Target Volume Heterogeneity Index, a Potentially Valuable Metric in IMRT Prostate Cancer Treatment PlanningMichael M. Dominello1*, Isaac Kaufman2, Erin McSpadden2, Michael Snyder3, Mark Zaki2, Jordan Maier2, Peter Paximadis2 and Steven Miller2
- *Corresponding Author:
- Michael M. Dominello
DO, Department of Radiation Oncology
Wayne State, niversity School of Medicine
Barbara Ann Karmanos Cancer Center, 4100 John R
Mailcode GE00RO Detroit, MI 48201, USA
Tel: 313 576-9622
Fax: 313 576-9625
E-mail: [email protected]
Received date: July 29, 2014; Accepted date: September 30, 2014; Published date: October 07, 2014
Citation: Dominello MM, Kaufman I, McSpadden E, McSpadden M, Zaki M, et al. (2014) Target Volume Heterogeneity Index, a Potentially Valuable Metric in IMRT Prostate Cancer Treatment Planning. J Nucl Med Radiat Ther 5:192. doi: 10.4172/2155-9619.1000192
Copyright: © 2014 Dominello MM, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Purpose/Objectives: Heterogeneity index (HI) has been described in the literature as a tool for evaluating dose gradients within a planning target volume (PTV). HI may be expressed as D1/D95 where D1 and D95 equal the dose encompassing 1% and 95% of the target volume. The purpose of this study is to evaluate the effect of target volume dose heterogeneity on dose received by local organs at risk in the treatment of low and intermediate risk prostate cancer.
Materials/Methods: Treatment plans were reviewed for 157 patients with low or intermediate risk prostate cancer treated with dose-escalated radiation therapy between 6/2007 and 2/2012. Patients treated in the post-operative setting or receiving pelvic nodal irradiation were excluded. Patients were treated with either standard intensity modulation (IMRT) using 7 or 8 fields or 2-arc volumetric modulated arc therapy (VMAT). All patients had daily image-guidance. PTV HI (D1/D95) and dose-volume histogram (DVH) data at 8 dose levels for rectum and bladder were recorded. Patients were categorized into two groups (low HI or high HI) with respect to median index score. A two-tailed t-test was used to test for differences in dose received by rectum and bladder for the two groups.
Results: For the 157 plans evaluated, mean PTV volume was 164cc and mean prescription dose was 7833cGy. Median HI was 1.04 (range 1.0-1.08). Low HI (≤1.04) was found to correlate with significantly lower rectal V50 (p=0.02), V55 (p=0.01), V60 (p=0.01), V65 (p=0.01), and V70 (p=0.01). There was no significant correlation with dose received by bladder at any dose level. HI was similar for patients treated with standard IMRT and VMAT (p=0.85).
Conclusions: Target volume HI ≤1.04 is associated with more favorable rectal doses at clinically relevant dose-levels. We believe HI may serve as a valuable metric in prostate cancer treatment planning. Further work is needed to correlate these dosimetric findings with clinical outcomes.