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Investigative Study of a Hybrid Dose Response Relationship to Predict High Dose Fractionation Response in the Lung Cancer Stereotactic Body Radiation Therapy Using Lung Cancer Cell Lines

T Kehwar

T. S. Kehwar1*, K. L. Chopra2, D. V. Rai2, (1)Department of Radiation Oncology, Eastern Virginia Medical School, Sentara Obici Hospital, Suffolk, VA 23434. (2)Department of Biomedical Engineering, Shobhit University, Gangoh, UP, India.


SU-I-GPD-T-521 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: This study is designed to investigates a hybrid model to predict the effect of SBRT in lung cancers.

Methods: Survival data of 22 cell lines digitized from charts of published reports to determine α, β, D0 and n (extrapolation number) by fitting exp(-αD)to initial data and to exponential region. The values of α, β, D0 and n of 35 cell lines were also extracted from report to determine representative parameters(RP). The LQ, LQ-L and USC models were plotted for transition dose Dt(derived from MT model) calculated using α, β, D0 and n, and Dt=2α/β, for each cell lines, and RP to investigate approximation of the issue pertained in SBRT.

Results: The mean α, β, D0 and n were found to be 0.46±0.23Gy-1, 0.08±0.04Gy-2, 1.04±0.29Gy, and 3.97±3.63, respectively, for SC cell lines, and 0.33±0.21Gy-1, 0.04±0.02 Gy-2, 1.25±0.21Gy, and 4.88±2.39, respectively, for NSC cell lines. RP α, β, D0 and n, were 0.47Gy-1, 0.07Gy-2, 1.05Gy, and 3.89, respectively, for SC, and 0.30Gy-1, 0.05Gy-2, 1.19Gy, and 5.59, respectively, for NSC cell lines. The LQ-L plots, using Dt, proved its validity over LQ and USC models, for SC and NSC cell lines.

Conclusion: The LQ-L curves, with Dt, provide best fit with smooth and gradual transition to linear portion of the curve at Dt, where LQ curve loses its validity, while USC curve does not transition smoothly to linear portion, which validates that LQ-L model, with Dt, is able to fit wide variety of survival data over the range of high dose fraction used in SBRT, for SC and NSC cell lines. The LQ-L model, with Dt, retains all strength of the LQ model in the low-dose range, provides useful clinical tool to compare and analyze high dose fractions used in SBRT for lung cases.

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