Estimation of Errors Associated With Use of Linear-Quadratic Formalism for Evaluation of Biologic Equivalence Between Single and Hypofractionated Radiation Doses: An In Vitro Study

Iwata, Hiromitsu; Shibamoto, Yuta; Murata, Rumi; Tomita, Natsuo; Ayakawa, S.; Ogino, Hiroyuki; Ito, Masato

doi:10.1016/j.ijrobp.2008.12.093

Cited by 41 publications

(30 citation statements)

References 32 publications

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“…In Gamma Knife SRS, the dose delivered to the optic pathways is usually limited to 8 -10 Gy, whereas we were able to safely administer 21 Gy in 3 fractions or 25 Gy in 5 fractions in most cases. Although linear quadratic formalism is not applicable to these fractionation schedules, 24,25 21 Gy in 3 fractions corresponds to 13.1 Gy in 1 fraction, assuming an a/b ratio of 3 Gy, and 25 Gy in 5 fractions corresponds to 12.7 Gy. The actual efficacy of hypofractionation is considered to be about 15% higher.…”

Section: Survival and Local Controlmentioning

confidence: 99%

“…The actual efficacy of hypofractionation is considered to be about 15% higher. 24 Therefore, it could be said that 21 Gy in 3 fractions corresponds to 15.1 Gy in 1 fraction, and 25 Gy in 5 fractions corresponds to 14.6 Gy. In vivo, a higher effect of fractionation is expected, especially when reoxygenation of hypoxic cells takes place, 26,27 but this is probably not the case for benign tumors such as PA. At any rate, the biological effects of our fractionation schedules on tumors appear to be stronger than those of the 8-10 Gy dose used in Gamma Knife treatment, which may account for the favorable tumor control rate observed in our study.…”

Section: Survival and Local Controlmentioning

confidence: 99%

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Hypofractionated stereotactic radiotherapy with CyberKnife for nonfunctioning pituitary adenoma: high local control with low toxicity

Iwata¹,

Sato²,

Tatewaki³

et al. 2011

Neuro-Oncology

117

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patients with nonfunctioning pituitary adenoma were treated with hypofractionated SRT. Forty-three patients were male, and 57 were female. The patient's ages ranged from 16 to 82 years (median, 59 years). Five patients were medically inoperable, and 1 refused surgery; the remaining 94 were recurrent cases or those receiving postoperative adjuvant SRT. No patients had a history of previous cranial radiotherapy. Tumor volume ranged from 0.7 to 64.3 mL (median, 5.1 mL). The marginal doses were 17.0 to 21.0 Gy for the 3-fraction schedule and 22.0 to 25.0 Gy for the 5-fraction schedule. Toxicities were evaluated with the Common Terminology Criteria for Adverse Events version 4.0. The median follow-up period for living patients was 33 months (range, 18 -118.5 months). The 3-year overall survival and local control rates were 98% and 98%, respectively. In-field and out-field tumor regrowth were observed in 3 and 2 patients, respectively. Transient cyst enlargement occurred in 3 cases. A post-SRT grade 2 visual disorder occurred in 1 patient. Symptomatic post-SRT hypopituitarism was observed in 3 of 74 patients who had not received hormone replacement therapy after surgery.CyberKnife SRT involving 21 Gy in 3 fractions or 25 Gy in 5 fractions is safe and effective for surgical treatment of nonfunctioning pituitary adenoma. Hypofractionated SRT appears useful for protecting the visual nerve and neuroendocrine function, especially for tumors located near the optic pathways and large tumors.Keywords: CyberKnife, hypofractionated stereotactic radiotherapy, nonfunctioning, optic pathway, pituitary adenoma. P ituitary adenoma (PA) is a benign tumor that occurs mainly in adults between 20 and 50 years of age and constitutes about 10 -20% of all intracranial tumors.1,2 PA is divided into functioning and nonfunctioning varieties, and the purpose and method of treatment differ for the two entities. Treatment for functioning PA aims to prevent the excessive secretion of anterior pituitary lobe hormone. On the other hand, treatment of nonfunctioning PA is typically intended to control tumor volume and prevent or reverse visual disorders and endocrinopathies. Tumors that cause visual symptoms are treated primarily with transsphenoidal surgery or craniotomy; and if patients are asymptomatic, a wait-and-see approach may be taken. Nonfunctioning PA is not necessarily treated by immediate radiotherapy (RT) after resection, unlike functioning PA. However, several studies have reported recurrences in about 20 -50% of cases treated with surgery alone. 3 -5 Radiotherapy is considered if residual or recurrent tumors invade the cavernous sinus or in cases in which repeated surgeries have resulted in fibrosis and Corresponding Author: Hiromitsu Iwata, MD, PhD, Department of Radiology, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan (h-iwa-ncu@nifty.com). inoperability. In the past, conventional RT was used to treat such cases. 6 -8 Considering the proximity of organs at ri...

