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An International Expert Survey on the Indications and Practice of Radical Thoracic Reirradiation for Non-Small Cell Lung Cancer. Adv Radiat Oncol 2021; 6:100653. [PMID: 33851065 PMCID: PMC8022147 DOI: 10.1016/j.adro.2021.100653] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 12/09/2020] [Accepted: 01/09/2021] [Indexed: 12/25/2022] Open
Abstract
Purpose Thoracic reirradiation for non-small cell lung cancer with curative intent is potentially associated with severe toxicity. There are limited prospective data on the best method to deliver this treatment. We sought to develop expert consensus guidance on the safe practice of treating non-small cell lung cancer with radiation therapy in the setting of prior thoracic irradiation. Methods and Materials Twenty-one thoracic radiation oncologists were invited to participate in an international Delphi consensus process. Guideline statements were developed and refined during 4 rounds on the definition of reirradiation, selection of appropriate patients, pretreatment assessments, planning of radiation therapy, and cumulative dose constraints. Consensus was achieved once ≥75% of respondents agreed with a statement. Statements that did not reach consensus in the initial survey rounds were revised based on respondents’ comments and re-presented in subsequent rounds. Results Fifteen radiation oncologists participated in the 4 surveys between September 2019 and March 2020. The first 3 rounds had a 100% response rate, and the final round was completed by 93% of participants. Thirty-three out of 77 statements across all rounds achieved consensus. Key recommendations are as follows: (1) appropriate patients should have a good performance status and can have locally relapsed disease or second primary cancers, and there are no absolute lung function values that preclude reirradiation; (2) a full diagnostic workup should be performed in patients with suspected local recurrence and; (3) any reirradiation should be delivered using optimal image guidance and highly conformal techniques. In addition, consensus cumulative dose for the organs at risk in the thorax are described. Conclusions These consensus statements provide practical guidance on appropriate patient selection for reirradiation, appropriate radiation therapy techniques, and cumulative dose constraints.
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A simple approximation for the evaluation of the photon iso-effective dose in Boron Neutron Capture Therapy based on dose-independent weighting factors. Appl Radiat Isot 2020; 157:109018. [DOI: 10.1016/j.apradiso.2019.109018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 11/27/2019] [Accepted: 12/03/2019] [Indexed: 11/23/2022]
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Chargari C, Maroun P, Louvel G, Drouet M, Riccobono D, François S, Dhermain F, Cosset JM, Deutsch É. [Repair and time-dose factor: The example of spinal cord irradiation]. Cancer Radiother 2017; 21:547-553. [PMID: 28888745 DOI: 10.1016/j.canrad.2017.07.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 07/05/2017] [Indexed: 01/31/2023]
Abstract
The question whether a reirradiation is possible, with either curative of palliative intent, is a frequent issue and a true therapeutic challenge, in particular for a critical organ sensitive to cumulative dose, such as the spinal cord. Preclinical experimental data, based on debatable models that are hardly transferable to patients, suggest that there is a possibility of reirradiation, beyond the classical threshold for dose constraints, taking into account the "time-dose factor". Although the underlying biological mechanisms are however uncertain, scarce clinical data seem to confirm that the tolerance of spinal cord to reirradiation does exist, provided that a particular attention to total dose is given. In the context where modern stereotactic irradiation facilities expand therapeutic perspectives, we review the literature on possibilities of reirradiation, through the example of spinal cord reirradiation.
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Affiliation(s)
- C Chargari
- Département de radiothérapie, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Université Paris-Saclay, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Radiothérapie moléculaire UMR 1030, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Effets biologiques des rayonnements, Institut de recherche biomédicale des armées, D19, 91220 Brétigny-sur-Orge, France; École du Val-de-Grâce, place Alphonse-Laveran, 75005 Paris, France.
| | - P Maroun
- Département de radiothérapie, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Université Paris-Saclay, 114, rue Édouard-Vaillant, 94800 Villejuif, France
| | - G Louvel
- Département de radiothérapie, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Université Paris-Saclay, 114, rue Édouard-Vaillant, 94800 Villejuif, France
| | - M Drouet
- Effets biologiques des rayonnements, Institut de recherche biomédicale des armées, D19, 91220 Brétigny-sur-Orge, France
| | - D Riccobono
- Effets biologiques des rayonnements, Institut de recherche biomédicale des armées, D19, 91220 Brétigny-sur-Orge, France
| | - S François
- Effets biologiques des rayonnements, Institut de recherche biomédicale des armées, D19, 91220 Brétigny-sur-Orge, France
| | - F Dhermain
- Département de radiothérapie, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Université Paris-Saclay, 114, rue Édouard-Vaillant, 94800 Villejuif, France
| | - J-M Cosset
- Centre Charlebourg-La Défense, groupe Amethyst, 65, avenue Foch, 92250 La Garenne-Colombes, France
| | - É Deutsch
- Département de radiothérapie, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Université Paris-Saclay, 114, rue Édouard-Vaillant, 94800 Villejuif, France; Radiothérapie moléculaire UMR 1030, Gustave-Roussy Cancer Campus, 114, rue Édouard-Vaillant, 94800 Villejuif, France
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Jain AK, Yamada YJ. The role of stereotactic body radiotherapy and stereotactic radiosurgery in the re-irradiation of metastatic spinal tumors. Expert Rev Anticancer Ther 2014; 14:1141-52. [PMID: 25066490 DOI: 10.1586/14737140.2014.940326] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) are advanced radiotherapy delivery techniques that allow for the delivery of high-dose per fraction radiation. Advances in imaging technology and intensity modulation have allowed SRS and SBRT to be used for the treatment of tumors in close proximity to the spinal cord and cauda equina, in particular spinal metastases. While the initial treatment of spinal metastases is often conventional palliative radiotherapy, treatment failure is not uncommon, and conventional re-irradiation may not be feasible due to spinal cord tolerance. SBRT and SRS have emerged as important techniques for the treatment of spinal metastases in the proximity of previously irradiated spinal cord. Here we review the current data on the use of SBRT and SRS spinal re-irradiation, and future directions for these important treatment modalities.
