has been investigated within the framework of the linear—quadratic model. 4 The fraction S of cells surviving an instantaneous radiation of dose d (Gy) in the linear—quadratic model is: where BED = d [1 + d/(α/β)] and is known as the biologically effective dose. For extended treatments, the BED is the value (Gy) in the cell-survival equation, which would result in the same surviving fraction as the actual treatment. For a pair of gamma knife treatment Sessions A and B, the cumulative BED is: where d A and d B are doses delivered during Sessions A
Jonathan P. Knisely, James E. Bond, Ning J. Yue, Colin Studholme and Alain C. J. de Lotbinière
Benjamin H. Kann, James B. Yu, John M. Stahl, James E. Bond, Christopher Loiselle, Veronica L. Chiang, Ranjit S. Bindra, Jason L. Gerrard and David J. Carlson
, it is of utmost importance to investigate factors that may contribute to treatment-related adverse effects in GKRS. Although there have been studies supporting an association of functional GKRS parameters such as prescription dose, target location, and treatment volume with toxicity, 20 , 24 the impact of the age of the cobalt-60 source has been seldom studied. Cobalt-60 source age directly correlates with dose rate and treatment time, factors that may independently influence the biologically effective dose (BED) of treatment depending on the propensity for the
Constantin Tuleasca, Iulia Peciu-Florianu, Henri-Arthur Leroy, Maximilien Vermandel, Mohamed Faouzi and Nicolas Reyns
microsurgical resection, 6–8 endovascular treatment, 9 and stereotactic radiosurgery (SRS) 10 , 11 used alone or in the frame of a multidisciplinary approach. 12–14 In the present study, we investigated the role of the biologically effective dose (BED) on the outcomes after upfront SRS by Gamma Knife radiosurgery (GKRS) for unruptured AVMs. Of note, BED reflects the biological effectiveness of the total physical dose applied during a certain time. 15 Unlike the radiation dose, BED integrates a time factor correction, accounting for DNA repair. Previously, the particular
Jinyu Xue, Gregory J. Kubicek, Jimm Grimm, Tamara LaCouture, Yan Chen, H. Warren Goldman and Ellen Yorke
effective doses (BEDs) for both treatment targets and for the normal CNS tissues in patients with > 10 brain metastases. We used 5 representative cases to demonstrate the fundamental differences in dosimetric and biological outcomes between SRS and WBRT. Some issues related to the normal tissue complications induced by radiation dose-volume effects are raised and are discussed in the context of the current knowledge of the efficacy and safety of the 2 treatment modalities. Methods This study was approved by the Cooper Health System Internal Review Board. We examined the
Evangelia Katsoulakis, Nadeem Riaz, Brett Cox, James Mechalakos, Joan Zatcky, Mark Bilsky and Yoshiya Yamada
The objective of this study was to investigate the feasibility and safety of delivering a third course of radiation to patients with multiply recurrent metastatic disease to the spine.
Between 2009 and 2011, 10 patients received a third course of radiation to spinal metastases at Memorial Sloan–Kettering Cancer Center using image-guided intensity-modulated radiation therapy (IMRT). Patient and tumor characteristics, dosimetry details, and outcomes were obtained using retrospective chart review. Spinal imaging was performed prior to treatment and at regular follow-up intervals. The cumulative biologically effective dose (BED) to the spinal cord and cauda equina was calculated and was normalized to 2 Gy equivalents (Gy2/2). Toxicity and local control were assessed.
The median time between the first and second courses of radiation was 18.5 months and the median time between the second and third courses was 11.5 months. The median follow-up from the third course of radiation was 12 months and the median overall survival was 13 months. Pain or neurological symptoms were improved in 80% of patients. The median spinal cord maximum dose normalized BED (nBED) for the whole cohort was 70.73 Gy2/2 (range 51.9–101.7 Gy2/2). The median dose to 5% of the spinal cord D05 nBED for the entire cohort was 59.4 Gy2/2. Acute toxicity was most commonly fatigue and dermatitis, with 1 patient experiencing Grade 3 fatigue and 1 patient Grade 3 dermatitis. Late toxicity was limited to 2 cases of Grade 1 dysphagia. There was 1 case of Grade 1 neuropathy and 1 case of Grade 2 neuropathy. The crude rate of local control was 80% with 1 in-field failure and 1 marginal failure.
