Real-time image-guided adaptive-predictive prostate radiotherapy using rectal diameter as a predictor of motion

Oates, R., Brown, A., Tan, A., Foroudi, F., Joon, M. Lim, Schneider, M., Herschtal, A., and Kron, T. (2017) Real-time image-guided adaptive-predictive prostate radiotherapy using rectal diameter as a predictor of motion. Clinical Oncology, 29 (3). pp. 180-187.

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Abstract

Aims: To investigate a relationship between maximum rectal diameter (MRD) on pre-treatment cone beam computed tomography (CBCT) and intra-fraction prostate motion, in the context of an adaptive image-guided radiotherapy (IGRT) method.

Materials and methods: The MRD was measured on 2125 CBCTs from 55 retrospective patient datasets and related to prostate displacement from intra-fraction imaging. A linear regression model was developed to determine a threshold MRD associated with a high probability of small prostate displacement. Standard and reduced adaptive margin plans were created to compare rectum and bladder normal tissue complication probability (NTCP) with each method.

Results: A per-protocol analysis carried out on 1910 fractions from 51 patients showed with 90% confidence that for a MRD <= 3 cm, prostate displacement will be <= 5 mm and that for a MRD <= 3.5 cm, prostate displacement will be <= 5.5 mm. In the first scenario, if adaptive therapy was used instead of standard therapy, median reductions in NTCP for rectum and bladder were 0.5% (from 9.5% to 9%) and 1.3% (from 6.6% to 5.3%), respectively. In the second scenario, the NTCP for rectum and bladder would have median reductions of 1.1% and 2.6%, respectively.

Conclusions: We have identified a potential method for adaptive prostate IGRT based upon predicting small prostate intra-fraction motion by measuring MRD on pre-treatment CBCT.

Item ID: 50506
Item Type: Article (Research - C1)
ISSN: 1433-2981
Keywords: adaptive, IGRT, NTCP, prostate cancer, radiotherapy
Funders: Peter MacCallum Centre, Townsville Cancer Centre
Date Deposited: 20 Sep 2017 09:42
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1112 Oncology and Carcinogenesis > 111204 Cancer Therapy (excl Chemotherapy and Radiation Therapy) @ 100%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920102 Cancer and Related Disorders @ 100%
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