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Affiliation(s)
- Anshu K Jain
- Department of Radiation Oncology, Columbia University Medical Center and New York Presbyterian Hospital, 622 W. 168th St, New York, NY 10032, USA
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Lee AWM, Fee WE, Ng WT, Chan LK. Nasopharyngeal carcinoma: salvage of local recurrence. Oral Oncol 2012; 48:768-74. [PMID: 22425246 DOI: 10.1016/j.oraloncology.2012.02.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 02/16/2012] [Accepted: 02/17/2012] [Indexed: 10/28/2022]
Abstract
Local control of nasopharyngeal carcinoma has substantially improved with advancing radiotherapy technology and appropriate combination with chemotherapy. However, when local recurrence occurs, this is one of the most difficult challenges. Aggressive treatment is indicated because long term salvage is achievable particularly for early recurrence, but high risk of complications is a serious concern. Treatment options include different methods of surgery and/or re-irradiation with/without chemotherapy. Available information in the literature is grossly inadequate; most reports compose of small series of highly selected patients with heterogeneous characteristics and treatment. No randomized trials have been performed to evaluate the therapeutic ratio of different treatment methods. This article reviews available treatment options, their therapeutic benefits and risks of complications; the objective is to provide information for developing treatment recommendations and suggestions for future improvement.
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Affiliation(s)
- Anne W M Lee
- Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong.
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Sahgal A, Ma L, Weinberg V, Gibbs IC, Chao S, Chang UK, Werner-Wasik M, Angelov L, Chang EL, Sohn MJ, Soltys SG, Létourneau D, Ryu S, Gerszten PC, Fowler J, Wong CS, Larson DA. Reirradiation Human Spinal Cord Tolerance for Stereotactic Body Radiotherapy. Int J Radiat Oncol Biol Phys 2012; 82:107-16. [PMID: 20951503 DOI: 10.1016/j.ijrobp.2010.08.021] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 06/22/2010] [Accepted: 08/12/2010] [Indexed: 10/18/2022]
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Spinal cord tolerance to reirradiation with single-fraction radiosurgery: a swine model. Int J Radiat Oncol Biol Phys 2011; 83:1031-7. [PMID: 22197239 DOI: 10.1016/j.ijrobp.2011.08.030] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 07/05/2011] [Accepted: 08/24/2011] [Indexed: 12/17/2022]
Abstract
PURPOSE This study was performed to determine swine spinal cord tolerance to single-fraction, partial-volume irradiation 1 year after receiving uniform irradiation to 30 Gy in 10 fractions. METHODS AND MATERIALS A 10-cm length of spinal cord (C3-T1) was uniformly irradiated to 30 Gy in 10 consecutive fractions and reirradiated 1 year later with a single radiosurgery dose centered within the previously irradiated segment. Radiosurgery was delivered to a cylindrical volume approximately 5 cm in length and 2 cm in diameter, which was positioned laterally to the cervical spinal cord, resulting in a dose distribution with the 90%, 50%, and 10% isodose lines traversing the ipsilateral, central, and contralateral spinal cord, respectively. Twenty-three pigs were stratified into six dose groups with mean maximum spinal cord doses of 14.9 ± 0.1 Gy (n = 2), 17.1 ± 0.3 Gy (n = 3), 19.0 ± 0.1 Gy (n = 5), 21.2 ± 0.1 Gy (n = 5), 23.4 ± 0.2 Gy (n = 5), and 25.4 ± 0.4 Gy (n = 3). The mean percentage of spinal cord volumes receiving ≥10 Gy for the same groups were 34% ± 1%, 40% ± 1%, 46% ± 3%, 52% ± 1%, 56 ± 3%, and 57% ± 1%. The study endpoint was motor neurologic deficit as determined by a change in gait during a 1- year follow-up period. RESULTS A steep dose-response curve was observed with a 50% incidence of paralysis (ED(50)) for the maximum point dose of 19.7 Gy (95% confidence interval, 17.4-21.4). With two exceptions, histology was unremarkable in animals with normal neurologic status, while all animals with motor deficits showed some degree of demyelination and focal white matter necrosis on the irradiated side, with relative sparing of gray matter. Histologic comparison with a companion study of de novo irradiated animals revealed that retreatment responders had more extensive tissue damage, including infarction of gray matter, only at prescription doses >20 Gy. CONCLUSION Pigs receiving spinal radiosurgery 1 year after receiving 30 Gy in 10 fractions were not at significantly higher risk of developing motor deficits than pigs that received radiosurgery alone.
