Radiobiological effectiveness and its role in modelling secondary cancer risk for proton therapy

Conference Paper

Madkhali, A . 2016

• نوع عمل المنشور: Poster
• الوسوم: RBE, radiotherapy, secondary cancer risk
• اسم المؤتمر: 55th Annual Conference of the Particle Therapy Co-operative Group
• عنوان المؤتمر: Prague, Czech Republic
• تاريخ المؤتمر: الأحد, آيار (مايو) 22, 2016
• المنظمة الراعية: Particle Therapy Co-operative Group

مستخلص المنشور

Background:
In proton therapy, a radiobiological effectiveness ratio (RBE) of 1.1 (RBE1.1) is often used. In reality, RBE depends on dose, linear energy transfer (LET), biological end point, and tissue type. Using a value of RBE that may be not accurate may affect dose calculation and hence, outcome.
 
 
Method(s):
We used an in-house built code for modelling malignant induction probability (MIP) from voxel-by-voxel dose map (Timlin 2014) and implement a published model to calculate structure-specific RBE, recalculate dose and MIP, and compare the outcomes with initial calculations using RBE1.1. MIP was calculated using linear quadratic (LQ), linear (LIN), and linear-no-threshold (LNT) models for proton therapy plans for an adult and a teenage patient diagnosed with medulloblastoma (MB). The MIP was then re-calculated using the RBE model  which is a function of dose (d), α and β and RBEmin and RBEmax.

 
 
Results:
Results are shown in Table 1. The difference in MIP by using RBE1.1 and RBEMinMax  is ~2-3%. The effect on mean dose varies between different organs and is between 6% and 8%. Clinical implications due to difference in RBE depend on beam characteristics, dose, structures concerned, and the volume irradiated.
 
 
Conclusions:
Using RBE1.1 makes proton therapy dose and dose-dependent predictions less accurate. Our results using a RBE calculation model show that decreased accuracy may have clinical implications, which agrees with published literature (Jones 2012;  Jones, 2014), and may affect secondary cancer risk and normal tissue complication probability calculations as well.