3'-deoxy-3'-[¹⁸F]fluorothymidine PET quantification of bone marrow response to radiation dose

Abstract

Purpose: The purpose of this study was to quantify the relationship of bone marrow response to radiation dose, using 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT)-labeled uptake quantified in positron-emission tomography (PET) scans.

Methods and materials: Pre- and post-Week 1 treatment [(18)F]FLT PET images were registered to the CT images used to create the radiation treatment plan. Changes in [(18)F]FLT uptake values were measured using profile data of standardized uptake values (SUVs) and doses along the vertebral bodies located at a field border where a range of radiation doses were present for 10 patients. Data from the profile measurements were grouped into 1 Gy dose bins from 1 to 9 Gy to compare SUV changes for all patients. Additionally, the maximum pretreatment, the post-Week 1 treatment, and the dose values located within the C6-T7 vertebrae that straddled the field edge were measured for all patients.

Results: Both the profile and the individual vertebral data showed a strong correlation between SUV change and radiation dose. Relative differences in SUVs between bins >1 Gy and <7 Gy were statistically significant (p < 0.01, two-sample t test). The reduction in SUV was approximately linear until it reached a reduction threshold of 75%-80% in SUV for doses greater than 6 Gy/week for both the dose-binned data and the vertebral maximum SUVs.

Conclusions: The change in SUV observed in head and neck cancer patients treated with chemoradiation shows the potential for using [(18)F]FLT PET images for identifying active bone marrow and monitoring changes due to radiation dose. Additionally, the change in [(18)F]FLT uptake observed in bone marrow for different weekly doses suggests potential dose thresholds for reducing bone marrow toxicity.

Conflict of interest statement

Conflicts of Interest Notification: No conflicts of interest exist.

Copyright © 2011 Elsevier Inc. All rights reserved.

Figures

Figure 1

Pre- and 1 week post therapy [18F]FLT PET images registered to the radiation treatment plan for a head and neck patient. Lines indicate the planned radiation dose and the colorwash indicates FLT uptake with the color scale of red to blue representing SUVs from 6.5 to < 1.

Figure 2

The change in pre- and post week 1 therapy [18F]FLT PET SUVs due to radiation dose along a spine profile. As radiation dose decreases, the change in pre- and post week 1 therapy SUV decreases.

Figure 3

The average reduction in bone marrow [18F]FLT PET voxel SUV for 1 Gy dose bins from 1 to 9 Gy. The dashed line shows where the change in relative decrease in SUV between bins is no longer statistically significant.

Figure 4

A scatter plot of the reduction in bone marrow [18F]FLT PET voxel SUV as a function of radiation dose.

Figure 5

The average reduction in bone marrow [18F]FLT PET maximum SUV for the maximum dose in vertebrae C6 - T7 for 10 patients.