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Dilmanian FA, Zhong Z, Bacarian T, Benveniste H, Romanelli P, Wang R, Welwart J, Yuasa T, Rosen EM, Anschel DJ. Interlaced x-ray microplanar beams: a radiosurgery approach with clinical potential. Proc Natl Acad Sci U S A 2006; 103:9709-14. [PMID: 16760251 PMCID: PMC1480471 DOI: 10.1073/pnas.0603567103] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Studies have shown that x-rays delivered as arrays of parallel microplanar beams (microbeams), 25- to 90-microm thick and spaced 100-300 microm on-center, respectively, spare normal tissues including the central nervous system (CNS) and preferentially damage tumors. However, such thin microbeams can only be produced by synchrotron sources and have other practical limitations to clinical implementation. To approach this problem, we first studied CNS tolerance to much thicker beams. Three of four rats whose spinal cords were exposed transaxially to four 400-Gy, 0.68-mm microbeams, spaced 4 mm, and all four rats irradiated to their brains with large, 170-Gy arrays of such beams spaced 1.36 mm, all observed for 7 months, showed no paralysis or behavioral changes. We then used an interlacing geometry in which two such arrays at a 90-degree angle produced the equivalent of a contiguous beam in the target volume only. By using this approach, we produced 90-, 120-, and 150-Gy 3.4 x 3.4 x 3.4 mm(3) exposures in the rat brain. MRIs performed 6 months later revealed focal damage within the target volume at the 120- and 150-Gy doses but no apparent damage elsewhere at 120 Gy. Monte Carlo calculations indicated a 30-microm dose falloff (80-20%) at the edge of the target, which is much less than the 2- to 5-mm value for conventional radiotherapy and radiosurgery. These findings strongly suggest potential application of interlaced microbeams to treat tumors or to ablate nontumorous abnormalities with minimal damage to surrounding normal tissue.
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Affiliation(s)
- F Avraham Dilmanian
- Medical Department, National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973, USA.
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Morris GM, Micca PL, Nawrocky MM, Weissfloch LE, Coderre JA. Long-term infusions of p-boronophenylalanine for boron neutron capture therapy: evaluation using rat brain tumor and spinal cord models. Radiat Res 2002; 158:743-52. [PMID: 12452777 DOI: 10.1667/0033-7587(2002)158[0743:ltiopb]2.0.co;2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Rat 9L gliosarcoma cells infiltrating the normal brain have been shown previously to accumulate only approximately 30% as much boron as the intact tumor after administration of the boronated amino acid p-boronophenylalanine (BPA). Long-term i.v. infusions of BPA were shown previously to increase the boron content of these infiltrating tumor cells significantly. Experiments to determine whether this improved BPA distribution into infiltrating tumor cells after a long-term i.v. infusion improves tumor control after BNCT in this brain tumor model and whether it has any deleterious effects in the response of the rat spinal cord to BNCT are the subjects of the present report. BPA was administered in a fructose solution at a dose of 650 mg BPA/kg by single i.p. injection or by i.v. infusion for 2 h or 6 h, at 330 mg BPA/kg h(-1). At 1 h after the end of either the 2-h or the 6-h infusion, the CNS:blood (10)B partition ratio was 0.9:1. At 3 h after the single i.p. injection, the ratio was 0.6:1. After spinal cord irradiations, the ED(50) for myeloparesis was 14.7 +/- 0.4 Gy after i.p. administration of BPA and 12.9 +/- 0.3 Gy in rats irradiated after a 6-h i.v. infusion of BPA; these values were significantly different (P < 0.001). After irradiation with 100 kVp X rays, the ED(50) was 18.6 +/- 0.1 Gy. The boron compound biological effectiveness (CBE) factors calculated for the boron neutron capture dose component were 1.2 +/- 0.1 for the i.p. BPA administration protocol and 1.5 +/- 0.1 after irradiation using the 6-h i.v. BPA infusion protocol (P < 0.05). In the rat 9L gliosarcoma brain tumor model, the blood boron concentrations at 1 h after the end of the 2-h infusion (330 mg BPA/kg h(-1); n = 15) or after the 6-h infusion (190 mg BPA/kg h(-1); n = 13) were 18.9 +/- 2.2 microg 10B/g and 20.7 +/- 1.8 microg 10B/g, respectively. The irradiation times were adjusted individually, based on the preirradiation blood sample, to deliver a predicted 50% tumor control dose of 8.2 Gy ( approximately 30 photon-equivalent Gy) to all tumors. In the present study, the long-term survival was approximately 50% and was not significantly different between the 2-h and the 6-h infusion groups. The mode of BPA administration and the time between administration and irradiation influence the 10B partition ratio between the CNS and the blood, which in turn influences the measured CBE factor. These findings underline the need for clinical biodistribution studies to be carried out to establish 10B partition ratios as a key component in the evaluation of modified administration protocols involving BPA.
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Affiliation(s)
- G M Morris
- Research Institute (University of Oxford), Churchill Hospital, Oxford, OX3 7LJ, United Kingdom
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Bhatnagar A, Heron DE, Kondziolka D, Lunsford LD, Flickinger JC. Analysis of repeat stereotactic radiosurgery for progressive primary and metastatic CNS tumors. Int J Radiat Oncol Biol Phys 2002; 53:527-32. [PMID: 12062593 DOI: 10.1016/s0360-3016(02)02784-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE To identify and evaluate the pretreatment and patient factors that would predict for complications after repeat radiosurgery. METHODS AND MATERIALS The data from 26 patients who underwent re-irradiation with Gamma Knife surgery after a previous procedure in the same or subjacent location were available for evaluation. The range of follow-up was 1-45 months (mean 10). The mean minimal and maximal initial dose and volume for all 26 patients was 16.2 Gy (range 12-22), 31.0 Gy (range 22.2-40.0), and 12.4 cm(3) (range 1.20-70.84), respectively. The mean marginal and maximal repeated radiosurgery dose and volume for all 26 patients was 14.9 Gy (range 12-22.5), 29.7 Gy (range 18.0-45.0) and 12.8 cm(3) (range 1.10-39.20), respectively. RESULTS Tumor control was significantly better statistically (p = 0.0129) for benign tumors (6 of 6, 100% actuarial rate at 4 years) compared with malignant tumors (7 of 20, 35% actuarial rate at 3 years, 3 of 4 metastatic tumors and 2 of 10 primary malignant gliomas). The retreatment volume for radiosurgery correlated significantly with the probability of neurologic decline (any cause) (p = 0.0181). CONCLUSION Repeat radiosurgery can be performed for recurrent tumors with minimal central nervous system toxicity, especially for benign tumors, with reasonable tumor control.
