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Applicability of the Linear-Quadratic Model for Non-Small Cell Lung Cancer Patients Undergoing Stereotactic Body Radiotherapy: A Radiobiological Analysis

BT Huang, JY Lu, WZ Zhang*, Cancer Hospital of Shantou University Medical College, Shantou, Guangdong


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Although the outcome of stereotactic body radiotherapy (SBRT) treatment for early stage lung cancer is encouraging, the applicability of linear quadratic (LQ) model for modeling hypofractionated radiation therapy for lung cancer is widely debated nowadays. The study aims to clarify whether the LQ model is applicable for SBRT treatment for lung cancer by using radiobiological analysis.

Methods: Computer Tomography (CT) simulation data sets for 20 patients diagnosed with stage I primary non-small cell lung cancer (NSCLC) were included in the study. SBRT treatment plans were designed using single fraction of 30 Gy. The transition dose (dT) in the universal survival curve (USC) and modi�ed linear quadratic and linear (mLQL) models were presented. Besides, the biologically effective dose (BED) and the tumor control probability (TCP) values in the USC model were compared with that calculated from the traditional LQ model.

Results: It was found that the dT values in the mLQL model were much higher than that from the USC model. The dT values in the USC model were equal to 29.6 Gy, 33.8 Gy and 44.5 Gy whereas the values were 90.2 Gy, 84.0 Gy and 57.3 Gy in the mLQL mode for 1-year, 2-year and 3-year TCP prediction. Additionally, we also found that the difference of TCP value between the LQ and USC models was less than 3% although the BED values in the two models are significantly different.

Conclusion: Radiobiological analysis reveals that the traditional LQ model is applicable for modeling the SBRT treatment for lung cancer even at extremely high fractional dose.

Funding Support, Disclosures, and Conflict of Interest: This work was sponsored by National Natural Science Foundation of China (81602667) and Medical Scientific Research Foundation of Guangdong Province (A2015534, B2016048).


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