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Section: Survival and Local Controlmentioning

confidence: 99%

Section: Survival and Local Controlmentioning

confidence: 99%

Hypofractionated stereotactic radiotherapy with CyberKnife for nonfunctioning pituitary adenoma: high local control with low toxicity

Iwata¹,

Sato²,

Tatewaki³

et al. 2011

Neuro-Oncology

117

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“…The BED 10 was 51.3 Gy for the 27 Gy/3 fr schedule and 56 Gy for the 40 Gy/10 fr schedule. Although the BED must be cautiously used in these dose-fractionation ranges [28,29], it was recommended that an appropriate BED 10 range was 42 to 56 Gy. Therefore, we started with a prescription dose of 28 Gy delivered in 4 fractions, with a BED of 47.6 Gy.…”

Section: Discussionmentioning

confidence: 99%

Treatment of Single or Multiple Brain Metastases by Hypofractionated Stereotactic Radiotherapy Using Helical Tomotherapy

Nagai

Shibamoto

Yoshida

et al. 2014

IJMS

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This study investigated the clinical outcomes of a 4-fraction stereotactic radiotherapy (SRT) study using helical tomotherapy for brain metastases. Between August 2009 and June 2013, 54 patients with a total of 128 brain metastases underwent SRT using tomotherapy. A total dose of 28 or 28.8 Gy at 80% isodose was administered in 4 fractions for all tumors. The mean gross tumor volume (GTV) was 1.9 cc. Local control (LC) rates at 6, 12, and 18 months were 96%, 91%, and 88%, respectively. The 12-month LC rates for tumors with GTV ≤0.25, >0.25 and ≤1, and >1 cc were 98%, 82%, and 93%, respectively; the rates were 92% for tumors >3 cc and 100% for >10 cc. The 6-month rates for freedom from distant brain failure were 57%, 71%, and 55% for patients with 1, 2, and ≥3 brain metastases, respectively. No differences were significant. No major complications were observed. The 4-fraction SRT protocol provided excellent tumor control with minimal toxicity. Distant brain failure was not so frequent, even in patients with multiple tumors. The results of the current study warrant a prospective randomized study comparing single-fraction stereotactic radiosurgery (SRS) with SRT in this patient population.

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“…on one side, and by the use of "hybrid shots" with the new "Perfexion" whenever dealing with crucial targeting (7,36,50,57,58,66). 2. the introduction of dedicated algorhitms accurately "driving" the dose planning system, with probabilistic models including stockastic monitoring, quadrature-sum analysis (20) and linear-quadratic formalisms (32). These techniques, and the concomitant diffusion of phantom studies, have repeatedly confirmed the reliability of such referrals, consistently improving the main conformity indexes.…”

Section: Gamma Knife Radiosurgerymentioning

confidence: 97%

“…dose volume integral, conformity index etc. (6,20,22,56,72,83,86) However, recent reports have emphasized the extremely high chances to maintain adequate LTC rates -without increasing side effects-by treating larger meningiomas with either fractionated schedules or reduced dosages (3,13,18,19,22,24,31,32). b. the controversial or disappointing results obtained in atypic and anaplastic lesions (17,25,27,30,51,73), sometimes characterized by intra-or extraneuraxis metastatization (17) or by enhanced growth after radiosurgery (6,14,42); c. the still pronounced morbidity rate of this technique on sensory nerves (6,14,77).…”

Section: Anaplastic (Gr 3) Meningiomamentioning

confidence: 99%

Radiosurgical Treatment of Intracranial Meningiomas: Update 2011

Gerosa¹,

Foroni²,

Longhi³

et al. 2011

Gamma Knife Radiosurgery

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Estimation of Errors Associated With Use of Linear-Quadratic Formalism for Evaluation of Biologic Equivalence Between Single and Hypofractionated Radiation Doses: An In Vitro Study

Cited by 41 publications

References 32 publications

Hypofractionated stereotactic radiotherapy with CyberKnife for nonfunctioning pituitary adenoma: high local control with low toxicity

Hypofractionated stereotactic radiotherapy with CyberKnife for nonfunctioning pituitary adenoma: high local control with low toxicity

Treatment of Single or Multiple Brain Metastases by Hypofractionated Stereotactic Radiotherapy Using Helical Tomotherapy

Radiosurgical Treatment of Intracranial Meningiomas: Update 2011

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