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Affiliation(s)
- Ajay Bhatnagar
- Department of Radiation Oncology, Center for Image-Guided Neurosurgery, University of Pittsburgh School of Medicine, 200 Lothrop Street, Pittsburgh, PA 15213, USA
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Supe SS, Ganesh K, Velmurugan J, Rana B, Sankar B. Radiobiological considerations of re-irradiation tolerance of the spinal cord. Rep Pract Oncol Radiother 2002. [DOI: 10.1016/s1507-1367(02)70982-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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van Luijk P, Bijl HP, Coppes RP, van der Kogel AJ, Konings AW, Pikkemaat JA, Schippers JM. Techniques for precision irradiation of the lateral half of the rat cervical spinal cord using 150 MeV protons [corrected]. Phys Med Biol 2001; 46:2857-71. [PMID: 11720351 DOI: 10.1088/0031-9155/46/11/307] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Techniques for high precision irradiation experiments with protons, to investigate the volume dependence of the tolerance dose of the rat cervical spinal cord are described. In the present study, 50% of the lateral cross section of the spinal cord was irradiated. The diameter of the cross section of this part of the rat spinal cord is at maximum 3.5 mm. Therefore, a dedicated procedure was developed to comply with the needs for a very high positioning accuracy and high spatial resolution dosimetry. By using 150 MeV protons a steep dose gradient (20-80% = 1 mm) in the centre of the spinal cord was achieved. This yields a good dose contrast between the left and right halves of the cord. A home-made digital x-ray imager with a pixel resolution of 0.18 mm/pixel was used for position verification of the spinal cord. A positioning accuracy of 0.09 mm was obtained by using information of multiple pixels. The average position stability during the irradiation was found to be 0.08 mm (1 SD) without significant systematic deviations. Profiles of the dose distribution were measured with a 2D dosimetry system consisting of a scintillating screen and a CCD camera. Dose volume histograms of the whole spinal cord as well as separately of the white and grey matters were calculated using MRI imaging of the cross section of the rat cervical spinal cord. From the irradiation of 20 animals a dose-response curve has been established. MRI showed radiation-induced damage at the high dose side of the spinal cord. Analysis of the preliminary dose-response data shows a significant dose-volume effect. With the described procedure and equipment it is possible to perform high precision irradiations on selected parts of the spinal cord.
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Affiliation(s)
- P van Luijk
- Kernfysisch Versneller Instituut, Groningen, The Netherlands
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Abstract
There are increasing requests for delivering a second course of radiation to patients who develop second primary tumors within or close to previous radiotherapy portal or late in-field recurrences. Rational treatment decisions demand rather precise knowledge on long-term recovery of occult radiation injury in various organs. This article summarizes available experimental and clinical data on the effects of reirradiation to the skin, mucosa, gut, lung, spinal cord, brain, heart, bladder, and kidney. The data reveal that, in general, acutely responding tissues recover radiation injury within a few months and, therefore, can tolerate another full course of radiation. For late toxicity endpoints, however, tissues vary considerably in their capacity to recover from occult radiation damage. The heart, bladder, and kidney do not exhibit long-term recovery at all. In contrast, the skin, mucosa, lung, and spinal cord do recover subclinical injury partially to a magnitude dependent on the organ type, size of the initial dose, and, to a lesser extent, the interval between radiation courses. The available clinical data have inspired many radiation oncologists to undertake systematic studies addressing the efficacy and toxicity of reirradiation in various clinical settings. Hopefully, systematic scoring, collection, and analysis of patient outcome will produce quantitative data useful for clinical practice.
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Affiliation(s)
- C Nieder
- Department of Radiation Oncology, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030, USA
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Lee AW, Foo W, Law SC, Peters LJ, Poon YF, Chappell R, Sze WM, Tung SY, Lau WH, Ho JH. Total biological effect on late reactive tissues following reirradiation for recurrent nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys 2000; 46:865-72. [PMID: 10705007 DOI: 10.1016/s0360-3016(99)00512-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
PURPOSE To assess the additional damage of normal tissues attributable to reirradiation and the magnitude of partial recovery following the initial course. METHODS AND MATERIALS Symptomatic late complication rates (excluding xerostomia) in 3635 patients receiving one course (Group 1) and 487 patients receiving two courses of external radiotherapy (Group 2) for nasopharyngeal carcinoma were retrospectively analyzed and compared. RESULTS Group 2 had significantly lower actuarial complication-free survival rates than Group 1: 48% versus 81% at 5 years. The post-retreatment incidence was significantly affected by biologically effective dose (BED) (assuming an alpha/beta ratio of 3 Gy) of the first course: hazard ratio (HR) = 1.04 per Gy(3) (p = 0.01), but only marginally by that of the second course: HR = 1.01 per Gy(3) (p = 0.06). If the summated BED was taken as the dose unit, it was estimated that a total BED of 143 Gy(3) would induce a 20% incidence at 5 years, while the corresponding dose projected from Group 1 was 111 Gy(3). The gap effect was insignificant in the overall analyses, but a trend of decreasing risk with increasing interval was observed in patients with gap > or = 2 years: HR = 0.86 per year (p = 0.07). CONCLUSION The major determinant of post-retreatment complication is the severity of damage during the initial course. The sum of total doses tolerated is higher than that expected with a single-course treatment, suggesting occurrence of partial recovery (particularly in those reirradiated after an interval of 2 years or more).
