Development Of Radiation-induced Fibrosis Research Articles

Thoracic Proton Minibeam Radiation Therapy: Tissue Preservation and Survival Advantage Over Conventional Proton Therapy

PurposeProton Minibeam Radiotherapy (pMBRT) is an innovative radiation therapy approach that highly modulates the spatial dimension of the dose delivery using narrow, parallel, and submillimetric proton beamlets. pMBRT has proven its remarkable healthy tissue preservation in the brain and skin. This study assesses the potential advantages of pMBRT for thoracic irradiations compared to conventional radiotherapy in terms of normal tissue toxicity. The challenge here was the influence of respiratory motion on the typical peak and valley dose patterns of pMBRT and its potential biological impact. Methods and materialsthe whole thorax of naïve C57BL/6 mice received one fraction of high dose (18 Gy) pMBRT or conventional proton therapy (CPT) without any respiratory control. The development of radiation-induced pulmonary fibrosis was longitudinally monitored using cone-beam computed tomography. Anatomopathological analysis was carried out at 9 months post-irradiation and focused on the reaction of the lungs’ parenchyma and the response of cell types involved in the development of radiation-induced fibrosis and lung regeneration as Alveolar Type II (AT2) epithelial cells, club cells, and macrophages. ResultspMBRT has milder effects on survival, skin reactions, and lung fibrosis compared to CPT. The pMBRT-induced lung changes were more regional and less severe, with evidence of potential reactive proliferation of AT2 epithelial cells and less extensive depletion of club cells and macrophage invasion than the more damaging effects observed in CPT. ConclusionpMBRT appears suitable to treat moving targets, holding a significant ability to preserve healthy lung tissue, even without respiratory control or precise targeting.

Radiomic analysis for early differentiation of lung cancer recurrence from fibrosis in patients treated with lung stereotactic ablative radiotherapy.

The development of radiation-induced fibrosis after SABR can obscure follow-up images and delay detection of a local recurrence in early-stage lung cancer patients. The objective of this study was to develop a radiomics model for computer-assisted detection of local recurrence and fibrosis for an earlier timepoint (<1 year) after the SABR treatment.&#xD;&#xD;This retrospective clinical study included CT images (n=107) of 66 patients treated with SABR. A z-score normalization technique was used for radiomic feature standardization across scanner protocols. The training set for the radiomics model consisted of CT images (66 patients; 22 recurrences and 44 fibrosis) obtained at 24 months (median) follow-up. The test set included CT-images of 41 patients acquired at 5-12 months follow-up. Combinations of four widely used machine learning techniques (support vector machines (SVMs), gradient boosting, random forests (RF), and logistic regression (LR)) and feature selection methods (Relief feature scoring, maximum relevance minimum redundancy (MRMR), mutual information maximization (MIM), forward feature selection, and LASSO) were investigated. Pyradiomics was used to extract 106 radiomic features from the CT-images for feature selection and classification. &#xD;&#xD;An RF + LASSO model scored the highest in terms of AUC (0.87) and obtained a sensitivity of 75% and a specificity of 88% in identifying a local recurrence in the test set. In the training set, 86% accuracy was achieved using five-fold cross-validation. Delong's test indicated that AUC achieved by the RF+LASSO is significantly better than 11 other machine learning models presented here. The top three radiomic features: Interquartile Range (first order), Cluster Prominence (GLCM), and Autocorrelation (GLCM), were revealed as differentiating a recurrence from fibrosis with this model.&#xD;&#xD;The radiomics model selected, out of multiple machine learning and feature selection algorithms, was able to differentiate a recurrence from fibrosis in earlier follow-up CT-images with a high specificity rate and satisfactory sensitivity performance. &#xD.

Dosimetric Quantities in Neuroendocrine Tumors over Treatment Cycles with 177Lu-DOTATATE.

