Premium
Coverage‐based treatment planning to accommodate delineation uncertainties in prostate cancer treatment
Author(s) -
Xu Huijun,
Gordon J. James,
Siebers Jeffrey V.
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4928490
Subject(s) - margin (machine learning) , prostate , radiation treatment planning , nuclear medicine , prostate cancer , medicine , dosimetry , percentile , coverage probability , mathematics , radiation therapy , computer science , radiology , statistics , cancer , confidence interval , machine learning
Purpose: To compare two coverage‐based planning (CP) techniques with fixed margin‐based (FM) planning for high‐risk prostate cancer treatments, with the exclusive consideration of the dosimetric impact of delineation uncertainties of target structures and normal tissues. Methods: In this work, 19‐patient data sets were involved. To estimate structure dose for each delineated contour under the influence of interobserver contour variability and CT image quality limitations, 1000 alternative structures were simulated by an average‐surface‐of‐standard‐deviation model, which utilized the patient‐specific information of delineated structure and CT image contrast. An IMRT plan with zero planning‐target‐volume (PTV) margin on the delineated prostate and seminal vesicles [clinical‐target‐volume (CTV prostate ) and CTV SV ] was created and dose degradation due to contour variability was quantified by the dosimetric consequences of 1000 alternative structures. When D 98 failed to achieve a 95% coverage probability objective D 98,95 ≥ 78 Gy (CTV prostate ) or D 98,95 ≥ 66 Gy (CTV SV ), replanning was performed using three planning techniques: (1) FM (PTV prostate margin = 4,5,6 mm and PTV SV margin = 4,5,7 mm for RL, PA, and SI directions, respectively), (2) CP OM which optimized uniform PTV margins for CTV prostate and CTV SV to meet the D 98,95 objectives, and (3) CP COP which directly optimized coverage‐based objectives for all the structures. These plans were intercompared by computing percentile dose‐volume histograms and tumor‐control probability/normal tissue complication probability (TCP/NTCP) distributions. Results: Inherent contour variability resulted in unacceptable CTV coverage for the zero‐PTV‐margin plans for all patients. For plans designed to accommodate contour variability, 18/19 CP plans were most favored by achieving desirable D 98,95 and TCP/NTCP values. The average improvement of probability of complication free control was 9.3% for CP COP plans and 3.4% for CP OM plans. Conclusions: When the delineation uncertainties need to be considered for prostate patients, CP techniques can produce more desirable plans than FM plans for most patients. The relative advantages between CP COP and CP OM techniques are patient specific.