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Radiation and Environmental Biophysics Aug 2013Ionizing radiation is a well-known but little understood risk factor for lens opacities. Until recently, cataract development was considered to be a deterministic effect... (Review)
Review
Ionizing radiation is a well-known but little understood risk factor for lens opacities. Until recently, cataract development was considered to be a deterministic effect occurring at lens doses exceeding a threshold of 5-8 Gy. Substantial uncertainty about the level and the existence of a threshold subsists. The International Commission on Radiation Protection recently revised it to 0.5 Gy. Based on a systematic literature review of epidemiological studies on exposure to low levels of ionizing radiation and the occurrence of lens opacities, a list of criteria for new epidemiological studies was compiled, and a list of potential study populations was reviewed. Among 24 publications finally identified, six report analyses of acute exposures in atomic bomb survivors and Chernobyl liquidators, and the others report analyses of protracted exposures in occupationally, medically or accidentally exposed populations. Three studies investigated a dose threshold: in atomic bomb survivors, the best estimates were 1 Sv (95 % CI <0-0.8 Sv) regarding lensectomies; in survivors exposed as children, 0.6 Sv (90 % CI <0.0-1.2 Sv) for cortical cataract prevalence and 0.7 Sv (90 % CI 0.0-2.8 Sv) for posterior subcapsular cataract; and in Chernobyl liquidators, 0.34 Sv (95 % CI 0.19-0.68 Sv) for stage 1 cataract. Current studies are heterogeneous and inconclusive regarding the dose-response relationship. Protracted exposures and high lens doses occur in several occupational groups, for instance, in physicians performing fluoroscopy-guided interventional procedures, and in accidentally exposed populations. New studies with a good retrospective exposure assessment are feasible and should be initiated.
Topics: Cataract; Humans; Occupational Exposure; Radiation Dosage; Radiation Injuries; Radiation, Ionizing
PubMed: 23807741
DOI: 10.1007/s00411-013-0477-6 -
International Journal of Radiation... Nov 2017A systematic review and meta-analysis were conducted to evaluate the therapeutic outcomes of conventional radiation therapy (CRT) and hypofractionated radiation therapy... (Meta-Analysis)
Meta-Analysis Review
Conventional Versus Hypofractionated Radiation Therapy for Localized or Locally Advanced Prostate Cancer: A Systematic Review and Meta-analysis along with Therapeutic Implications.
PURPOSE
A systematic review and meta-analysis were conducted to evaluate the therapeutic outcomes of conventional radiation therapy (CRT) and hypofractionated radiation therapy (HRT) for localized or locally advanced prostate cancer (LLPCa).
METHODS AND MATERIALS
A total of 599 abstracts were extracted from 5 databases and screened in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Only phase III trials randomized between CRT and HRT in LLPCa with a minimum of 5 years of follow-up data were considered. The evaluated endpoints were biochemical failure, biochemical and/or clinical failure, overall mortality, prostate cancer-specific mortality, and both acute and late gastrointestinal (GI) and genitourinary (GU) (grade ≥2) toxicity.
RESULTS
Ten trials from 9 studies, with a total of 8146 patients (CRT, 3520; HRT, 4626; 1 study compared 2 HRT schedules with a common CRT regimen), were included in the evaluation. No significant differences were found in the patient characteristics between the 2 arms. However, the RT parameters differed significantly between CRT and HRT (P<.001 for all). The use of androgen deprivation therapy varied from 0% to 100% in both groups (mean ± standard deviation 43.3% ± 43.6% for CRT vs HRT; P=NS). The odds ratio, risk ratio, and risk difference (RD) between CRT and HRT for biochemical failure, biochemical and/or clinical failure, overall mortality, prostate cancer-specific mortality, acute GU toxicity, and late GU and GI toxicities were all nonsignificant. Nevertheless, the incidence of acute GI toxicity was 9.1% less with CRT (RD 0.091; odds ratio 1.687; risk ratio 1.470; P<.001 for all). On subgroup analysis, the patient groups with ≤66.8% versus >66.8% androgen deprivation therapy (RD 0.052 vs 0.136; P=.008) and <76% versus ≥76% full seminal vesicles in the clinical target volume (RD 0.034 vs 0.108; P<.001) were found to significantly influence the incidence of acute GI toxicity with HRT.