In this cohort of patients, a third course of IMRT to the spine was well tolerated with no significant late toxicities. Used as salvage therapy for select patients, a third course of radiation is a safe and effective treatment strategy.
Iuliana Toma-Dasu, Helena Sandström, Pierre Barsoum and Alexandru Dasu
following oxic parameters were assumed for calculation 17 : α = 0.35 Gy −1 and α/β = 10 Gy. Fractionated schedules with 3, 4, and 5 fractions leading to the same biological effective doses (BEDs) to the tumor 3 (i.e., for α/β = 10 Gy) were also considered for the larger target ( Table 2 ). In this case, TCP was calculated assuming that fast local reoxygenation takes place between fractions. TABLE 2: Fractionated schedules with 3, 4, and 5 fractions leading to the same BEDs to the tumor, BED 10 , as 18 Gy delivered in a single fraction, and the corresponding BED to
Shannon Fogh, Lijun Ma, Nalin Gupta, Arjun Sahgal, Jean L. Nakamura, Igor Barani, Penny K. Sneed, Michael McDermott and David A. Larson
minus the target volume, in biological equivalence to the corresponding volume-staged Gamma Knife treatment plan. For the purpose of illustration, suppose that a composite volume receiving 12 Gy in a volume-staged Gamma Knife treatment plan was found to equal 15.0 cm 3 , then when setting the target dose for an n-fraction SRT treatment, we would first adjust the prescribed dose value such that the plan produced exactly 15 cm 3 of 12 Gy according to the biologically effective dose. In the context of the standard linear quadratic model, this means that 15 cm 3 of the
Dennis T. Lockney, Angela Y. Jia, Eric Lis, Natalie A. Lockney, Chengbao Liu, Benjamin Hopkins, Daniel S. Higginson, Yoshiya Yamada, Ilya Laufer, Mark Bilsky and Adam M. Schmitt
S tereotactic body radiation therapy (SBRT) has emerged as a highly effective treatment modality for obtaining durable local control of a variety of primary cancers, including early-stage lung cancer and metastatic lesions in both bone and soft tissues. The delivery of a high biologically effective dose (BED) by administering large radiation doses in a few fractions is especially attractive for the treatment of tumors with a radioresistant histology and also for tumors that have been previously irradiated. However, when treating spinal tumors, ensuring dose
Ahmad Alhourani, Zaid Aljuboori, Mehran Yusuf, Shiao Y. Woo, Eyas M. Hattab, Norberto Andaluz and Brian J. Williams
locations only after 2009, and does not provide Simpson grading. Therefore, the cohorts were solely stratified by adjuvant RT treatment. We calculated the biologically effective dose (BED) from the total dose and fractionation scheme by using an α/β ratio of 3.7 Gy to standardize dosing across patients. 22 Statistical Analysis Statistical analyses were conducted using MATLAB version 9.3 (The MathWorks, Inc.). Univariate differences were assessed using chi-square tests for categorical covariates and ANOVA for numerical covariates. For trends analysis, a linear regression
Jonathan E. Leeman, Mark Bilsky, Ilya Laufer, Michael R. Folkert, Neil K. Taunk, Joseph R. Osborne, Julio Arevalo-Perez, Joan Zatcky, Kaled M. Alektiar, Yoshiya Yamada and Daniel E. Spratt
. These values were used to formulate a recurrence mapping of failures within the spine with respect to the treated vertebral level(s). For the purposes of this analysis, all sacral lesions were considered to be the same level. For univariate and multivariate analyses, histology was dichotomized by chondrosarcoma and fibrosarcoma versus other histological type. Tumor location was dichotomized by lumbar versus all other locations. The SBRT dose was analyzed as biologically effective dose and was dichotomized to 216 versus < 216 (i.e., 2400 cGy in a single fraction vs