Applicability of the linear-quadratic formalism for modeling local tumor control probability in high dose per fraction stereotactic body radiotherapy for early stage non-small cell lung cancer

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• 作者：Matthias Guckenberger ; Rainer Johannes Klement ; Michael Allg盲uer ; Steffen Appold ; Karin Dieckmann ; Iris Ernst ; Ute Ganswindt ; Richard Holy ; Ursula Nestle ; Meinhard Nevinny-Stickel ; Sabine Semrau ; Florian Sterzing ; Andrea Wittig ; Nicolaus Andratschke ; Michael Flentje
• 关键词：Stereotactic body radiotherapy ; Non-small cell lung cancer ; Dose&ndash ; response modeling ; Linear-quadratic formalism ; Biologically effective dose
• 刊名：Radiotherapy and Oncology
• 出版年：October, 2013
• 年：2013
• 卷：109
• 期：1
• 页码：13-20
• 全文大小：597 K

文摘

Background and purpose

To compare the linear-quadratic (LQ) and the LQ-L formalism (linear cell survival curve beyond a threshold dose d_T) for modeling local tumor control probability (TCP) in stereotactic body radiotherapy (SBRT) for stage I non-small cell lung cancer (NSCLC).

Materials and methods

This study is based on 395 patients from 13 German and Austrian centers treated with SBRT for stage I NSCLC. The median number of SBRT fractions was 3 (range 1-8) and median single fraction dose was 12.5 Gy (2.9-33 Gy); dose was prescribed to the median 65% PTV encompassing isodose (60-100%). Assuming an 伪/尾-value of 10 Gy, we modeled TCP as a sigmoid-shaped function of the biologically effective dose (BED). Models were compared using maximum likelihood ratio tests as well as Bayes factors (BFs).

Results

There was strong evidence for a dose-response relationship in the total patient cohort (BFs > 20), which was lacking in single-fraction SBRT (BFs < 3). Using the PTV encompassing dose or maximum (isocentric) dose, our data indicated a LQ-L transition dose (d_T) at 11 Gy (68% CI 8-14 Gy) or 22 Gy (14-42 Gy), respectively. However, the fit of the LQ-L models was not significantly better than a fit without the d_T parameter (p = 0.07, BF = 2.1 and p = 0.86, BF = 0.8, respectively). Generally, isocentric doses resulted in much better dose-response relationships than PTV encompassing doses (BFs > 20).

Conclusion

Our data suggest accurate modeling of local tumor control in fractionated SBRT for stage I NSCLC with the traditional LQ formalism.