CONCLUSIONS
HRT provides similar therapeutic outcomes to CRT in LLPCa, except for a significantly greater risk of acute GI toxicity. HRT enables a reduction in the overall treatment time and offers patient convenience. However, the variables contributing to an increased risk of acute GI toxicity require careful consideration.
Topics: Clinical Trials, Phase III as Topic; Humans; Male; Prostatic Neoplasms; Radiation Dose Hypofractionation; Radiotherapy; Randomized Controlled Trials as Topic; Relative Biological Effectiveness
PubMed: 29280452
DOI: 10.1016/j.ijrobp.2017.07.021 -
Current Oncology (Toronto, Ont.) May 2022Selective internal radiation therapy (SIRT) with yttrium-90 (Y)-loaded microspheres is increasingly used for the treatment of Intrahepatic Cholangiocarcinoma (ICC).... (Review)
Review
Selective internal radiation therapy (SIRT) with yttrium-90 (Y)-loaded microspheres is increasingly used for the treatment of Intrahepatic Cholangiocarcinoma (ICC). Dosimetry verifications post-treatment are required for a valid assessment of any dose-response relationship. We performed a systematic review of the literature to determine how often clinics conducted post-treatment dosimetry verification to measure the actual radiation doses delivered to the tumor and to the normal liver in patients who underwent SIRT for ICC, and also to explore the corresponding dose-response relationship. We also investigated other factors that potentially affect treatment outcomes, including the type of microspheres used and concomitant chemotherapy. Out of the final 47 studies that entered our study, only four papers included post-treatment dosimetry studies after SIRT to quantitatively assess the radiation doses delivered. No study showed that one microsphere type provided a benefit over another, one study demonstrated better imaging-based response rates associated with the use of glass-based TheraSpheres, and two studies found similar toxicity profiles for different types of microspheres. Gemcitabine and cisplatin were the most common chemotherapeutic drugs for concomitant administration with SIRT. Future studies of SIRT for ICC should include dosimetry to optimize treatment planning and post-treatment radiation dosage measurements in order to reliably predict patient responses and liver toxicity.
Topics: Humans; Bile Duct Neoplasms; Bile Ducts, Intrahepatic; Chemoradiotherapy; Cholangiocarcinoma; Yttrium Radioisotopes
PubMed: 35735415
DOI: 10.3390/curroncol29060306 -
International Journal of Radiation... Oct 2021Limited evidence is available on the utility of dose-escalated radiation therapy (DE-RT) with or without temozolomide (TMZ) versus standard-of-care radiation therapy... (Meta-Analysis)
Meta-Analysis
PURPOSE
Limited evidence is available on the utility of dose-escalated radiation therapy (DE-RT) with or without temozolomide (TMZ) versus standard-of-care radiation therapy (SoC-RT) for patients with newly diagnosed glioblastoma multiforme. We performed a systematic review/meta-analysis to compare overall survival (OS) and progression-free survival (PFS) between DE-RT and SoC-RT.
METHODS AND MATERIALS
We used a Population, Intervention, Control, Outcomes, Study Design/Preferred Reporting Items for Systematic Reviews and Meta-analyses/Meta-analysis of Observational Studies in Epidemiology selection criterion to identify studies. The primary and secondary outcomes were 1-year OS and 1-year PFS, respectively. Outcomes and comparisons were subdivided based on receipt of TMZ and MGMT status. DE-RT was defined based on equivalent dose calculations. Random effects meta-analyses using the Knapp-Hartung correction, arcsine transformation, and restricted maximum likelihood method were conducted. Meta-regression was used to compare therapeutic (eg, DE-RT or TMZ) and pathologic characteristics (eg, MGMT methylation status) using the Wald-type test.