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Affiliation(s)
- A W Lee
- Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Chai Wan, Hong Kong.
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Ryu S, Gorty S, Kazee AM, Bogart J, Hahn SS, Dalal PS, Chung CT, Sagerman RH. 'Full dose' reirradiation of human cervical spinal cord. Am J Clin Oncol 2000; 23:29-31. [PMID: 10683070 DOI: 10.1097/00000421-200002000-00007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
With the progress of modern multimodality cancer treatment, retreatment of late recurrences or second tumors became more commonly encountered in management of patients with cancer. Spinal cord retreatment with radiation is a common problem in this regard. Because radiation myelopathy may result in functional deficits, many oncologists are concerned about radiation-induced myelopathy when retreating tumors located within or immediately adjacent to the previous radiation portal. The treatment decision is complicated because it requires a pertinent assessment of prognostic factors with and without reirradiation, radiobiologic estimation of recovery of occult spinal cord damage from the previous treatment, as well as interactions because of multimodality treatment. Recent studies regarding reirradiation of spinal cord in animals using limb paralysis as an endpoint have shown substantial and almost complete recovery of spinal cord injury after a sufficient time after the initial radiotherapy. We report a case of "full" dose reirradiation of the entire cervical spinal cord in a patient who has not developed clinically detectable radiation-induced myelopathy on long-term follow-up of 17 years after the first radiotherapy and 5 years after the second radiotherapy.
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Affiliation(s)
- S Ryu
- Department of Radiation Oncology, SUNY Health Science Center, Syracuse, New York, USA
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Morris GM, Coderre JA, Hopewell JW, Micca PL, Wielopolski L. Boron neutron capture therapy: re-irradiation response of the rat spinal cord. Radiother Oncol 1998; 48:313-7. [PMID: 9925251 DOI: 10.1016/s0167-8140(98)00060-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
PURPOSE To evaluate the retreatment response of the CNS to BNC irradiation using a rat spinal cord model. MATERIALS AND METHODS Fischer 344 rats were irradiated with single doses of 6 MeV X-rays which were 22, 40 or 80% of a total effect (TE). An additional group of rats was irradiated with a single exposure of thermal neutrons in the presence of the neutron capture agent boronophenylalanine (BPA) to a dose that represented 82% of the TE. After an interval of 26 weeks, animals were re-irradiated using various single doses of thermal neutrons in combination with BPA. RESULTS The re-irradiation ED50 doses represented 77, 80 or 50% of the TE after an initial X-ray dose of 22, 40 or 80% of the TE, respectively. The re-irradiation ED50 dose was 55% of the TE after an initial BNC irradiation dose representing 82% of the TE. CONCLUSION The level of the initial radiation damage had a direct bearing on the re-irradiation response. Recovery following initial treatment with BNC irradiation was similar to that after initial irradiation with X-rays.
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Affiliation(s)
- G M Morris
- Research Institute (University of Oxford), Churchill Hospital, UK
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Benchalal M, Bachaud JM, François P, Alzieu C, Giraud P, David JM, Daly-Schveitzer N. [Hyperfractionated reirradiation after salvage surgery in cervico-facial carcinoma. Result of a pilot study in 14 patients]. Cancer Radiother 1997; 1:68-73. [PMID: 9265536 DOI: 10.1016/s1278-3218(97)84058-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE Between November 1988 and May 1992, 14 patients were enrolled in a pilot study to evaluate the feasibility and results of hyperfractionated reirradiation for the treatment of head and neck recurrences or of second primary tumors developed in a previously irradiated volume. MATERIALS AND METHODS All patients underwent a surgical resection for the treatment of their recurrence or second cancer. Reirradiation was proposed because of positive margins and/or lymph node metastasis with extra-capsular spread. The planned reirradiation dose was 60 Gy over 5 weeks, with two daily fractions of 1.2 Gy delivered 6-8 hours apart. RESULTS Of the 14 patients, 10 received the reirradiation scheduled dose (ie, 60 Gy). All patients experienced an acute mucositis that never led to disruption of the treatment. Ten patients died 3 to 41 months after reirradiation (mean: 14 months), three were disease-free 48 to 71 months after reirradiation and one was alive with local progressive disease 74 months after reirradiation. The overall local control rate within the reirradiated volume was 43%. The 24- and 36-month overall survival rates were 50 and 35%, respectively. Overall, 13 late complications were noted: four were grade 1, seven were grade 2, and two were grade 3. Three patients still alive in September 1993 and whose initial files were available were enrolled in an additional study to assess from dose-volume histograms the cumulative doses delivered by the two irradiations. CONCLUSION Despite poor local control, reirradiation using a hyperfractionation schedule with high dose level is feasible in terms of acute and late toxicity.
