Adaptive fractionation therapy: I. Basic concept and strategy

Radiotherapy is fractionized to increase the therapeutic ratio. Fractionation in conventional treatment is determined as part of the prescription, and a fixed fraction size is used for the whole course of treatment. Due to patients' day-to-day variations on the relative distance between the tumor and the organs at risk (OAR), a better therapeutic ratio may be attained by using an adaptive fraction size. Intuitively, we want to use a larger fraction size when OAR and the tumor are far apart and a smaller fraction size when OAR and the tumor are close to each other. The concept and strategies of adaptive fractionation therapy (AFT) are introduced in this paper. AFT is an on-line adaptive technique that utilizes the variations of internal structures to get optimal OAR sparing. Changes of internal structures are classified as different configurations according to their feasibility to the radiation delivery. A priori knowledge is used to describe the probability distribution of these configurations. On-line processes include identifying the configuration via daily image guidance and optimizing the current fraction size. The optimization is modeled as a dynamic linear programming problem so that at the end of the treatment course, the tumor receives the same planned dose while OAR receives less dose than the regular fractionation delivery. Extensive simulations, which include thousands of treatment courses with each course consisting of 40 fractions, are used to test the efficiency and robustness of the presented technique. The gains of OAR sparing depend on the variations on configurations and the bounds of the fraction size. The larger the variations and the looser the bounds are, the larger the gains will be. Compared to the conventional fractionation technique with 2 Gy/fraction in 40 fractions, for a 20% variation on tumor-OAR configurations and [1 Gy, 3 Gy] fraction size bounds, the cumulative OAR dose with adaptive fractionation is 3-8 Gy, or 7-20% less than that of the regular fractionation, while maintaining the same cumulative tumor dose as prescribed.

[1]  L. Lajtha,et al.  Rationalisation of fractionation in radiotherapy. , 1960, The British journal of radiology.

[2]  Fractionation in radiotherapy (review). , 1983, Anticancer research.

[3]  D. Shrieve,et al.  Optimal fractionation schedules in small field radiotherapy. , 1994, International journal of radiation oncology, biology, physics.

[4]  D. Yan,et al.  Adaptive radiation therapy , 1997, Physics in medicine and biology.

[5]  Jacques Bernier,et al.  Accelerated fractionation (AF) compared to conventional fractionation (CF) improves loco-regional control in the radiotherapy of advanced head and neck cancers: results of the EORTC 22851 randomized trial. , 1997, Radiotherapy and Oncology.

[6]  J Wong,et al.  Adaptive modification of treatment planning to minimize the deleterious effects of treatment setup errors. , 1997, International journal of radiation oncology, biology, physics.

[7]  J. Horiot,et al.  Accelerated fractionation (AF) compared to conventional fractionation (CF) improves loco-regional control in the radiotherapy of advanced head and neck cancers: results of the EORTC 22851 randomized trial. , 1997, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[8]  N. Burnet,et al.  Altered radiotherapy fractionation: an opportunity not to be missed. , 1998, Clinical oncology (Royal College of Radiologists (Great Britain)).

[9]  D. Yan,et al.  Organ/patient geometric variation in external beam radiotherapy and its effects. , 2001, Medical physics.

[10]  R. Jeraj,et al.  Re-optimization in adaptive radiotherapy. , 2002, Physics in medicine and biology.

[11]  J. Fowler,et al.  Image guidance for precise conformal radiotherapy. , 2003, International journal of radiation oncology, biology, physics.

[12]  Using daily MVCT images to calculate daily rectal dose volume histograms in prostate cancer patients treated with a helical tomotherapy unit , 2004 .

[13]  T. Mackie,et al.  Fast free-form deformable registration via calculus of variations , 2004, Physics in medicine and biology.

[14]  D. Yan,et al.  Computed tomography guided management of interfractional patient variation. , 2005, Seminars in radiation oncology.

[15]  L. Xing,et al.  Optimization of radiotherapy dose-time fractionation with consideration of tumor specific biology. , 2005, Medical physics.

[16]  2795 : Use of Daily CT-Based Deformable Registration To Track Lung Daily Tumor Volumes and Position , 2006 .

[17]  Weiguo Lu,et al.  Deformable registration of the planning image (kVCT) and the daily images (MVCT) for adaptive radiation therapy , 2006, Physics in medicine and biology.

[18]  Quan Chen,et al.  Automatic re-contouring in 4D radiotherapy , 2006, Physics in medicine and biology.

[19]  Dynamic Modulation of Radiotherapy Fractionation: A Simulation Study , 2007 .

[20]  Mingli Chen,et al.  Adaptive fractionation therapy: II. Biological effective dose. , 2008, Physics in medicine and biology.

[21]  SU‐GG‐T‐59: Adaptive Fractionation Therapy — II Biological Effective Dose , 2008 .