RESULTS
Across 22 published studies, 2198 patients with glioblastoma multiforme were included; 507 received DE-RT. One-year OS after DE-RT alone was higher than SoC-RT alone (46.3% vs 23.4%; P = .02) as was 1-year PFS (17.9% vs 5.3%; P = .02). No significant difference in 1-year OS (73.2% vs 64.4%; P = .23) or 1-year PFS (44.5% vs 44.3%; P = .33) between DE-RT + TMZ and SoC-RT + TMZ was noted. No difference in 1-year OS was noted between DE-RT + TMZ and SoC-RT + TMZ in either MGMT methylated (83.2% vs 73.2%; P = .23) or MGMT unmethylated (72.6% vs 50.6%; P = .16) patients.
CONCLUSIONS
DE-RT alone resulted in superior PFS and OS versus SoC-RT alone. DE-RT + TMZ did not lead to improved outcomes versus SoC-RT + TMZ. No differential benefit based on MGMT status was found. Future studies are warranted to define which subgroups benefit most from DE-RT.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Brain Neoplasms; Child; DNA Modification Methylases; DNA Repair Enzymes; Glioblastoma; Humans; Middle Aged; Prospective Studies; Radiotherapy Dosage; Standard of Care; Temozolomide; Tumor Suppressor Proteins; Young Adult
PubMed: 33991621
DOI: 10.1016/j.ijrobp.2021.05.001 -
International Journal of Radiation... May 2021Dose escalation improves localized prostate cancer disease control, and moderately hypofractionated external beam radiation is noninferior to conventional fractionation....
PURPOSE
Dose escalation improves localized prostate cancer disease control, and moderately hypofractionated external beam radiation is noninferior to conventional fractionation. The evolving treatment approach of ultrahypofractionation with stereotactic body radiation therapy (SBRT) allows possible further biological dose escalation (biologically equivalent dose [BED]) and shortened treatment time.
METHODS AND MATERIALS
The American Association of Physicists in Medicine Working Group on Biological Effects of Hypofractionated Radiation Therapy/SBRT included a subgroup to study the prostate tumor control probability (TCP) with SBRT. We performed a systematic review of the available literature and created a dose-response TCP model for the endpoint of freedom from biochemical relapse. Results were stratified by prostate cancer risk group.
RESULTS
Twenty-five published cohorts were identified for inclusion, with a total of 4821 patients (2235 with low-risk, 1894 with intermediate-risk, and 446 with high-risk disease, when reported) treated with a variety of dose/fractionation schemes, permitting dose-response modeling. Five studies had a median follow-up of more than 5 years. Dosing regimens ranged from 32 to 50 Gy in 4 to 5 fractions, with total BED (α/β = 1.5 Gy) between 183.1 and 383.3 Gy. At 5 years, we found that in patients with low-intermediate risk disease, an equivalent doses of 2 Gy per fraction (EQD2) of 71 Gy (31.7 Gy in 5 fractions) achieved a TCP of 90% and an EQD2 of 90 Gy (36.1 Gy in 5 fractions) achieved a TCP of 95%. In patients with high-risk disease, an EQD2 of 97 Gy (37.6 Gy in 5 fractions) can achieve a TCP of 90% and an EQD2 of 102 Gy (38.7 Gy in 5 fractions) can achieve a TCP of 95%.
CONCLUSIONS
We found significant variation in the published literature on target delineation, margins used, dose/fractionation, and treatment schedule. Despite this variation, TCP was excellent. Most prescription doses range from 35 to 40 Gy, delivered in 4 to 5 fractions. The literature did not provide detailed dose-volume data, and our dosimetric analysis was constrained to prescription doses. There are many areas in need of continued research as SBRT continues to evolve as a treatment modality for prostate cancer, including the durability of local control with longer follow-up across risk groups, the efficacy and safety of SBRT as a boost to intensity modulated radiation therapy (IMRT), and the impact of incorporating novel imaging techniques into treatment planning.