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Affiliation(s)
- M Benchalal
- Centre de traitement des tumeurs, CHI de Montfermeil, France
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Morris GM, Coderre JA, Micca PL, Fisher CD, Capala J, Hopewell JW. Central nervous system tolerance to boron neutron capture therapy with p-boronophenylalanine. Br J Cancer 1997; 76:1623-9. [PMID: 9413952 PMCID: PMC2228217 DOI: 10.1038/bjc.1997.607] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A rat spinal cord model was used to evaluate the effects of boron neutron capture irradiation on the central nervous system (CNS), using a range of doses of the boron delivery agent p-boronophenylalanine (BPA). Three doses of BPA 700, 1000 and 1600 mg kg(-1) were used to establish the biodistribution of boron-10 (10B) in blood, spinal cord and brain over a 3-h period after intraperitoneal (i.p.) administration. At the lowest dose of BPA used, blood 10B levels remained relatively stable over the 3-h sampling period. With the two higher doses of BPA, blood 10B concentrations were greatest at 1 h after BPA administration, and thereafter exhibited a biphasic clearance profile. The largest decline in blood 10B levels occurred between 1 and 2 h after i.p. injection and was most pronounced (approximately 45%) in the highest BPA dose group. Considered overall, 10B concentrations were marginally lower in the spinal cord than in the brain. Levels of 10B in both of these organs showed a slow but progressive increase with time after administration of BPA. The 10B concentration ratio for blood relative to CNS tissue increased with BPA dosage and reached a peak value of approximately 10:1 in the highest BPA dose group, at 1 h after i.p. injection. However, at 3 h after injection the 10B concentration ratios had decreased to approximately 3:1 in all of the BPA dose groups. After irradiation with thermal neutrons in combination with BPA at blood 10B concentrations of approximately 42 and approximately 93 microg g(-1), myelopathy developed after latent intervals of 20.0 +/- 0.6 and 20.0 +/- 1.2 weeks respectively. ED50 values (+/- s.e.) for the incidence of myelopathy were calculated from probit-fitted curves, and were 17.5 +/- 0.7 and 25.0 +/- 0.6 Gy after irradiation with thermal neutrons at blood 10B levels of approximately 42 and approximately 93 microg g(-1) respectively. The compound biological effectiveness (CBE) factor values, estimated from these data, were 0.67 +/- 0.23 and 0.48 +/- 0.18 respectively. This compared with a previous estimate of 0.88 +/- 0.14 at a blood 10B concentration of approximately 19 microg g(-1). It was concluded that the value of the CBE factor was not influenced by the level of 10B in the blood, but by the blood:CNS 10B concentration ratio. In effect, the CBE factor decreases as the concentration ratio increases. Simulations using boron neutron capture therapy (BNCT) treatment planning software indicate a significant therapeutic advantage could be obtained in moving to higher BPA doses than those in current clinical use.
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Affiliation(s)
- G M Morris
- Research Institute, University of Oxford, Churchill Hospital, UK
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Morris GM, Coderre JA, Hopewell JW, Micca PL, Fisher C. Boron neutron capture irradiation of the rat spinal cord: effects of variable doses of borocaptate sodium. Radiother Oncol 1996; 39:253-9. [PMID: 8783402 DOI: 10.1016/0167-8140(95)01693-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The Fischer 344 rat spinal cord model has been used to evaluate the response of the central nervous system to boron neutron capture irradiation with variable doses of the neutron capture agent, borocaptate sodium (BSH). Three doses of BSH, 190, 140 and 80 mg/kg body weight, administered by i.p. injection, were used to establish the time course of 10B accumulation in and removal from the blood. After administration of the two lower doses of BSH, blood 10B levels peaked at 0.5 h after injection, with no significant (P > 0.1) change at 1 h after injection. Beyond this time point, levels of 10B in the blood began to decrease after a dose of 80 mg/kg BSH, but remained constant until 3 h after administration after the two higher doses of BSH. Myelopathy developed after latent intervals of 20.4 +/- 0.1, 20.8 +/- 1.4, 15.0 +/- 0.8, 15.4 +/- 0.4 and 15.6 +/- 0.4 weeks, following irradiation with thermal neutrons in combination with BSH at doses of 20, 40, 80, 140 and 190 mg/kg body weight, respectively. The radiation-induced lesion in the spinal cord was white matter necrosis. ED50 values for myelopathy were calculated from probit-fitted dose-effect curves. Expressed as total physical absorbed doses, these values were 20.7 +/- 1.9, 24.9 +/- 1.2, 27.2 +/- 0.9, 28.4 +/- 0.6 and 32.4 +/- 1.9 Gy after irradiation with thermal neutrons in the presence of 20, 40, 80, 140 and 190 mg/kg body weight of BSH, respectively. The compound biological effectiveness (CBE) factor values, estimated from this data, were in the range 0.49-0.55. There was no significant (P > 0.1) variation in the CBE factor for BSH as a function of increasing 10B concentration in the blood. It was concluded that there was no significant synergistic interaction between the low and high linear energy transfer (LET) components of the boron neutron capture (BNC) radiation field.
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Affiliation(s)
- G M Morris
- CRC Normal Tissue Radiobiological Research Group, University of Oxford, Churchill Hospital, UK
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Benchalal M, Bachaud JM, François P, Alzieu C, Giraud P, David JM, Daly-Schveitzer N. Hyperfractionation in the reirradiation of head and neck cancers. Result of a pilot study. Radiother Oncol 1995; 36:203-10. [PMID: 8532907 DOI: 10.1016/0167-8140(95)01620-v] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Between November 1988 and May 1992, 19 patients were enrolled in a pilot study to evaluate feasibility and results of a hyperfractionated reirradiation in the treatment of head and neck recurrences or second primary tumors developed in previously irradiated volume. Patients were divided in two groups according to the initial treatment before reirradiation: group 1 included 14 patients treated with radical surgery and reirradiated because histological evidence of positive margins and/or extra capsular spread of tumor in lymph node metastases; group 2 included five patients treated with three cycles of CDDP-5FU for unresectable tumors and reirradiated because they experienced a complete or good partial (> or = 80%) response after chemotherapy. The reirradiation planned dose was 60 Gy in 5 weeks, with two daily fractions of 1.2 Gy spaced by 6-8 h intervals. Reirradiation was delivered exclusively with photon beams in 17 cases and with a combination of photon and electron beams in two cases. Follow-up ranged from 3 to 45 months with a median of 17 months. Of the 19 patients, 13 received the reirradiation scheduled dose of 60 Gy. For the six remaining patients, the reirradiation doses ranged from 45.6 to 57.6 Gy. All patients experienced an acute mucositis which never led to interruption of treatment. Of the 14 patients of group 1, 10 died 3-41 months after reirradiation (mean: 14 months), three were disease-free 16-37 months after reirradiation and one patient was alive with local progressive disease 39 months after the reirradiation. The overall local control within reirradiated volume was 36% before and 43% after salvage surgery. For all group 1 patients, 12- and 24-month overall survival was 64 and 36%, respectively (mean: 21 months). All patients of group 2 presented a local failure within the reirradiated volume. Three of them died 12, 16 and 25 months after reirradiation, while two of them were alive with progressive disease 25 and 30 months after reirradiation, respectively. The mean survival was 22 months. Overall, 15 late complications were noted: five grade 1, eight grade 2 and two grade 3. There was no lethal complication. Four patients alive in September 1993, and whose initial technical files were available, were enrolled in an additional study to assess the cumulative doses delivered by the two irradiations. Despite disappointing loco-regional control rates, a reirradiation of 60 Gy using a hyperfractionated schedule is feasible in terms of acute and late toxicity.
