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Seminars in Radiation Oncology Apr 2016Patients with tumors adjacent to the optic nerves and chiasm are frequently not candidates for single-fraction stereotactic radiosurgery (SRS) due to concern for... (Review)
Review
Patients with tumors adjacent to the optic nerves and chiasm are frequently not candidates for single-fraction stereotactic radiosurgery (SRS) due to concern for radiation-induced optic neuropathy. However, these patients have been successfully treated with hypofractionated SRS over 2-5 days, though dose constraints have not yet been well defined. We reviewed the literature on optic tolerance to radiation and constructed a dose-response model for visual pathway tolerance to SRS delivered in 1-5 fractions. We analyzed optic nerve and chiasm dose-volume histogram (DVH) data from perioptic tumors, defined as those within 3mm of the optic nerves or chiasm, treated with SRS from 2000-2013 at our institution. Tumors with subsequent local progression were excluded from the primary analysis of vision outcome. A total of 262 evaluable cases (26 with malignant and 236 with benign tumors) with visual field and clinical outcomes were analyzed. Median patient follow-up was 37 months (range: 2-142 months). The median number of fractions was 3 (1 fraction n = 47, 2 fraction n = 28, 3 fraction n = 111, 4 fraction n = 10, and 5 fraction n = 66); doses were converted to 3-fraction equivalent doses with the linear quadratic model using α/β = 2Gy prior to modeling. Optic structure dose parameters analyzed included Dmin, Dmedian, Dmean, Dmax, V30Gy, V25Gy, V20Gy, V15Gy, V10Gy, V5Gy, D50%, D10%, D5%, D1%, D1cc, D0.50cc, D0.25cc, D0.20cc, D0.10cc, D0.05cc, D0.03cc. From the plan DVHs, a maximum-likelihood parameter fitting of the probit dose-response model was performed using DVH Evaluator software. The 68% CIs, corresponding to one standard deviation, were calculated using the profile likelihood method. Of the 262 analyzed, 2 (0.8%) patients experienced common terminology criteria for adverse events grade 4 vision loss in one eye, defined as vision of 20/200 or worse in the affected eye. One of these patients had received 2 previous courses of radiotherapy to the optic structures. Both cases were meningiomas treated with 25Gy in 5 fractions, with a 3-fraction equivalent optic nerve Dmax of 19.2 and 22.2Gy. Fitting these data to a probit dose-response model enabled risk estimates to be made for these previously unvalidated optic pathway constraints: the Dmax limits of 12Gy in 1 fraction from QUANTEC, 19.5Gy in 3 fractions from Timmerman 2008, and 25Gy in 5 fractions from AAPM Task Group 101 all had less than 1% risk. In 262 patients with perioptic tumors treated with SRS, we found a risk of optic complications of less than 1%. These data support previously unvalidated estimates as safe guidelines, which may in fact underestimate the tolerance of the optic structures, particularly in patients without prior radiation. Further investigation would refine the estimated normal tissue complication probability for SRS near the optic apparatus.
Topics: Dose Fractionation, Radiation; Humans; Models, Theoretical; Radiation Dose Hypofractionation; Radiation Injuries; Radiation Tolerance; Radiosurgery; Radiotherapy Dosage; Visual Pathways
PubMed: 27000505
DOI: 10.1016/j.semradonc.2015.11.008 -
International Journal of Radiation... Dec 2020
Review
Topics: Breast Neoplasms; Dose Fractionation, Radiation; Humans; Mastectomy; Randomized Controlled Trials as Topic; United Kingdom
PubMed: 33220220
DOI: 10.1016/j.ijrobp.2020.06.064 -
Progress in Neurological Surgery 2007The effects of radiosurgery on brain tumor tissue remain to be defined. Effects are dose, volume, time, and tumor histology dependent. In this report, we discuss data... (Review)
Review
The effects of radiosurgery on brain tumor tissue remain to be defined. Effects are dose, volume, time, and tumor histology dependent. In this report, we discuss data from resected specimens after radiosurgery, and work to develop a classification method for radiosurgery effects.