Topics: Dose-Response Relationship, Radiation; Humans; Linear Models; Male; Models, Biological; Models, Theoretical; Probability; Prostatic Neoplasms; Radiation Dose Hypofractionation; Radiosurgery; Relative Biological Effectiveness; Risk; Time Factors; Treatment Outcome; Urethra
PubMed: 32900561
DOI: 10.1016/j.ijrobp.2020.08.014 -
Health Physics Nov 2020A systematic review of relevant studies that determined the dose response relationship (DRR) for the hematopoietic (H) acute radiation syndrome (ARS) in the canine...
A systematic review of relevant studies that determined the dose response relationship (DRR) for the hematopoietic (H) acute radiation syndrome (ARS) in the canine relative to radiation quality of mixed neutron:gamma radiations, dose rate, and exposure uniformity relative to selected reference radiation exposure has not been performed. The datasets for rhesus macaques exposure to mixed neutron:gamma radiation are used herein as a species comparative reference to the canine database. The selection of data cohorts was made from the following sources: Ovid Medline (1957-present), PubMed (1954-present), AGRICOLA (1976-present), Web of Science (1954-present), and US HHS RePORT (2002-present). The total number of hits across all search sites was 3,077. Several referenced, unpublished, non-peer reviewed government reports were unavailable for review. Primary published studies using canines, beagles, and mongrels were evaluated to provide an informative and consistent review of mixed neutron:gamma radiation effects to establish the DRRs for the H-ARS. Secondary and tertiary studies provided additional information on the hematologic response or the effects on hematopoietic progenitor cells, radiation dosimetry, absorbed dose, and organ dose. The LD50/30 values varied with neutron quality, exposure aspect, and mixed neutron:gamma ratio. The reference radiation quality varied from 250 kVp or 1-2 MeV x radiation and Co gamma radiation. A summary of a published review of a data set describing the DRR in rhesus macaques for mixed neutron:gamma radiation exposure in the H-ARS is included for a comparative reference to the canine dataset. The available evidence provided a reliable and extensive database that characterized the DRR for the H-ARS in canines and young rhesus macaques exposed to mixed neutron:gamma radiations of variable energy relative to 250 kVp, 1-2 MeV x radiation and Co gamma, and uniform and non-uniform total-body irradiation without the benefit of medical management. The mixed neutron:gamma radiation showed an energy-dependent RBE of ~ 1.0 to 2.0 relative to reference radiation exposure within both species. A marginal database described the DRR for the gastrointestinal (GI)-ARS. Medical management showed benefit in both species relative to the mixed neutron:gamma as well as exposure to reference radiation. The DRR for the H-ARS was characterized by steep slopes and relative LD50/30 values that reflected the radiation quality, exposure aspect, and dose rate over a range in time from 1956-2012.
Topics: Acute Radiation Syndrome; Animals; Dogs; Dose-Response Relationship, Radiation; Gamma Rays; Hematopoietic Stem Cells; Neutrons; Primates; Radiation Exposure; Reference Standards
PubMed: 32947486
DOI: 10.1097/HP.0000000000001319 -
International Journal of Radiation... Oct 2021Neoadjuvant concurrent chemoradiation therapy (nCRT) plus surgery has been a standard treatment for locoregionally advanced esophageal cancer and carcinoma of the... (Comparative Study)
Comparative Study
Comparison of Clinical Efficacy of Neoadjuvant Chemoradiation Therapy Between Lower and Higher Radiation Doses for Carcinoma of the Esophagus and Gastroesophageal Junction: A Systematic Review.
PURPOSE
Neoadjuvant concurrent chemoradiation therapy (nCRT) plus surgery has been a standard treatment for locoregionally advanced esophageal cancer and carcinoma of the gastroesophageal junction (EC/GEJ), but the optimal preoperative radiation dose is still unclear. We performed this systematic review to explore the treatment efficacy and toxicity of different radiation dose levels and find an optimal dose-fractionation strategy in EC/GEJ patients receiving nCRT.