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Affiliation(s)
- M Benchalal
- Department of Radiotherapy, Centre Claudius Regaud, Toulouse, France
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Dubben HH. Is there evidence for long-term recovery in the human spinal cord? Regarding Wong et al., IJROBP 30:575-581; 1994. Int J Radiat Oncol Biol Phys 1995; 32:554. [PMID: 7751199 DOI: 10.1016/0360-3016(95)98587-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Lavey RS, Taylor JM, Tward JD, Li LT, Nguyen AA, Chon Y, McBride WH. The extent, time course, and fraction size dependence of mouse spinal cord recovery from radiation injury. Int J Radiat Oncol Biol Phys 1994; 30:609-17. [PMID: 7928492 DOI: 10.1016/0360-3016(92)90947-g] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
PURPOSE This experiment was designed to assess: (a) the influence of fraction size and time interval between fractions on the tolerance of the spinal cord to high cumulative doses of radiation; and (b) the influence of the long-term recovery process on the tolerance of the spinal cord to reirradiation. METHODS AND MATERIALS The T10-L2 level of the spinal cord of C3Hf mice was irradiated using a conventionally fractionated regimen of 2.0 Gy once daily, a prolonged fractionated regimen of 1.2 Gy once daily, a hyperfractionated regimen of 1.2 Gy twice daily, or a single dose of 12 Gy followed 0-190 days later by a second dose of 5-20 Gy. Mice in the multifractionated regimen groups were given a single 15 Gy top-up dose 24 h after reaching a cumulative fractionated dose of 24-70 Gy. Hind limb strength was measured weekly for 2 years after the completion of irradiation. RESULTS Paralysis occurred in a bimodal time distribution, with peaks at 5-10 months and 15-23 months after the completion of irradiation. The cumulative radiation dose was directly associated with the incidence of paralysis in each radiation schedule (p < 0.0001) and inversely associated with the time to onset of paralysis in the 1.2 Gy b.i.d. (p = 0.0001) and 2.0 Gy q.d. schedules (p = 0.03). The median latency of paralysis in each group was inversely associated with the incidence of paralysis in that group (p < 0.001). Decreasing the fraction size from 2.0 to 1.2 Gy once daily markedly increased the radiation tolerance of the spinal cord (p < 0.0001), consistent with a very small alpha-beta value of -0.30 Gy (approximately 95% confidence interval -0.72, +0.18) in the linear-quadratic model. Decreasing the time interval from 24 h to alternating 8 and 16 h periods produced an offsetting diminuation in cord tolerance (p < 0.0001). The 1.2 Gy once daily schedule resulted in ED20 and ED50 values that were approximately double those of the 2.0 Gy once daily and the 1.2 Gy twice daily schedules and a relative risk of paralysis from a given dose that was 0.03 times the risk associated with the other two regimens (p < 0.0001). There was no significant difference between the 2.0 Gy once daily and the 1.2 Gy twice daily dose-paralysis curves (p = 0.86). The residual from a single 12 Gy radiation dose was 17% after 190 days, leaving the retreatment ED50 only 10% below the ED50 of previously unirradiated spinal cord. The relative risk of paralysis after 12 Gy plus a second radiation dose decreased from 1.00 with no time interval between doses to 0.51-0.73 with a 0.25, 1 or 3 day interval, 0.32 with a 7 day interval, 0.11 with a 30 day interval, and 0.06 with a 190 day interval. CONCLUSION The increased radiation tolerance of the murine spinal cord produced by decreasing the fraction size from 2.0 to 1.2 Gy was offset by the diminished tolerance produced by decreasing the time interval between fractions from 24 to 8-16 h, resulting in no significant difference in the dose-paralysis curves of conventional and hyperfractionated radiation schedules. The rodent spinal cord eliminates the majority of the occult radiation injury produced by a radiation dose equal to half the ED50 during the months following irradiation. This permits retreatment of previously irradiated spinal cord to high doses without the induction of myelopathy.
