Radiobiological model-based bio-anatomical quality assurance in intensity-modulated radiation therapy for prostate cancer - Abstract

A bio-anatomical quality assurance (QA) method employing tumor control probability (TCP) and normal tissue complication probability (NTCP) is described that can integrate radiobiological effects into intensity-modulated radiation therapy (IMRT).

We evaluated the variations in the radiobiological effects caused by random errors (r-errors) and systematic errors (s-errors) by evaluating TCP and NTCP in two groups: patients with an intact prostate (Gintact) and those who have undergone prostatectomy (Gtectomy). The r-errors were generated using an isocenter shift of ±1 mm to simulate a misaligned patient set-up. The s-errors were generated using individual leaves that were displaced inwardly and outwardly by 1 mm on multileaf collimator field files. Subvolume-based TCP and NTCP were visualized on computed tomography (CT) images to determine the radiobiological effects on the principal structures. The bio-anatomical QA using the TCP and NTCP maps differentiated the critical radiobiological effects on specific volumes, particularly at the anterior rectal walls and planning target volumes. The s-errors showed a TCP variation of -40-25% in Gtectomy and -30-10% in Gintact, while the r-errors were less than 1.5% in both groups. The r-errors for the rectum and bladder showed higher NTCP variations at ±20% and ±10%, respectively, and the s-errors were greater than ±65% for both. This bio-anatomical method, as a patient-specific IMRT QA, can provide distinct indications of clinically significant radiobiological effects beyond the minimization of probable physical dose errors in phantoms.

Written by:
Park JY, Lee JW, Chung JB, Choi KS, Kim YL, Park BM, Kim Y, Kim J, Choi J, Kim JS, Hong S, Suh TS.   Are you the author?
Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.

Reference: J Radiat Res. 2012 Aug 21. Epub ahead of print.
doi: 10.1093/jrr/rrs049

PubMed Abstract
PMID: 22915778 Prostate Cancer Section