METHODS AND MATERIALS
Embase and Ovid Medline were searched for articles involving cases of operable squamous and adenocarcinoma of the esophagus and GEJ in which patients received nCRT up to a dose of 50.4 Gy in 28 fractions that were published until July 2019, when the search was performed. Physical dose distributions were converted to biologically equivalent doses (BEDs), which were described in units of gray (alpha/beta). Pooled rates of overall survival (OS), progression-free survival (PFS), failure patterns, and toxicities were compared between lower-dose radiation therapy (LDRT; BED ≤48.85 Gy) and higher-dose radiation therapy (HDRT; BED >48.85 Gy) for patients treated with nCRT.
RESULTS
A total of 110 studies with 7577 EC/GEJ patients receiving nCRT were included in this pooled analysis. Both the PFS and OS rates of patients receiving LDRT were significantly higher than those of patients receiving HDRT. Patients receiving LDRT had improved safety regarding treatment-related adverse events and lower distant failure rates than patients receiving HDRT. Utilization of modern radiation therapy (RT) techniques, including 3-dimensional conformal RT and intensity modulated RT, was associated with improved oncologic outcomes compared with 2-dimensional methods. Subgroup analysis showed that EC/GEJ patients receiving conventionally fractionated radiation to a dose of 40.0 to 41.4 Gy in 20-23 fractions showed improved OS compared with those receiving radiation above this dose.
CONCLUSIONS
Based on the limited data, nCRT using BED ≤48.85 Gy was suitable for locoregionally advanced, resectable EC/GEJ. A total dose of 40.0 to 41.4 Gy in 20 to 23 fractions using modern RT techniques might provide the optimal therapeutic ratio.
Topics: Chemoradiotherapy; Esophageal Neoplasms; Esophageal Squamous Cell Carcinoma; Esophagogastric Junction; Humans; Neoadjuvant Therapy; Radiotherapy Dosage; Treatment Failure; Treatment Outcome
PubMed: 33964352
DOI: 10.1016/j.ijrobp.2021.04.031 -
Radiation Research Jan 2008Little, M. P., Tawn, E. J., Tzoulaki, I., Wakeford, R., Hildebrandt, G., Paris, F., Tapio, S. and Elliott, P. A Systematic Review of Epidemiological Associations Between... (Review)
Review
Little, M. P., Tawn, E. J., Tzoulaki, I., Wakeford, R., Hildebrandt, G., Paris, F., Tapio, S. and Elliott, P. A Systematic Review of Epidemiological Associations Between Low and Moderate Doses of Ionizing Radiation and Late Cardiovascular Effects, and Their Possible Mechanisms. Radiat. Res. 169, 99-109 (2008). The link between high doses of ionizing radiation and damage to the heart and coronary arteries is established. In this paper, we systematically review the epidemiological evidence for associations between low and moderate doses (<5 Gy) of ionizing radiation and late-occurring cardiovascular disease. Risks per unit dose in epidemiological studies vary over at least two orders of magnitude, possibly a result of confounding factors. An examination of possible biological mechanisms indicates that the most likely causative effect of radiation exposure is damage to endothelial cells and subsequent induction of an inflammatory response, although it seems unlikely that this would extend to low-dose and low-dose-rate exposure. However, a role for somatic mutation has been proposed that would indicate a stochastic effect. In the absence of a convincing mechanistic explanation of epidemiological evidence that is less than persuasive at present, a cause-and-effect interpretation of the reported statistical associations cannot be reliably inferred, although neither can it be reliably excluded. Further epidemiological and biological evidence will allow a firmer conclusion to be drawn.
