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Improvement of therapeutic index for brain tumors with daily image guidance.

Shields LB, Coons JM, Dedich C, Ragains M, Scalf K, Vitaz TW, Spalding AC - Radiat Oncol (2013)

Bottom Line: No reductions to targets occurred with individualized PTVs.Daily imaging allows application of individualized CTV expansion to reduce dose to OAR responsible for neurocognition, learning, and neuroendocrine function below doses shown to correlate with long-term morbidity.The demonstrated reduction in dose to OAR in this study has implications for quality of life and provides the motivation to pursue custom PTV expansion.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Brain Tumor Center, Norton Healthcare, Louisville, KY, USA. acspalding1@gmail.com.

ABSTRACT

Background: Image-guidance maximizes the therapeutic index of brain irradiation by decreasing setup uncertainty. As dose-volume data emerge defining the tolerance of critical normal structures responsible for neuroendocrine function and neurocognition, minimizing clinical target volume (CTV) to planning target volume (PTV) expansion of targets near these structures potentially lessens long-term toxicity.

Methods: We reviewed the treatment records of 29 patients with brain tumors, with a total of 517 fractions analyzed. The CTV was uniformly expanded by 3 mm to create the PTV for all cases. We determined the effect of patient specific factors (prescribed medications, weight gain, tumor location) and image-guidance technique on setup uncertainty and plotted the mean +/- standard deviation for each factor. ANOVA was used to determine significance between these factors on setup uncertainty. We determined the impact of applying the initial three fraction variation as custom PTV-expansion on dose to normal structures.

Results: The initial 3 mm margin encompassed 88% of all measured shifts from daily imaging for all fractions. There was no difference (p = n.s.) in average setup uncertainty between CBCT or kV imaging for all patients. Vertical, lateral, longitudinal, and 3D shifts were similar (p = n.s.) between days 1, 2, and 3 imaging and later fractions. Patients prescribed sedatives experienced increased setup uncertainty (p < 0.05), while weight gain, corticosteroid administration, and anti-seizure medication did not associate with increased setup uncertainty. Patients with targets near OAR with individualized margins led to decreased OAR dose. No reductions to targets occurred with individualized PTVs.

Conclusions: Daily imaging allows application of individualized CTV expansion to reduce dose to OAR responsible for neurocognition, learning, and neuroendocrine function below doses shown to correlate with long-term morbidity. The demonstrated reduction in dose to OAR in this study has implications for quality of life and provides the motivation to pursue custom PTV expansion.

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Related in: MedlinePlus

Initial three IGRT fractions predict future patient position with CBCT. The vertical, lateral, longitudinal, and total three dimensional setup uncertainty averages were plotted with +/- standard deviations for the first three days of treatment in black and all subsequent treatments in white. Student’s t-test was used to determine significance between groups.
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Figure 1: Initial three IGRT fractions predict future patient position with CBCT. The vertical, lateral, longitudinal, and total three dimensional setup uncertainty averages were plotted with +/- standard deviations for the first three days of treatment in black and all subsequent treatments in white. Student’s t-test was used to determine significance between groups.

Mentions: We next determined whether the first three days of IGRT would predict patient setup for subsequent fractions. Patients underwent CBCT for the first three fractions and remarked before the fourth fraction. As shown in Figure 1, there was no statistical difference (p = NS) in setup uncertainty between the first three days of treatment and all subsequent treatments via CBCT image guidance. We also analyzed post treatment images to quantify intrafraction motion. For 100 fractions, the mean difference from pre-treatment to post-treatment images was 0.7 mm.


Improvement of therapeutic index for brain tumors with daily image guidance.

Shields LB, Coons JM, Dedich C, Ragains M, Scalf K, Vitaz TW, Spalding AC - Radiat Oncol (2013)

Initial three IGRT fractions predict future patient position with CBCT. The vertical, lateral, longitudinal, and total three dimensional setup uncertainty averages were plotted with +/- standard deviations for the first three days of treatment in black and all subsequent treatments in white. Student’s t-test was used to determine significance between groups.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4222040&req=5

Figure 1: Initial three IGRT fractions predict future patient position with CBCT. The vertical, lateral, longitudinal, and total three dimensional setup uncertainty averages were plotted with +/- standard deviations for the first three days of treatment in black and all subsequent treatments in white. Student’s t-test was used to determine significance between groups.
Mentions: We next determined whether the first three days of IGRT would predict patient setup for subsequent fractions. Patients underwent CBCT for the first three fractions and remarked before the fourth fraction. As shown in Figure 1, there was no statistical difference (p = NS) in setup uncertainty between the first three days of treatment and all subsequent treatments via CBCT image guidance. We also analyzed post treatment images to quantify intrafraction motion. For 100 fractions, the mean difference from pre-treatment to post-treatment images was 0.7 mm.

Bottom Line: No reductions to targets occurred with individualized PTVs.Daily imaging allows application of individualized CTV expansion to reduce dose to OAR responsible for neurocognition, learning, and neuroendocrine function below doses shown to correlate with long-term morbidity.The demonstrated reduction in dose to OAR in this study has implications for quality of life and provides the motivation to pursue custom PTV expansion.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Brain Tumor Center, Norton Healthcare, Louisville, KY, USA. acspalding1@gmail.com.

ABSTRACT

Background: Image-guidance maximizes the therapeutic index of brain irradiation by decreasing setup uncertainty. As dose-volume data emerge defining the tolerance of critical normal structures responsible for neuroendocrine function and neurocognition, minimizing clinical target volume (CTV) to planning target volume (PTV) expansion of targets near these structures potentially lessens long-term toxicity.

Methods: We reviewed the treatment records of 29 patients with brain tumors, with a total of 517 fractions analyzed. The CTV was uniformly expanded by 3 mm to create the PTV for all cases. We determined the effect of patient specific factors (prescribed medications, weight gain, tumor location) and image-guidance technique on setup uncertainty and plotted the mean +/- standard deviation for each factor. ANOVA was used to determine significance between these factors on setup uncertainty. We determined the impact of applying the initial three fraction variation as custom PTV-expansion on dose to normal structures.

Results: The initial 3 mm margin encompassed 88% of all measured shifts from daily imaging for all fractions. There was no difference (p = n.s.) in average setup uncertainty between CBCT or kV imaging for all patients. Vertical, lateral, longitudinal, and 3D shifts were similar (p = n.s.) between days 1, 2, and 3 imaging and later fractions. Patients prescribed sedatives experienced increased setup uncertainty (p < 0.05), while weight gain, corticosteroid administration, and anti-seizure medication did not associate with increased setup uncertainty. Patients with targets near OAR with individualized margins led to decreased OAR dose. No reductions to targets occurred with individualized PTVs.

Conclusions: Daily imaging allows application of individualized CTV expansion to reduce dose to OAR responsible for neurocognition, learning, and neuroendocrine function below doses shown to correlate with long-term morbidity. The demonstrated reduction in dose to OAR in this study has implications for quality of life and provides the motivation to pursue custom PTV expansion.

Show MeSH
Related in: MedlinePlus