Topics: Brain Diseases; Dose Fractionation, Radiation; Dose-Response Relationship, Drug; Humans; Radiation Protection; Radiosurgery
PubMed: 17317973
DOI: 10.1159/000100092 -
Seminars in Radiation Oncology Apr 2016Pancreatic carcinoma is an aggressive disease and radiotherapy treatment delivery to the primary tumor is constrained by the anatomical close location of the duodenum,... (Review)
Review
Pancreatic carcinoma is an aggressive disease and radiotherapy treatment delivery to the primary tumor is constrained by the anatomical close location of the duodenum, stomach, and small bowel. Duodenal dose tolerance for radiosurgery in 2-5 fractions has been largely unknown. The literature was surveyed for quantitative models of risk in 1-5 fractions and we analyzed our own patient population of 44 patients with unresectable pancreatic tumors who received 3 or 5 fractions of stereotactic body radiotherapy (SBRT) between March 2009 and March 2013. A logistic model was constructed in the dose-volume histogram (DVH) Evaluator software for the duodenal D50%, D30cc, D5cc, D1cc, and maximum point dose D0.035cc. Dose tolerance limits from the literature were overlaid onto the clinical duodenal data in the form of a DVH Risk Map, with risk levels of the published limits estimated from the model of clinical data. In 3 fractions, Kopek 2010 found a statistically significant difference in D1cc of patients with no common terminology criteria for adverse events (CTCAE) v3 grade 2 or higher duodenal complications (mean D1cc = 25.3Gy) as compared with patients with grade 2 or higher toxicity (mean D1cc = 37.4Gy). From the logistic model of our duodenal data in 3 fractions, D1cc = 25.3Gy had 4.7% risk of grade 3-4 hemorrhage or stricture and D1cc = 37.4Gy had 20% risk. The 10% risk level was D1cc = 31.4Gy and we were able to keep duodenum dose for all our patients later this level.
Topics: Dose Fractionation, Radiation; Dose-Response Relationship, Radiation; Duodenum; Humans; Pancreatic Neoplasms; Radiation Tolerance; Radiosurgery; Radiotherapy Dosage
PubMed: 27000512
DOI: 10.1016/j.semradonc.2015.12.002 -
Investigation of irradiated volume in linac-based brain hypo-fractionated stereotactic radiotherapy.Radiation Oncology (London, England) Jul 2017Emerging techniques such as brain hypo-fractionated radiotherapy (HF-RT) involve complex cases with limited guidelines for plan quality and normal tissue tolerances. The...
BACKGROUND
Emerging techniques such as brain hypo-fractionated radiotherapy (HF-RT) involve complex cases with limited guidelines for plan quality and normal tissue tolerances. The purpose of the present study was to statistically parameterize irradiated volume independently of dose prescription, or margin to determine what spread in achievable irradiated volume one may expect for a given case.
METHODS
We defined EXT as the total tissue within the external contour of the patient (including the target) and we defined BMP as the contour of the brain minus PTV. Irradiated volumes of EXT and BMP at specific doses (i.e. 50, 60%, etc., of the prescribed dose) were extracted from 135 single-target HF-RT clinical cases, each planned with a single-arc, homogeneous (SAHO) approach in which target maximum dose (Dmax) was constrained to <130% of the prescribed dose. Irradiated volumes were subsequently measured for cases involving 2 targets (N = 29), 3 targets (N = 7) and >3 targets (N = 10) to investigate the effect of target number. We also examined the effect of shape complexity. A series of best fit curves with confidence and prediction intervals were generated for irradiated volume versus total target volume and the resulting model was subsequently validated on a subsequent set of 23 consecutive prospective cases not originally used in curve-fitting. A subset of 30 HF-RT cases were re-planned with a well-published four-arc, heterogeneous (FAHE) radiosurgery planning approach (Dmax could exceed 130%) to demonstrate how technique affects irradiated volume.
RESULTS
For SAHO, strong correlation (R > 0.98) was found for predicting irradiated volumes. For a given total target volume, irradiated-volume increased by a range of 1.4-2.9× for >3 versus single-targets depending on isodose level. Shape complexity had minor impact on irradiated volume. There was no statistical difference in irradiated volumes between validation and input data (p > 0.2). The FAHE-generated irradiated volumes yielded curves and prediction and confidence bands that agreed well with published data indicating that the proposed approach is feasible for cross-institutional comparisons.
CONCLUSIONS
A description of irradiated volume for linac-based HF-RT is proposed based on population data. We have demonstrated that the proposed approach is feasible for inter and intra-institutional comparisons.