Topics: Animals; Cardiovascular Diseases; Cardiovascular System; Dose-Response Relationship, Radiation; Environmental Exposure; Humans; Nuclear Weapons; Radiation, Ionizing
PubMed: 18159955
DOI: 10.1667/RR1070.1 -
La Radiologia Medica Oct 2018Radiation-induced health risks are broadly questioned in the literature. As cone beam computed tomography (CBCT) is increasingly used in non-dental examinations, its... (Review)
Review
BACKGROUND
Radiation-induced health risks are broadly questioned in the literature. As cone beam computed tomography (CBCT) is increasingly used in non-dental examinations, its effective dose needs to be known. This study aimed to review the published evidence on effective dose of non-dental CBCT for diagnostic use by focusing on dosimetry system used to estimate dose.
MATERIALS AND METHODS
A systematic review of the literature was performed on 12 November 2017. All the literature up to this date was included. The PubMed and web of science databases were searched. Studies were screened for inclusion based on defined inclusion and exclusion criteria according to the preferred reporting items for systematic reviews.
RESULTS
Fifteen studies met the inclusion criteria and were included in our review. Thirteen and two of them examined one and two anatomical areas, respectively. The anatomical areas were: ear (6), paranasal sinuses (4), ankle (3), wrist (2), knee (1), and cervical spine (1). Effective dose was estimated by different methods: (i) RANDO phantom associated with thermoluminescent dosimeters (6), metal oxide semiconductor field-effect transistor dosimeters (3), and optically stimulated luminescent dosimeters (1). (ii) Scanner outputs, namely computed tomography dose index (1) and dose area product (2). (iii) Monte Carlo simulations (2).
CONCLUSION
CBCT of extremities, cervical spine, ears and paranasal sinuses was found to be a low-dose volumetric imaging technique. Effective doses varied significantly because of different exposure settings of CBCT-units and different dosimetry systems used to estimate dose.
Topics: Cone-Beam Computed Tomography; Head; Humans; Neck; Radiation Dosage
PubMed: 29869227
DOI: 10.1007/s11547-018-0910-7 -
Radiotherapy and Oncology : Journal of... Nov 2021Patients with locally advanced cervical cancer (LACC) treated with chemoradiation often experience hematologic toxicity (HT), as chemoradiation can induce bone marrow... (Review)
Review
Correlations between bone marrow radiation dose and hematologic toxicity in locally advanced cervical cancer patients receiving chemoradiation with cisplatin: a systematic review.
Patients with locally advanced cervical cancer (LACC) treated with chemoradiation often experience hematologic toxicity (HT), as chemoradiation can induce bone marrow (BM) suppression. Studies on the relationship between BM dosimetric parameters and clinically significant HT might provide relevant indices for developing BM sparing (BMS) radiotherapy techniques. This systematic review studied the relationship between BM dose and HT in patients with LACC treated with primary cisplatin-based chemoradiation. A systematic search was conducted in Embase, Medline, and Web of Science. Eligibility criteria were treatment of LACC-patients with cisplatin-based chemoradiation and report of HT or complete blood cell count (CBC). The search identified 1346 papers, which were screened on title and abstract before two reviewers independently evaluated the full-text. 17 articles were included and scored according to a selection of the TRIPOD criteria. The mean TRIPOD score was 12.1 out of 29. Fourteen studies defining BM as the whole pelvic bone contour (PB) detected significant associations with V10 (3/14), V20 (6/14), and V40 (4/11). Recommended cut-off values were V10 > 95-75%, V20 > 80-65%, and V40 > 37-28%. The studies using lower density marrow spaces (PBM) or active bone marrow (ABM) as a proxy for BM only found limited associations with HT. Our study was the first literature review providing an overview of articles evaluating the correlation between BM and HT for patients with LACC undergoing cisplatin-based chemoradiation. There is a scarcity of studies independently validating developed prediction models between BM dose and HT. Future studies may use PB contouring to develop normal tissue complication probability models.
Topics: Bone Marrow; Chemoradiotherapy; Cisplatin; Female; Humans; Radiation Dosage; Radiotherapy Dosage; Radiotherapy, Intensity-Modulated; Uterine Cervical Neoplasms
PubMed: 34560187
DOI: 10.1016/j.radonc.2021.09.009