The linear-quadratic model is inappropriate to model high dose per fraction effects in radiosurgery

2009 ◽  
Vol 36 (8) ◽  
pp. 3381-3384 ◽  
Author(s):  
John P. Kirkpatrick ◽  
David J. Brenner ◽  
Colin G. Orton
Keyword(s):  
Quadratic Model ◽  
High Dose ◽  
Linear Quadratic ◽  
Linear Quadratic Model ◽  
Dose Per Fraction

PO-0941 INADEQUACY OF USING THE LINEAR-QUADRATIC MODEL IN HIGH-DOSE-PER-FRACTION RADIOTHERAPY: IN VITRO AND IN VIVO STUDY

2012 ◽  
Vol 103 ◽  
pp. S371
Author(s):  
Y. Shibamoto ◽  
S. Otsuka ◽  
H. Iwata ◽  
A. Miyakawa ◽  
C. Sugie ◽  
...  
Keyword(s):  
In Vivo Study ◽  
Quadratic Model ◽  
High Dose ◽  
Linear Quadratic ◽  
Linear Quadratic Model ◽  
Dose Per Fraction

scholarly journals Clinical comparison of toxicity pattern of two linear quadratic model-baesd fractionation schemes of high-dose-rate intracavitary brachytherapy for cervical cancer

2016 ◽  
Author(s):  
Ankit Batra
Keyword(s):  
Cervical Cancer ◽  
Dose Rate ◽  
High Dose Rate ◽  
Sub Saharan Africa ◽  
Quadratic Model ◽  
Intracavitary Brachytherapy ◽  
High Dose ◽  
Linear Quadratic ◽  
Carcinoma Cervix ◽  
Linear Quadratic Model

Introduction: Carcinoma cervix is the fourth (GLOBACON 2012) most common cancer among women worldwide, and the main cancer affecting women in Sub-Saharan Africa, Central America and south-central Asia. In India, approx. 1,23,000 (GLOBACON 2012) new cases of carcinoma cervix are diagnosed each year. Brachytherapy is an integral part of treatment of cancer cervix. In the context of a developing country like us where maximum utilization of the resource is of prime importance to provide treatment to the large patient cohort, shortening the treatment duration and number of fractions always increases efficiency. In order to maximize the logistic benefits of HDR-BT while improving patient compliance and resource sparing, various fractionation regimens are used. Fractionation and dose adjustments of the total dose are radiobiologically important factors in lowering the incidence of complications without compromising the treatment results. Aim: To compare patient outcomes and complications using two linear-quadratic model-based fractionation schemes of high-dose-rate intracavitary brachytherapy (HDR-IC) used to treat cervical cancer. Materials and Methods: A prospective randomized study on 318 patients, with histologically proven advanced carcinoma cervix (stages IIB-IIIB) was enrolled in the study. All patients received External Beam Radio Therapy (EBRT) 50 Gy in 25 fractions with concurrent chemotherapy (cisplatin 35 mg/m2) followed by IntraCavitary brachytherapy using high dose rate equipment. Patients were randomised after completion of EBRT into two arms: (1) Arm 1: HDR ICRT 6.5 Gy per fraction for 3 fractions, a week apart. (2) Arm 2: HDR ICRT, 9 Gy per fraction for 2 fractions, 1 week apart. On completion of treatment, patients were assessed monthly for 3 months followed by 3 monthly thereafter. Treatment response was assessed according to WHO criteria after one month of completion of radiotherapy. The RTOG criteria were used for radiation induced toxicities. We analyzed late toxicities in terms of Rectal, Bladder, Small Bowel toxicity and Vaginal Stenosis. Results: Acute reactions in both the groups were comparable. None of the patient developed Grade 4 toxicity in our study and no toxicity related mortality was encountered. A slightly high frequency of late toxicity was observed in 9Gy Arm patients but was not statistically significant. Conclusion: In our setup, HDR brachytherapy at 9 Gy per fraction in two fractions is safe, effective and resource saving method with good local control, survival, and manageable normal tissue toxicity.

scholarly journals Analytical solution to the radiotherapy fractionation problem including dose bound constraints

2021 ◽  
Author(s):  
Luis Alberto Fernández ◽  
Lucía Fernández
Keyword(s):  
At Risk ◽  
Radiation Effect ◽  
Organs At Risk ◽  
Dose Fractionation ◽  
Quadratic Model ◽  
High Dose ◽  
Bound Constraints ◽  
Linear Quadratic ◽  
Linear Quadratic Model ◽  
Radiotherapy Dose

Abstract This paper deals with the classic radiotherapy dose fractionation problem for cancer tumors concerning the following goals: a) To maximize the effect of radiation on the tumor, restricting the effect produced to the organs at risk (healing approach). b) To minimize the effect of radiation on the organs at risk, while maintaining enough effect of radiation on the tumor (palliative approach). We will assume the linear-quadratic model to characterize the radiation effect and consider the stationary case (that is, without taking into account the timing of doses and the tumor growth between them). The main novelty with respect to previous works concerns the presence of minimum and maximum dose fractions, to achieve the minimum effect and to avoid undesirable side effects, respectively. We have characterized in which situations is more convenient the hypofractionated protocol (deliver few fractions with high dose per fraction) and in which ones the hyperfractionated regimen (deliver a large number of lower doses of radiation) is the optimal strategy. In all cases, analytical solutions to the problem are obtained in terms of the data. In addition, the calculations to implement these solutions are elementary and can be carried out using a pocket calculator.

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