Tumor dosimetry was performed for 177Lu-DOTATATE with the aims of better understanding the range and variation of the tumor-absorbed doses (ADs), how different dosimetric quantities evolve over the treatment cycles, and whether this evolution differs depending on the tumor grade. Such information is important for radiobiologic interpretation and may inform the design of alternative administration schemes. Methods: The data came from 41 patients with neuroendocrine tumors (NETs) of grade 1 (n = 23) or 2 (n = 18) who had received between 2 and 9 treatment cycles. Dosimetry was performed for 182 individual lesions, giving a total of 880 individual AD assessments across all cycles. Hybrid planar-SPECT/CT imaging was used, including quantitative SPECT reconstruction, voxel-based absorbed-dose-rate calculation, semiautomatic image segmentation, and partial-volume correction. Linear mixed-effect models were used to analyze changes in tumor ADs over cycles, absorbed-dose rates and activity concentrations on day 1, effective half-times, and tumor volumes. Tumors smaller than 8 cm3 were excluded from analyses. Results: Tumor ADs ranged between 2 and 77 Gy per cycle. On average, the AD decreased over the cycles, with significantly different rates (P < 0.05) of 6% and 14% per cycle for grade 1 and 2 NETs, respectively. The absorbed-dose rates and activity concentrations on day 1 decreased by similar amounts. The effective half-times were less variable but shorter for grade 2 than for grade 1 (P < 0.001). For grade 2 NETs, the tumor volumes decreased, with a similar tendency in grade 1. Conclusion: The tumor AD, absorbed-dose rate, and activity uptake decrease, in parallel with tumor volumes, between 177Lu-DOTATATE treatment cycles, particularly for grade 2 NETs. The effective half-times vary less but are lower for grade 2 than grade 1 NETs. These results may indicate the development of radiation-induced fibrosis and could have implications for the design of future treatment and dosimetry protocols.

Common European Mitochondrial Haplogroups in the Risk for Radiation-induced Subcutaneous Fibrosis in Breast Cancer Patients

AimsThe contribution of mitochondrial DNA (mtDNA) variations to clinical radiosensitivity is largely unknown. In the present study, we evaluated the association between mtDNA haplogroups and the risk of radiation-induced subcutaneous fibrosis after postoperative radiotherapy in breast cancer patients. Materials and methodsSubcutaneous fibrosis was scored according to the Late Effects of Normal Tissue-Subjective Objective Management Analytical (LENT-SOMA) scale in 286 Italian breast cancer patients who received radiotherapy after breast-conserving surgery. Eight mtDNA single nucleotide polymorphisms that define the nine major haplogroups in the European population were determined by polymerase chain reaction restriction fragment length polymorphism analysis on genomic DNA extracted from peripheral blood. ResultsIn a Kaplan–Meier analysis evaluated by the Log-rank test, carriers of haplogroup H were found to be at lower risk of grade ≥2 subcutaneous fibrosis (P = 0.018) compared with all other haplotypes combined. In the multivariate Cox regression analysis adjusted for clinical factors (body mass index, breast diameter, adjuvant treatment, dose per fraction, radiation type and acute skin toxicity), haplogroup H emerged as a protective factor for moderate to severe radiation-induced fibrosis at a nominal significance level (hazard ratio: 0.50, 95% confidence interval 0.27–0.92, P = 0.027), which did not survive correction for multiple testing. ConclusionsOur results suggest a protective effect of the mitochondrial haplogroup H in the development of radiation-induced fibrosis in breast cancer patients. However, the loss of statistical significance after correction for multiple comparisons and the lack of an independent validation cohort make our findings preliminary, requiring further confirmation in large-scale prospective studies.

Association of XRCC1 and XRCC3 gene haplotypes with the development of radiation-induced fibrosis in patients with nasopharyngeal carcinoma.

Radiation-induced fibrosis is one of the late complications of radiotherapy (RT) for nasopharyngeal carcinoma (NPC). The aim of this study was to investigate the association between X-ray repair cross-complementing protein 1 and 3 (XRCC1 and XRCC3, respectively) gene haplotypes and radiation-induced fibrosis in NPC patients. Genomic DNA was extracted from blood samples of 120 NPC patients previously treated with RT. In total, 12 tag single-nucleotide polymorphisms (SNPs) were selected from the XRCC1 and XRCC3 genes and were genotyped using restriction fragment length polymorphism analysis or unlabeled probe melting analysis. Single-marker and haplotype analyses were performed using multivariate logistic regression analysis. The functional variant rs861539 of XRCC3 may be associated with radiation-induced fibrosis [asymptotic P-value (Pasym)<0.05]. No significant association was observed between radiation-induced fibrosis and any of the tag SNPs of XRCC1 and XRCC3 in either single-marker or haplotype analysis after 10,000 permutations [empirical P-value (Pemp)>0.05]. Our preliminary results indicated that the rs861539 variant of XRCC3 may be associated with an increased risk of radiation-induced fibrosis; however, a large-scale study is required to confirm this result.