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Affiliation(s)
- R S Lavey
- Department of Radiation Oncology, University of California, Los Angeles 90024
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Wong CS, Van Dyk J, Milosevic M, Laperriere NJ. Radiation myelopathy following single courses of radiotherapy and retreatment. Int J Radiat Oncol Biol Phys 1994; 30:575-81. [PMID: 7928488 DOI: 10.1016/0360-3016(92)90943-c] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
PURPOSE To assess the latent time, survival and dose-fractionation factors associated with permanent radiation myelopathy following single and multiple courses of radiotherapy to the spinal cord. METHODS AND MATERIALS A retrospective analysis was undertaken of all patients who were registered at the Princess Margaret Hospital between 1955 and 1985, and who developed permanent radiation myelopathy. There were 22 males and 13 females with ages ranging from 30 to 72 years. Twenty-four patients developed permanent myelopathy after one course of radiation therapy and 11 patients following retreatment. Seven patients had histological confirmation of radiation myelopathy at autopsy. RESULTS The actuarial survival was 14% at 5 years (median: 8.3 months) from the date of diagnosis of radiation myelopathy. Latent times for myelopathy following a single course of treatment (mean: 18.5 months, 7-57 months), were significantly longer than those after reirradiation (mean: 11.4 months, 4-25 months), p = 0.03. There was not a single incident of myelopathy in patients who received fractionated radiotherapy given once daily to an extrapolated response dose (ERD) of < or = 100 Gy2 (equivalent to 50 Gy in 25 daily fractions). Four patients who developed myelopathy after an ERD of < 100 Gy2 were all treated on accelerated fractionation protocols with multiple fractions given per day. Patients who were reirradiated received significantly higher doses (mean ERD of 148 Gy2) than those who had a single course of treatment (mean ERD of 121 Gy2), p = 0.001. CONCLUSION We conclude that the risk of radiation myelopathy following conventionally fractionated radiotherapy to the spinal cord is extremely small; giving multiple fractions per day reduces the spinal cord tolerance; latent time to myelopathy decreases following retreatment; and there is possible long-term recovery of radiation damage in the human spinal cord.
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Affiliation(s)
- C S Wong
- Department of Radiation Oncology, Princess Margaret Hospital/Ontario Cancer Institute, Toronto, Canada
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Morris GM, Coderre JA, Hopewell JW, Micca PL, Nawrocky MM, Liu HB, Bywaters A. Response of the central nervous system to boron neutron capture irradiation: evaluation using rat spinal cord model. Radiother Oncol 1994; 32:249-55. [PMID: 7816943 DOI: 10.1016/0167-8140(94)90024-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The response of the central nervous system to boron neutron capture irradiation, with either p-boronophenylalanine (BPA) or borocaptate sodium (BSH) as neutron capture agents, has been assessed using a rat spinal cord model. The mean latency times for the development of myelopathy after irradiation with the thermal neutron beam-alone, or in combination with BPA or BSH, were 23.7 +/- 0.3, 21.8 +/- 0.4 and 19.6 +/- 0.4 weeks, respectively. The radiation-induced lesion in the spinal cord was characterised by white matter necrosis. Due to the variations in the microdistribution of different neutron capture agents in body tissues, it was considered inappropriate to define the biological effectiveness of the high LET radiation, resulting from the 10B(n, alpha)7Li neutron capture reaction, relative to photon radiation, using the term 'relative biological effectiveness' (RBE). The term 'compound biological effectiveness' (CBE) factor was used as an alternative. ED50 values for the various irradiation modalities were calculated from probit fitted dose effect curves. Expressed as total physical absorbed doses these values were 13.6 +/- 0.4, 30.3 +/- 2.7 and 13.8 +/- 0.5 Gy after irradiation with the thermal neutron beam alone, or the thermal neutron beam in combination with BSH or BPA, respectively. The RBE of the thermal neutron beam was 1.4 +/- 0.04. The microdistribution of the two neutron capture agents played a crucial role in the determination of the overall biological effect, after thermal neutron activation. BSH, which is excluded from the CNS parenchyma by the blood brain barrier, had a low CBE factor value of 0.46 +/- 0.5. BPA, on the other hand, which crosses the blood brain barrier and distributes in the CNS parenchyma, had a higher CBE factor value of 1.33 +/- 0.16.
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Affiliation(s)
- G M Morris
- Research Institute, University of Oxford, Churchill Hospital, UK
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Stewart FA, Oussoren Y, Van Tinteren H, Bentzen SM. Loss of reirradiation tolerance in the kidney with increasing time after single or fractionated partial tolerance doses. Int J Radiat Biol 1994; 66:169-79. [PMID: 8089627 DOI: 10.1080/09553009414551071] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The aim was to determine the influence of initial dose and dose per fractionation on retreatment tolerance of the kidney. Mouse kidney was bilaterally irradiated with various single or fractionated X-ray doses equivalent to about 12-70% of a defined response dose. The mice were retreated with a range of single doses after 2 or 26 weeks. The development of functional kidney damage was followed by monthly testing of clearance of 51CrEDTA until the animals expressed overt renal dysfunction (maximum follow-up 70 weeks after retreatment). Reirradiation tolerance was assessed by probit analysis and Kaplan-Meier actuarial estimates of the incidence of a defined level of renal damage at 40 weeks after retreatment. Doses required to give a 50% incidence of damage (RD50) were compared for animals that had received previous single dose or fractionated irradiations, or that were previously unirradiated. Multivariate analysis of time to expression of renal damage (latency) was also done using the Cox Proportional Hazards model. Results demonstrated that previous irradiation always compromised retreatment tolerance, even for intervals of 26 weeks after initial treatments with < 20% full response dose. Reirradiation tolerance was inversely related to the initial dose and tolerance decreased significantly with increasing interval between treatments, suggesting progression rather than recovery from the initial damage. Linear-quadratic analysis of the data for reirradiation at 26 weeks after partial-response doses gave an alpha/beta = 1.4 Gy. This was significantly lower than the alpha/beta = 3.3 Gy obtained for initial treatments alone (no retreatment), indicating a larger fractionation-sparing effect for the retreatment situation.
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Affiliation(s)
- F A Stewart
- Division of Experimental Therapy, The Netherlands Cancer Institute Antoni van Leeuwenhoek Huis, Amsterdam
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