A methodology for incorporating functional bone marrow sparing in IMRT planning for pelvic radiation therapy

Background and purpose

The purpose of this study was to design a radiation therapy treatment planning approach that would spare hematopoietically active bone marrow using ¹⁸F]FLT PET imaging.

Materials and methods

We have developed an IMRT planning methodology to incorporate functional PET imaging using ¹⁸F]FLT scans. Plans were generated for two simulated cervical cancer patients, where pelvic active bone marrow regions were incorporated as avoidance regions based on the ranges: SUV4 ? 4; 4 > SUV3 ? 3; and 3 > SUV2 ? 2. Dose objectives were set to reduce bone marrow volume that received 10 (V₁₀) and 20 (V₂₀) Gy.

Results

Active bone marrow regions identified by ¹⁸F]FLT with an SUV ? 2, SUV ? 3, and SUV ? 4 represented an average of 43.0%, 15.3%, and 5.8%, respectively of the total osseous pelvis for the two cases studied. Improved dose-volume histograms for all identified bone marrow SUV volumes and decreases in V₁₀, and V₂₀ were achieved without clinically significant changes to PTV or OAR doses.

Conclusions

Incorporation of ¹⁸F]FLT PET in IMRT planning provides a methodology to reduce radiation dose to active bone marrow without compromising PTV or OAR dose objectives in pelvic malignancies.