Mesenchymal stem cells transplants after pelvic radiotherapy limits the development of radiation-induced fibrosis, without promoting the residual tumor growth

Mesenchymal stem cells transplants after pelvic radiotherapy limits the development of radiation-induced fibrosis, without promoting the residual tumor growth

Inhibition of radiation-induced skin fibrosis with imatinib

Purpose: Dermal fibrosis is a disabling late toxicity of radiotherapy. Several lines of evidence suggest that overactive signaling via the Platelet-derived growth factor receptor-beta (PDGFR-β) and V-abl Abelson murine leukemia viral oncogene homolog 1 (cAbl) may be etiologic factors in the development of radiation-induced fibrosis. We tested the hypothesis that imatinib, a clinically available inhibitor of PDGFR-β, Mast/stem cell growth factor receptor (c-kit) and cAbl, would reduce the severity of dermal fibrosis in a murine model.Materials and methods: The right hind legs of female C3H/HeN mice were exposed to 35 Gy of X-rays. Cohorts of mice were maintained on chow formulated with imatinib 0.5 mg/g or control chow for the duration of the experiment. Bilateral hind limb extension was measured serially to assess fibrotic contracture. Immunohistochemistry and biochemical assays were used to evaluate the levels of collagen and cytokines implicated in radiation-induced fibrosis.Results: Imatinib treatment significantly reduced hind limb contracture and dermal thickness after irradiation. Immunohistochemical studies demonstrated a substantial reduction in PDGFR-β phosphorylation. We also observed reduced Transforming Growth factor-β (TGF-β) and collagen expression in irradiated skin of imatinib-treated mice, suggesting that imatinib may suppress the fibrotic process by interrupting cross-talk between these pathways.Conclusions: Taken together, these results support that imatinib may be a useful agent in the prevention and treatment of radiation-induced dermal fibrosis.

INFLAMMATORY CELL RECRUITMENT FOLLOWING THORACIC IRRADIATION

Ionizing radiation leads to a progressive injury in which a monocyte/macrophage-rich pneumonitis is followed by a chronic progressive fibrosis. In the present study, the role of macrophage/monocyte recruitment in the genesis of radiation-induced pulmonary fibrosis was examined. The objectives were threefold: (i) characterize the inflammatory cells recruited into the lung during the development of radiation-induced fibrosis; (ii) investigate changes in lung response following depletion of resident alveolar macrophages in vivo prior to radiation treatment; (iii) assess if inhalation of low levels of endotoxin would potentiate the radiation-initiated injury. One group of fibrosis-sensitive C57BL/6 mice was irradiated with a single dose of 15 Gy to the thorax. In a second group, resident inflammatory cells were depleted using clodronate, encapsulated into liposomes, 48 hours prior to irradiation with a single dose of 15 Gy to the thorax. Control animals were sham irradiated. All groups of animals then were examined 8, 16, or 24 weeks post irradiation. No difference in total cell numbers or cell differentials was observed between irradiated mice or those that were both liposome treated and irradiated at any time point. At 16 weeks, mice that received radiation showed a 5- to 6-fold increase in lymphocytes regardless of treatment as compared to control animals. At 24 weeks post irradiation, select groups were exposed to lipopolysaccharide (LPS) and examined 24 hours post inhalation. Lavageable protein was increased several fold in mice that received both radiation and LPS exposure as compared to 15 Gy or LPS exposure alone. These results demonstrate: (i) macrophages and lymphocytes are the predominately recruited cell types through 24 weeks post irradiation; (ii) recovery of inflammatory cells, regardless of prior macrophage depletion, were similar, suggesting that early responses are primarily driven by parenchymal cell injury; (iii) thoracic irradiation-induced injury can cause sensitization to a secondary stimulus that may result in injuries/responses not predicted by evaluating exposures individually.

Prevention of radiation-induced nephropathy and fibrosis in a model of bone marrow transplant by an angiotensin II receptor blocker.

