Sensitivity Analysis of Parameters in Linear-Quadratic Radiobiologic Modeling

Radiosurgical Treatment of Intracranial Meningiomas: Update 2011

“…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.…”

“…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).…”

Individualized higher dose of 70–75 Gy using five-fraction robotic stereotactic radiotherapy for non-small-cell lung cancer: A feasibility study

“…Such high doses may be needed to achieve local tumor control based on the hypothesis that, if radio-resistant hypoxic cells are present, or some cells are in a resistant phase of the cell cycle, then doses two-anda-half to three times as great as those required to kill well-oxygenated cells are required to kill this cell population. A total dose of 75 Gy to 85 Gy would then offer a chance of reducing the tumor burden for a 1-to 10 -g tumor to one viable cell on average [17,18,33]. If reoxygenation is incomplete, and only 1% of tumor cells remain hypoxic, then doses many orders of magnitude higher would be required to kill these cells.…”

“…Here we present the results of a higher dose using CyberKnife hypofractionation delivered in five fractions, designed to test the feasibility of increasing the total dose up to 75 Gy, taking advantage of the high / ratio of NSCLC (which could be as high as 50 Gy), which should result in an increase in cell kill by 10%, reduce late complications by more than 10%, and thereby improve the therapeutic ratio, local control, and survival [17,18].…”

Radiobiology of Radioresistant Glioblastoma

“…Results from the huge empirical data base obtained in the clinic for the relative effect of different doses and protocols that induced both tumor regression and normal tissue toxicity, clearly demonstrated radiotherapy of some tumors was more successful when multiple doses below 3 Gy were used. Mathematical models were proposed to explain the rate of inactivation of tumors at lower doses circa 1 to 3 Gy and the most successful model was the "linear-quadratic (LQ) model" as proposed by Hendry ( 16) and by Fowler ( 17,18). The LQ model was based on the concept that tumor cell inactivation was induced at a linear rate at lower doses (the alpha response) but reflected a quadratic component at higher doses determined by a coefficient beta times the square of the dose (the beta response).…”