Topics: Brain; Dose Fractionation, Radiation; Humans; Radiosurgery; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted
PubMed: 28709427
DOI: 10.1186/s13014-017-0853-5 -
International Journal of Radiation... Mar 2012
Topics: Breast Neoplasms; Dose Fractionation, Radiation; Female; Fiducial Markers; Four-Dimensional Computed Tomography; Humans; Movement; Radiotherapy, Image-Guided; Respiration
PubMed: 22385703
DOI: 10.1016/j.ijrobp.2011.11.048 -
International Journal of Radiation... Mar 2010Publications relating brainstem radiation toxicity to quantitative dose and dose-volume measures derived from three-dimensional treatment planning were reviewed. Despite... (Meta-Analysis)
Meta-Analysis Review
Publications relating brainstem radiation toxicity to quantitative dose and dose-volume measures derived from three-dimensional treatment planning were reviewed. Despite the clinical importance of brainstem toxicity, most studies reporting brainstem effects after irradiation have fewer than 100 patients. There is limited evidence relating toxicity to small volumes receiving doses above 60-64 Gy using conventional fractionation and no definitive criteria regarding more subtle dose-volume effects or effects after hypofractionated treatment. On the basis of the available data, the entire brainstem may be treated to 54 Gy using conventional fractionation using photons with limited risk of severe or permanent neurological effects. Smaller volumes of the brainstem (1-10 mL) may be irradiated to maximum doses of 59 Gy for dose fractions
64 Gy. Topics: Adult; Age Factors; Brain Stem; Child; Dose Fractionation, Radiation; Dose-Response Relationship, Radiation; Humans; Maximum Tolerated Dose; Photons; Protons; Radiation Injuries; Radiation Tolerance; Radiotherapy Planning, Computer-Assisted
PubMed: 20171516
DOI: 10.1016/j.ijrobp.2009.08.078 -
Rays 2004Surgery remains the main procedure for rectal cancer therapy. However, in the past decades various radiation therapy modalities were used to improve outcomes. The... (Review)
Review
Surgery remains the main procedure for rectal cancer therapy. However, in the past decades various radiation therapy modalities were used to improve outcomes. The optimization of the clinical results of radiotherapy alone with concomitant boost or hyperfractionated, accelerated radiotherapy or chemoradiation requires a better understanding of biological evidences on RT effect, considering the possible presentation of this tumor: "visible" unresectable, "visible" resectable and subclinical disease. Furthermore, parameters as tumor volume, hypoxic fraction, intrinsic radiosensitivity, doubling time and clonogen proliferation are factors shown to have an impact on tumor control probability.
Topics: Dose Fractionation, Radiation; Humans; Radiotherapy Dosage; Rectal Neoplasms; Relative Biological Effectiveness
PubMed: 15603308
DOI: No ID Found -
Neuro-oncology Apr 2017Stereotactic radiosurgery (SRS), typically administered in a single session, is widely employed to safely, efficiently, and effectively treat small intracranial lesions....
Stereotactic radiosurgery (SRS), typically administered in a single session, is widely employed to safely, efficiently, and effectively treat small intracranial lesions. However, for large lesions or those in close proximity to critical structures, it can be difficult to obtain an acceptable balance of tumor control while avoiding damage to normal tissue when single-fraction SRS is utilized. Treating a lesion in 2 to 5 fractions of SRS (termed "hypofractionated SRS" [HF-SRS]) potentially provides the ability to treat a lesion with a total dose of radiation that provides both adequate tumor control and acceptable toxicity. Indeed, studies of HF-SRS in large brain metastases, vestibular schwannomas, meningiomas, and gliomas suggest that a superior balance of tumor control and toxicity is observed compared with single-fraction SRS. Nonetheless, a great deal of effort remains to understand radiobiologic mechanisms for HF-SRS driving the dose-volume response relationship for tumors and normal tissues and to utilize this fundamental knowledge and the results of clinic studies to optimize HF-SRS. In particular, the application of HF-SRS in the setting of immunomodulatory cancer therapies offers special challenges and opportunities.
Topics: Brain Neoplasms; Clinical Trials as Topic; Dose Fractionation, Radiation; Glioblastoma; Humans; Meningeal Neoplasms; Meningioma; Neuroma, Acoustic; Radiation Dose Hypofractionation; Radiosurgery; Treatment Outcome
PubMed: 28380634
DOI: 10.1093/neuonc/now301 -
Annals of the ICRP Jun 2015Tissue effects of radiation exposure are observed in virtually all normal tissues, with interactions when several organs are involved. Early reactions occur in turnover...
Tissue effects of radiation exposure are observed in virtually all normal tissues, with interactions when several organs are involved. Early reactions occur in turnover tissues, where proliferative impairment results in hypoplasia; late reactions, based on combined parenchymal, vascular, and connective tissue changes, result in loss of function within the exposed volume; consequential late effects develop through interactions between early and late effects in the same organ; and very late effects are dominated by vascular sequelae. Invariably, involvement of the immune system is observed. Importantly, latent times of late effects are inversely dependent on the biologically equieffective dose. Each tissue component and--importantly--each individual symptom/endpoint displays a specific dose-effect relationship. Equieffective doses are modulated by exposure conditions: in particular, dose-rate reduction--down to chronic levels--and dose fractionation impact on late responding tissues, while overall exposure time predominantly affects early (and consequential late) reactions. Consequences of partial organ exposure are related to tissue architecture. In 'tubular' organs (gastrointestinal tract, but also vasculature), punctual exposure affects function in downstream compartments. In 'parallel' organs, such as liver or lungs, only exposure of a significant (organ-dependent) fraction of the total volume results in clinical consequences. Forthcoming studies must address biomarkers of the individual risk for tissue reactions, and strategies to prevent/mitigate tissue effects after exposure.
Topics: Dose Fractionation, Radiation; Dose-Response Relationship, Radiation; Environmental Exposure; Humans; Occupational Exposure; Radiation Injuries; Radiation Monitoring; Radiation Protection; Radiation, Ionizing; Radioactive Hazard Release; Radiometry; Risk Assessment
PubMed: 25816259
DOI: 10.1177/0146645314560686