zero during the time course: CXCL14, which produces a monocyte-specific chemokine, was upregulated over 100-fold throughout the time course; IGF1 was upregulated fourfold at Day 7, whereas IGFBP2 was downregulated approximately 50% at Days 7 and 14. Osteopontin (SPP1) upregulation increased from 30-fold at Day 30 to 45-fold at Day 14. The EASE analysis yielded eight functional classes of gene expression. CONCLUSIONS: This investigation provides a detailed histological and molecular analysis of thrombus organization in the swine aneurysm model. The companion study will describe the effect of embolic bioabsorbable polymers on this process.

Thrombus organization and healing in an experimental aneurysm model. Part II. The effect of various types of bioactive bioabsorbable polymeric coils.

OBJECT: Bioabsorbable polymeric material coils are being used in the endovascular treatment of aneurysms to achieve better thrombus organization than is possible using bare platinum coils. We used immunohistochemical and molecular biological analysis techniques in experimental aneurysms implanted with three different bioabsorbable polymer coils and platinum coils. METHODS: The degradation kinetics of nine polymer candidates for further analysis were first analyzed in vitro, and three materials with different degradation rates were selected. Seventy-four aneurysms were created in 37 swine using the venous pouch technique. The aneurysms were surgically implanted with one of the materials as follows (time points = 3, 7, and 14 days): Group 1, Guglielmi detachable coils (platinum); Group 2, Polysorb (90:10 polyglycolic acid [PGA]/polylactic acid); Group 3, Maxon (PGA/trimethylene carbonate); and Group 4, poly-l-lactic acid. Histological, immunohistochemical, and cDNA microarray analyses were performed on tissue specimens. RESULTS: Groups 1 and 4 showed minimal inflammatory response adjacent to the coil mass. In Group 2, Polysorb elicited a unique, firm granulation tissue that accelerated intraaneurysmal thrombus organization. In Group 3 intermediate inflammatory reactions were seen. Microarray analysis with Expression Analysis Sytematic Explorer software showed functional-cluster-gene activation to be increased at Day 7, preceding the histologic manifestation of polymer-induced granulation tissue at Day 14. A profile of expression changes in cytokine-related and extracellular membrane-related genes was compiled. CONCLUSIONS: Degradation speed was not the only factor determining the strength of the biological response. Polysorb induced an early, unique granulation tissue that conferred greater mechanical strength to the intraaneurysmal coilthrombus complex. Enhancing the formation of this polymer-induced granulation tissue may provide a new direction for improving long-term anatomical outcomes in cases involving aneurysms embolized with detachable coils.