Nephropathy, interstitial pneumopathy, and renal and lung fibrosis are major complications of bone marrow transplantation (BMT). This study evaluated the antifibrotic property of an angiotensin II (A2) type-1 receptor blocker (L-159,809) and compared it with those of Captopril and Enalapril, two angiotensin-converting enzyme (ACE) inhibitors, in a rat model of BMT. Male WAG/Rij/MCW rats received a preparative regimen of 60 mg/kg body wt of cytoxan (i.p., Days 9 and 8) and 18.5 Gy of total body irradiation (TBI) in six twice daily fractions (Days 2, 1, and 0) followed immediately (Day 0) by BMT. Modifiers were given in drinking water from Day 10 until autopsy, 8 weeks after BMT. Rats treated with TBI plus cytoxan alone developed severe nephropathy. Trichrome staining showed marked collagen deposition in glomeruli, renal interstitium, and renal arteries and arterioles (especially in their adventitia). Collagen deposition and renal damage were markedly reduced by the three modifiers. Of the three, L-158,809-treated rats had slightly thinner vessels and slightly less collagen than nonirradiated normal controls. The study shows the effectiveness of these drugs in the protection of the renal parenchyma from the development of radiation-induced fibrosis. It also indicates a role for angiotensin II in the modulation of collagen synthesis.

TGF-beta1-mediated alterations of rat lung fibroblast differentiation resulting in the radiation-induced fibrotic phenotype

Purpose : To study the influence of TGF-beta1 and TGF-beta-neutralizing antibodies on the clonogenic activity and terminal differentiation of rat lung fibroblasts following radiation exposure. Material and methods : Early passage rat lung fibroblasts were used in this study. Colony formation assays were applied to determine the radiation sensitivity as well as radiation-induced alterations in differentiation pattern. Based on a TGF-beta1-specific ELISA system, the amount of TGF-beta1 in the culture medium of sham-irradiated and irradiated cultures was determined. Results : Applying immediate (ip) and delayed plating (dp) procedures for cells irradiated in the subconfluent state, distinct differences in the radiation dose–response curves could be observed (SF2 ip 0.20 +/- 0.025 versus SF2 dp 0.51 +/- 0.0077). Upon irradiation with a single dose of 4 Gy the level of TGF-beta1 found in the culture medium increased by about 60%. Radiation-induced terminal differentiation of progenitor fibroblasts (MF) to postmitotic fibrocytes (PMF) was expressed by the change of the ratio of PMF:MF (0.8 at 0 Gy versus 3.0 at 4 Gy). Neutralizing antibodies directed against TGF-beta inhibited both the radiation-induced reduction in clonogenic activity of rat lung fibroblasts as well as the radiation-induced terminal differentiation of MF progenitor fibroblasts to PMF postmitotic fibrocytes. Conclusion : The results indicate the important role of TGF-beta1 in triggering radiation-induced inhibition of clonogenic activity as well as terminal differentiation of rat lung fibroblasts. The data presented support the hypothesis that terminal differentiation is an essential cellular process in the development of radiation-induced fibrosis in the lung.

Differentiation state of skin fibroblast cultures versus risk of subcutaneous fibrosis after radiotherapy

Background and purpose: There is increasing evidence for patient-to-patient variation in the response of normal tissue to radiotherapy. Recently, it has been suggested that accumulation of functional fibrocytes may be a key step in the development of radiation-induced fibrosis. Therefore, we have examined a possible relationship between the differentiation state of untreated fibroblasts and the risk of radiation-induced subcutaneous fibrosis in individual patients. Materials and methods: We used skin fibroblast cultures isolated from eight postmastectomy radiotherapy patients whose individual clinical radiosensitivity was assessed by the mean excess risk of fibrosis. Different types of potentially mitotic progenitor fibroblasts (MF) and postmitotic functional fibrocytes (PMF) in the terminal differentiation lineage, MFI→MFII→MFIII→PMF, were scored morphologically in clonal culture. Progression of differentiation was quantified by the ratio L/E of colony-forming late (MFIII and late MFII) and early (MFI and early MFII) progenitors. Results: We observed a correlation between the ratio L/E and the mean risk of fibrosis ( r S=0.743, P=0.03), indicating an approximately 10-fold increase in L/E with an increasing risk of fibrosis. This was paralleled by a decreasing trend in the absolute numbers of early progenitor types. By contrast, there was no significant correlation between the plating efficiency and the risk of fibrosis. Conclusions: The data suggest that the risk of fibrosis increases with the progression of the differentiation of untreated progenitor fibroblasts, indicating that the progression of fibroblast differentiation may be a co-factor in the development of radiation-induced fibrosis. If this hypothesis is validated, it provides a rationale for a novel predictive test to identify patients with an increased risk of subcutaneous fibrosis.